[From the U.S. Government Printing Office, www.gpo.gov]





















                                  TTLE MANATEE RIVER STUDY



                        A Characterization of Watershed Hydrology
                            and Investigation of Water Quality
                          and Nutrient/Solids Transport

                                       FINAL REPORT




                                        Sid Flannery
                       Southwest Florida Water Management District



                                     Herbert L. Windom
                                        Feng Huan
                            Skidaway Institute of Oceanography



                                        Ken Haddad
                         Florida Department of Natural Resources
                            Florida Marine Research Institute


                                         Edited by
                                      Gail M. Sloane
                                      Steve J. Schropp
                                     Fred D. Calder
                      Florida Department of Environmental Regulation

                                      March 23, 11390




                 Funds for this project were provided by the Department of
                 Environmental Regulation, Office of Coastal Management using
                 funds made available through the National Oceanic and
                 Atmospheric Administration under the Coastal Zone Management
                 Act of 1972-1, as amended.

















                                                               TABLE OF CONTENTS


                      EXECUTIVE SUMMARY . . . . . . . . . . . . . . . . . . . . .   iii


                      ACKNOWLEDGEMENTS  . . . . . . . . . . . . . . . . . . . . . .  vi                                     


                      I.   INTRODUCTION . . . . . . . . . . . . . . . . . . . . . .   1                                        
                           OVERVIEW OF THE LITTLE MANATEE RIVER WATERSHED PROJECT .   3


                      II.  DESCRIPTION OF THE WATERSHED . . . . . . . . . . . . . .   5
                           SIZE AND TRIBUTARIES . . . . . . . . . . . . . . . . . .   5
                           CLIMATE  . . . . . . . . . . . . . . . . . . . . . . . .   7
                           GENERAL RUNOFF CHARACTERISTICS . . . . . . . . . . . . .  10
                           GEOGRAPHIC INFORMATION SYSTEMS DEVELOPMENT . . . . . . .  16
                                Data Acquisition and Duality Contro . . . . . . . .  16
                                     Data Layers  . . . . . . . . . . . . . . . . .  16
                                     Tabular attribute data . . . . . . . . . . . .  20
                                     Quality Control and Assessment . . . . . . . .  20
                                     Data analyses  . . . . . . . . . . . . . . . .  21

                      III. WATER RESOURCES  . . . . . . . . . . . . . . . . . . . .  23
                           HYDROGEOLOGY . . . . . . . . . . . . . . . . . . . . . .  23
                           WATER USE PERMITS  . . . . . . . . . . . . . . . . . . .  24
                           FLORIDA POWER AND LIGHT WITHDRAWALS  . . . . . . . . . .  26


                      IV.     HYDROLOGIC CONDITIONS DURING THE STUDY  . . . . . . .  30
                              DATA COLLECTION NETWORK  . . . . . . .  . . . . . . .  30
                              RAINFALL. . . . . . . . . . . . . . . . . . . . . . .  34
                              STREAMFLOW. . . . . . . . . . . . . . . . . . . . . .  37
                              TIDES . . . . . . . . . . . . . . . . . . . . . . . .  43


                      V.      FRESH WATER CHEMISTRY . . . . . . . . . . . . . . . .  46


                              OBJECTIVES. . . . . . . . . . . . . . . . . . . . . .  46
                              SAMPLING AND ANALYTICAL METHODS . . . . . . . . . . .  46
                              OTHER DATA SOURCES. . . . . . . . . . . . . . . . . .  53
                              DATA REDUCTION  . . . . . . . . . . . . . . . . . . .  54
                                   Estimates of Annual Material Flux from Sub-Basins 54
                                   Extrapolation method for estimating material
                                        flux  . . . . . . . . . . . . . . . . . . .  56
                                   Interpolation method for estimating material
                                        flux  . . . . . . . . . . . . . . . . . . .  58



                              RESULTS   . . . . . . . . . . . . . . . . . . . . . .  61
                                   Water Quality Characteristics  . . . . . . . . .  61
                                   Chemical Transport from Sub-basins . . . . . . .  77
                                   Rating curves  . . . . . . . . . . . . . . . . .  77
                                   Fluxes from Sub-basins . . . . . . . . . . . . .  79


									i
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              VI.   ESTUARINE WATER CHEMISTRY . . . . . . . . . . . . . . . .     85
                    OBJECTIVES  . . . . . . . . . . . . . . . . . . . . . . .     85
                    SAMPLING AND ANALYTICAL METHODS . . . . . . . . . . . . .     85
                    DATA REDUCTION  . . . . . . . . . . . . . . . . . . . . .     90
                    RESULTS . . . . . . . . . . . . . . . . . . . . . . . . .     92
                         Salinity Distributions   . . . . . . . . . . . . . .     92
                         Dissolved Oxygen   . . . . . . . . . . . . . . . . .    104
                         General Water Chemistry  . . . . . . . . . . . . . .    112
                         Nutrient and Suspended Solids Distribution . . . . .    115
                               Dissolved Nutrients. . . . . . . . . . . . . .    115
                               Total Suspended Sediments and Particulate
                                     Nutrients  . . . . . . . . . . . . . . .    116
                         Chlorophyll, Phytoplankton and Primary
                               Productivity   . . . . . . . . . . . . . . . .    116
                               Seasonal Trends for Chlorophyll
                                     Concentrations and Phytoplankton
                                     Composition  . . . . . . . . . . . . . .    120

              LITERATURE CITED  . . . . . . . . . . . . . . . . . . . . . . .    128



									ii
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                                        EXECUTIVE SUMMARY


                    The Little Manatee watershed is located in southern
              Hillsborough and northern Manatee Counties.      The river generally
              flows in a westerly direction discharging to Tampa Bay near
              Ruskin.


                    Land use in the watershed was analyzed using a geographic
              information system. The entire watershed comprises 57,364
              hectares (224 square miles).    Upland plant Communities comprise
              13% of the watershed and consist of pinelands to hardwood
              forests.  Wetland plant communities constitute 9% of the
              watershed ranging from saltmarsh to hardwood swamp.       Water bodies
              comprise 3% of the watershed, not including the river and its
              tributaries.


                    The largest category under GIS land use is
              agriculture/pasture/barren, which constitutes 75% of the
              watershed.   This category is very general, and includes urban
              areas.  Urban areas represent a small portion of this percentage.
              This category is representative for subwatersheds except for the
              Cypress Creek subwatershed which includes the urbanized Sun City
              center area.


                    Streamflow and water quality in Carlton Branch, Dug Creek,
              Cypress Creek, the Little Manatee near Fort Lonesome, South Fork,
              and the Little Manatee near Wimauma were monitored during the
              study period from January 19Be through January 1989.

                    Bi-weekly water quality sampling during the study year found
              pronounced differences in water chemistry between the seven
              stream stations.    DOC and nitrate 'concentrations were highly
              variable during the study period.     Concentrations of ammonia and
              phosphate were somewhat less variable and reached maximum values
              between July and September.     This was the approximate time of the
              highest discharge.

                    Particulate carbon, nitrogen and phosphorus vary, in
              general, with total suspended solids. The maximum or spike in
              particulate substances for the Cypress Creek, Carlton Creel-.-.,
              Wimauma and Ft. Lonesome chemographs occur at the same time but
              are not present in the Dug Creek and South Prong chemographs.

                    The Fort Lonesome station was the most upstream site
              monitored on the main channel of the Little Manatee River.
              Generally, water quality at this site     can be characterized as
              highly colored, slightly acidic, with low levels of suspended
              matter and moderate levels of nutrients.      Mean values of color
              and total dissiolved carbon were highest at this station, probably
              reflecting the input of humi-z compounds leached from vegetation
              and litter in the drainage basin.

                                                iii











                   The site most similar to Fort Lonesome was the South Fork,
             which was the only station on that branch of the river.      Mean
             Values of alkalinity and chloride were ranked lowest for this
             station, and a number of parameters were ranked second lowest
             only to Fort Lonesome (conductivity, turbidity, total suspended
             solids, particulate carbon, particulate nitrogen, calcium and
             sul f ate) .For some other parameters (total dissolved carbon,
             ammonia, nitrate/nitrite, ortho-phosphate, and silica'.), the South
             Fork was ranked near the middle of the seven stations.


                   Of the remaining five stream sampling stations, two sites
             (LMR near WimaUMa and LMR North Fork) were on the main channel of
             the river while three stations were on three tributary creeks to
             the main channel.   These three tributaries, Carlton Branch, Dug
             Creek and Cypress Creek, all flow from north to south and enter
             the Little Manatee on its-, northern bank.   In general, water in
             these tributaries was lower in color and more highly mineralized
             than water in the main river or the South Fork.     Cypress Creek
             was notable for the high levels of turbidity, total suspended
             solids, particulate carbon and particulate nitrogen, probably
             reflecting the soil disturbance and    resulting suspended load that
             was generated in the sub-basin during the study.     Dug Creek and
             Carlton Branch had the lowest mean color values found in the
             study but had the highest levels of nitrate-nitrite and silica.
             It is believed that the high degree of mineralization and
             dissolved constituents in these three tributaries are the result
             of irrigation runoff.


                   The three stations on the main channel of the Little Manatee
             River are Fort Lonesome, LMR North Fork, and the LMR near
             Wimauma.   Examination of mean water quality values for these
             three stations demonstrates the increasing mineral and      nutrient
             content of the Little Manatee as it flows to Tampa Bay.      Some
             constituents, such as nitrate, silica, TSS and sulfate     show
             significant levels of enrichment proceeding downstream     while both
             particulate and dissolved phosphorus show little or no
             enrichment.


                   Salinity distributions in the estuary showed distinct
             changes in response to these changes in flow.     Mean water Column
             salinity was measured at four fixed locations in the river.
             Salinity at the mouth cif the river remained above 20 ppt until
             early September, when flood flows briefly reduced salinity to
             near 5 ppt.   For the remainder of the year, salinities fluctuated
             between 18 and 23 ppt salinity, with slight decreases in November
             and January due to storm events. Maximum observed salt
             penetration was in June, near the end cif the dry season.
             Salinity in the river decreased through July and AugUSt, and the
             river was completely fresh except for a small salt lens at the
             (nouth during a flood in early September.    By late September and
             through the fall, salinity distributions had returned to more



                                                iv











              typical profiles, although a significant storm event in January
              1989 freshened the river above mile five.


                  Dissolved oxygen concentrations in the Little Manatee River
              were at high levels during most of the year but reduced to values
              below 4 mg/l during much of the summer, indicating potentially
              stressful concentrat ions for aquatic biota in the summer.
              Differences in dissolved oxygen between surface and bottom waters
              were small, however, and it does not appear that oxygen stress
              occurs in bottom waters due to limited mixing.    Generally, with
              regard to temperature and salinity effects on water density and
              stratification, the Little Manatee tends to be well mixed.      There
              are areas of the river, however, that appear to be sensitive to
              factors that could reduce dissolved oxygen concentrations.

                  A progression from the upper reaches of the Little Manatee
              estuary to Tampa Bay showed chemical differences indicative of a
              change from nutrient-rich, low-salinity waters to phytoplankton
              dominated, high-salinity waters.   Nitrate-nitrite, silica,
              particulate carbon, turbidity, and total dissolved carbon showed
              distinct declines in concentrations from the upper reaches of the
              estuary to Tampa Bay.   With the exception of phosphorus, the bay
              has much lower levels of dissolved nutrients (N,,Si) due
              presumably to phytoplankt---)n uptake. Dissolved phosphorus
              concentrations were distributed very evenly along the salinity
              gradient indicating this nutrient is  not limiting and is in
              excess supply in the estuary.   Total suspended solids were
              highest in Tampa Bay, and increased with salinity in the river
              due to the influence of bay water.


                   The Ruskin Inlet station was located in an urbanized
              tributary to the Little Manatee that receives considerable
              amounts of urban runoff.   Of -:,.-jurse, salinity fluctuated MUCh
              r@ore at this station than at the stations located on specific
              salinity concentrati--nns. Nutrient cr-incentrations showed large
              seasonal variation at this station due to stormwater inputs and
              the rapid change from a meschaline (medium salinity) to a 1---tw
              salinity environment.


















                                               v
















                                       ACKNOWLEDGEMENTS


                  Watershed management has been an elusive concept to apply in
             protecting estuaries and their tributaries.    One of the reasons
             for this is the difficulty in obtaining physical, chemical and
             biological information on a scale needed to determine system-wide
             resource protection strategies.
                  The Little Manatee River Project demonE-:;trates that skilled
             people will go beyond their routine responsibilities in
             contributing to a team effort to make a large-scale Study work.
             In particular, the complex field and laboratory activities, of
             this project could riot have been conducted without the personal
             interest and pr----fessional help from.- Quincy Wylupek, Phillip
             Rhinesmith and Mark Rials of the Southwest Florida Water
             Management District.
                  Of considerable importance to watershed -5tUdies are good
             descriptions cof hydrological processes and upland features.    For
             assistance in providing these, special thanks are due to Dr.
             Bruce Taylor, P.E. (Taylor Engineering, Inc.), and Harry Downing
             (Southwest Florida Water Manaciement District).   We especially
             appreciate the help of Ken Butcher (United States Geological
             Survey) for his promptness in collecting stream flow information
             and establishing stream discharge statistics.
                  Funded by NOAA through the Coastal Zone Management Act, as
             amended









































                                              vi












                           I. INTRODUCTION




                              This is a report on water chemistry and hydrology in the

                           Little Manatee River, its tributaries, and estuary. The results

                           presented in this report deal mainly with characterizations of

                           the movement of nutrients, solids and major ions through the

                           system. The report also includes a brief physiographical

                           description, including vegetative cover, land use, soils, and,

                           climate to support finding on the origin, transport and removal

                           of chemical constituents and solids carried by the river.

                              This document, along with separate biological reports-

                           (Peebles,1989),(Rast, 1989),(Vargo, 1989)-are the result of

                           efforts by the Southwest Florida Water Management District

                           (SWFWMD), Florida Department of Environmental Regulation (FDER),

                           and Florida Department of Natural Resources (FDNR) to develope a

                           system-wide understanding of resource management needs for the

                           Little Manatee River basin. These reports are basic information

                           sources to be used in identifying man's influences on the river,

                           estimating possible degradation of the aquatic system, and

                           understanding the susceptibility of the system to future

                           problems.

                              SWFWMD, FDER and FDNR` initiated this project in response to

                           agency and public concern over protection of the last major river

                           in a relatively natural condition in the Tampa Bay system. The                                                                     

                           protection of the Little Manatee River and estuary is a state


                           priority. The river, in addition to its own resource values 


										1
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			influences water, quality and habitat in Tampa Bay including the

			adjacent Cockroach Bay Aquatic Preserve. Because of the lack of
		
			urbanization in the basin, there is opportunity to develop a
	
			comprehensive strategy to anticipate and prevent problems as the

			basin is developed.

				Activities to protect and re-establish living resources in

			Tampa Bay cannot be fully effective without protecting the Bay's

			tributaries and their associated wetlands. Drainage basins with

			natural systems relatively intact, such as the Little Manatee

			River basin should be managed as ecological and hydrological

			units. This comprehensive approach is the only effective way to

			ensure that proper freshwater flows and nutrient inputs are

			maintained in the estuarine part of the system.

				As in many coastal systems the existing information on the

			Little Manatee River and estuary was not on system-wide

			processes. While localized data is useful for individual

			regulatory decisions, larger-scale studies that integrate

			physical and chemical information are essential for judging the

			susceptibility of the river to development pressures,

			establishing sound management objectives and plans, and providing

			development criteria for maintaining conditions that support

			estuarine productivity.



									2







		OVERVIEW OF THE LITTLE MANATEE RIVER WATERSHED PROJECT



			Prior to initiating the study, we consulted with local,

		state and federal agency representatives to determine the extent

		of existing information on the system and to help establish a

		master plan and detailed sampling and analytical methods. During

		discussions between the project team and persons with local

		knowledge of the river, the following concerns were expressed:

				1.  Upstream impoundments and water diversions have

			decreased the estuary's value as a fishery nursery;

				2.  Nutrient enrichment has resulted from agriculture

			and aquaculture operations in the watershed;

				3.  Future development in the watershed may increase

			erosion and contribute to increased sedimentation and

			nutrient enrichment;

				4.  Land use planning agencies do not have sufficient

			information to adequately protct watershed features and

			natural processes; and

				5.  Finfish and shellfish yields have decreased.

			During the prelimanary stage, the U. S. Geological Survey,

		under contract with DER installed stream flow recorders on

		subwatersheds in preparation for chemical and hydrological

		measurements on the major system compartments.

			After initial testing of field and laboratory methods,

		formal work began in January 1988. The last field measurements



									3








			included in this report were taken January 1989, although

			monitoring will continue on a less intensive basis.

				The SWFWMD conducted the field program, the majority of the

			laboratory work, and assisted in interpretation of the data.

			Supplemental laboratory analyses were done by commercial

			laboratory.  The Department of Natural Resources Marine Research

			Institute provided mapping and descriptions of land features,

			land usage and drainage patterns. The Department of

			Environmental Regulation provided technical assistance on

			establishing methodology and interpreting chemical and physical

			measurements.













										4










           II.   DESCRIPTION OF THE WATERSHED


           SIZE AND TRIBUTARIES

			The Little Manatee watershed is located in southern

		Hillsborough and northern Manatee Counties. The Little Manatee

		River is about 40 miles in length with a contributing drainage

		basin of about 221 square miles (Figure 2.1). Headwaters for the

		river are in a swampy area of southeastern Hillsborough County.

		The river generally flows in a westerly direction discharging to

		Tampa Bay near Ruskin. The river channel is usually well defined

		except in the most upstream areas. The lower 10 to 15 mile reach

		of the river is tidally influenced.

			Major tributaries to the Little Manatee River include

		Cypress and Dug Creeks located in the northwestern portion of the

		basin; Gully, Carlton, and Pierce Branch located in the north-

		central portion; Howard Prairie Branch and Alderman Creek in the

		eastern portion; South Fork in the south-central portion; and

		Wildcat and Curiosity Creeks in the western portion of the basin.

		Streamflow and water quality in Carlton Branch, Dug Creek,

		Cypress Creek, the Little Manatee near Fort Lonesome, South Fork,

		and the Little Manatee near Wimauma were monitored during the

		study period from January 1988 through January 1989. Details







										5







           Little Manatee River
           Drainage Basin




                                                                                                       )C3
                                                             4
                                               B           x
                                                                         E         G

                                          x
                                                       A


                                                                                            ........ ..
                                                  F

                                                                                                             6x





                                                2 X


                  A e USGS Streamflo                 sites
                                         w gaging                                                 x                             z
                   X Rainfall stations                                                                                          L/5
                                                                                                                                LK
                                                                                                                                C)









                                                                                                                         L


     Figure 2.1.    Tito Little Manatee River Drainage basin.










		presented in Figure 2.2. Most of the rainfall occurs during the

		summer months. Tropical storms and convective thunderstorms are
		
		the main reason for the higher precipitation rates in the summer

		months.



					RUSKIN AVERAGE MONTHLY RAINFALL (1976-1989)




















		Figure 2.2.   Distribution of the monthly average annual rainfall for the
				  Ruskin station (1976-1989).



			Another important aspect of the climate that effects runoff

		is evapotranspiration. Evapotranspiration is the process whereby

		incoming energy from solar radiation transforms water from a

		liquid to a gaseous state. The processes involve direct

		evaporation of water from moist surfaces and transpiration during

		plant respiratory processes. There are two types of



								8









			evapotranspiration (ET) estimates: potential and actual.

			Potential ET is the maximum ET expected under prevailing climatic

			conditions assuming non-limited water availability. One of the

			most accurate methods for estmating potential ET is the Penman

			method. The method considers cloud cover, temperature, vapor

			pressure deficits and incoming solar radiation. For the Tampa

			area, the 50 percent probable potential ET is 54 inches

			(Smajstrla, 1984), which is close to the average annual

			precipitation for the area.

				Actual ET, on the other hand, is the amount of water

			transformed based upon prevailing climatic conditions and the

			amount of available moisture. Actual ET is very difficult to

			estimate because of its dependency on numerous factors. Such

			factors include land cover, distribution of rainfall, surface

			water storage, and soil percolation. Since the basin exhibits

			very little ground water recharge or discharge into the aquifer

			system (Aucott, 1988), the actual ET rate can be approximated by

			rainfall minus runoff. If the average annual rainfall is taken

			as 50.5 inches/year and the average annual runoff depth at 15.6

			inches/year, the actual ET estimate is 34.9 inches/year. This

			estimate is probably low because of the irrigation runoff within

			the basin. The USGS has estimated actual ET in the region at 39

			inches/year.





											9









			GENERAL RUNOFF CHARACTERISTICS

				A one-hundred forty-nine square mile area of the Little

			Manatee River watershed has been monitored for runoff at a USGS

			gaging station since 1939. This USGS strean gaging station

			(#02300500) is located on the Hwy. 301 bridge near Wimauma 15

			miles upstream from the river's mouth. Daily records for this

			site are available for a period of about 50 years which provide a

			good statistical base for establishing characteristic flow

			patterns for the watershed.

				Average monthly discharges for the period of record
	
			available for the Wimauma station are presented on Figure 2.3.

			July through September represent the highest runoff months with

			average discharges between 300 and 400 cubic feet per second

			(cfs).


						WIMUAMA AVERAGE MONTHLY FLOW (1939-1989)

					450

					400

					350

					300
		
					250

					200

					150

					100

					 50

					  0   JAN  FEB  MAR  APR  FEB  MAY  JUN  JUL  AUG  SEP  OCT  NOV  DEC
											  MONTH

			Figure 2.3.  Average monthly flows for Wimauma station (1939-1989).


												10










			The remaining months of the year averaged 150 cfs or less.

		Pronounced low flow periods usually occur in the late spring

		(May) or the late fall and early winter (November and December).

		The average discharge for the 149 square mile area is 171 cfs.

		In terms of depth of water over the contributing watershed, this

		flow represents 15.6 inches of runoff per year. Along with the

		Alafia basin, the Little Manatee basin has the largest runoff

		depth of any basin located within west-central Florida (15 to 20

		inches/year) (USGS, 1981).

			A review of historical flow records for the Wimauma site

		reveals extreme seasonal and yearly variations in discharge. The

		largest instantaneous flow of record is about 14,000 cfs which

		occured in June 1960. The lowest flow of record is about 0.8

		cfs which occurred in December 1976. Table 2.1 represents a

		duration analysis of discharges at the Wimauma monitoring

		station. Between the 95 and 5 percent exceedance probabilities

		flows varied between 10.0 and 708 cfs, with a median of 54 cfs.

		This median flow is less than the average flow for this station

		by more than a factor of three, indicating that the average

		statistic is heavily influenced by brief periods of high runoff.

			Based on a review of historical runoff events and the

		duration analysis, it appears that the runoff hydrographs are

		very peaked or ephemeral. This type of runoff pattern indicates

		the absence of significant surface water storage areas that can

		moderate discharges by attenuating flows. For example, the

		Withlacoochee River system drains an area greater than 2000


								11









		Table 2.1.  Wimauma Flow Duration Table.


						Wimauma Flow Duration Table

		Exceedance						Exceedance
		Probability			Flow			Probability			Flow
		    95.0			10.5				45.0			  67.5
		    90.0			15.6				40.0			  75.3
		    85.0			20.0				35.0			  89.3
		    80.0			23.6				30.0			 109.7
		    75.0			27.2				25.0			 140.3
		    70.0			31.9				20.0			 185.2
		    65.0			36.6				15.0			 257.2
		    60.0			42.0				10.0			 400.6
		    55.0			47.4				 5.0			 708.3
		    50.0			55.3


		square miles; however, the highest recorded discharge near the

		mouth of that basin has been less than 10,000 cfs. This is

		because the associated lakes, sloughs, and swamps in the

		Withlacoochee basin provide significant attenuation of peak

		flows. This is in contrast to the Little Manatee River at the

		Wimauma USGS gaging station which has a drainage area of 149

		square miles but a recorded peak discharge of 14,000 cfs.

			During the study period several days of significant rainfall

		occurred over the basin yielding a peak discharge of 9700 cfs.

		This represents a discharge event with a probability of

		occurrence between one-in-10 to 25 years. As previously

		indicated, the largest instantaneous flow of record for the

		Wimauma station was 14,000 cfs. This represents a discharge

		event with a return frequency of one-in 50 years. Table 2.2

		represents expected high discharges for various return intervals.




									12









			Table 2.2.   Flood Flow Return Frequencies (D&M, 1975)



				Return Interval Years				Flow @ Wimauma

					100							18,550
					 50						 	14,800
					 25							11,560	
					 10							 7,930
					  2.33						 3,300

			Results of low flow frequency analysis for the Little Manatee

			River near Wimauma are presented in Table 2.3. This table shows

			that the river has prolonged periods of low flows. For instance,

			a thirty-day period of average flow less that 13 cfs has a return

			frequency of every two years. The lowest daily flow of record

			(0.8 cfs) has a return interval greater than one-in 20 years.

			Florida Power and Light (FP&L) has a large pumping station on the

			Little Manatee River that is used for make up water for their

			power generating facility which went into operation in 1976. It

			is expected that this withdrawal will have little impact on

			exteme low flows because of withdrawal limitations by agreement.

			
			Table 2.3.		Low-Flow Frequency Wimauma


			Consecutive				Return Frequency in Years

			Day			2			5			10			20

			  1		    7.9		    4.1			2.7			1.9
			  3		    8.3		    4.4			3.0			2.1
			  7		    9.1		    4.8			3.2			2.3
			 14		     10		    5.7			4.1			3.1
			 30		     13		    7.6			5.8			4.7




										13









				The next longest term gaging station (#02300100) within the

			basin is the Little Manatee River near Fort Lonesome. The

			station monitors discharge from a 31.4 square mile basin located
	
			in the northeast section of the Little Manatee watershed which is

			within the 149 square mile area monitored by the Wimauma station.

			The monitoring station is located near the Hwy. 674 bridge 31

			miles upstream from the Little Manatee River mouth. The station

			was installed in 1963 and has been continually operated since

			that time, providing about 25 years of daily discharge data.

				A review of the historical flow records reveal the same

			extreme variations in flow as noted at the Wimauma station. The

			largest instantaneous flow of record is 3100 cfs which occurred

			in September 1979. The minimum flow is zero and it occurs quite

			often. Average monthly discharges for the period of record at

			Fort Lonesome are presented on Figure 2.4. July through

			September represent the highest runoff months with average

			discharges between 50 and 80 cfs. The remaining months of the

			year average from 30 to slightly below 10 cfs. Similar to the

			Wimauma station, the lowest average monthly flows are observed in

			the late spring and late fall. The average discharge for the

			basin is 29.6 cfs. In terms of depth of water over the

			contributing basin, this flow represents 12.80 inches of runoff

			per year. This is significantly less than the Wimauma runoff

			depth by about 20 percent. This difference in runoff depth would
		
			indicate that the hydrologic conditions within the basins are



								14

















                                                                            t- j.






                                FORT. LONESOME AVERAGE MOM-HLY FLOW (.1963 - 1989)


                                To






                                30 -
                           cn

                           U
                                40
                           3:
                           0
                           U-   an -



                                                                    IN




                                  JAN FEB MAR APR MAY    JUN JUL AUG:SEP  OCT NOV DEC
                                                            WONTH





                 Figure 2.4.      Average monthly flow for Fort Lonesome station           (1963-1989).


















                                                                                P



                                                                       THIS
                                                                            MATERIAL SUCJEC7' TC) nEVtS10tv










		GEOGRAPHIC INFORMATION SYSTEMS DEVELOPMENT

			The development of a GIS database is complex, dynamic and

		requires data acquisition from many sources. Since the future

		analyses to be conducted with GIS will quantitative, it is

		imperative that cartographic integrity be maintained. This

		constraint has inhibited data entry, but results of maintaining

		this approach will have long-term benefits.

			Figure 2.5 depicts some of the layers of data being input to

		the Marine Resources Geographic System (MRGIS). These layers

		represents data identified as available in map form, or that can

		be generated from area photography or satellite imagery.

			The base map (data layer to which all other layers are

		referenced) consists of an April 1988 SPOT satellite panchromatic

		image geo-referenced to 7.5 minute U.S.G.S. quandrangles in a

		Universal Transverse Mercator (UTM) projection. The MRGIS data

		layers are currently in raster format, although we can accept

		vector data or convert raster data to vector for various analyses

		or for data distribution.


		Data Acquisition and Quality Control

			Data Layers. Numerous problems have been encountered

		generating appropriate overlays. Some data sources, problems and

		solutions are depicted in Table 2.4. It should be understood

		that many of these databases were not created with GIS entry in

		mind and do not have the cartographic integrity of a

		photogrammetrically developed map. Problems have been compounded



								16








                                                      7E SENSING
                                base Map         REMO I


                             Panchromati c            REMOTE SENS ING
                                  I ilia zi e

                                  Land                   REMOTE SENSING
                                      19
                                     Land Cover             REMOTE SENSING
                                         1982
                                         Land Cover            REMOTE SENSING
                                              1938

                                                                   REMOTE SENSING
                                                 Soils

                                                 Elevation            REMOTE SENSING


                                                   Flood Zones


                                                       Future Land            REMOTE SENSING
                                                            Use


                                                            Drainage


                                                            7ransportation


                                                                  Public Lands


                                                                     urisdic-, '-ion&]
                                      Tabular d  ata          TIJ     boundaries
                               Water puzilliTy 'parameters
                               Fisheries data                             Hy d r ol o gy
                               Fla. Nptu-al Areas Inventory
                               Perini tted discharges
                               Hydrological parame-Lers                       7-t-cetera
                               Sol Is attributes


                     rigure       Some oC the data layers bakng im-plemented cn the
                                  for rl)L     wazershecl.   1hose Inyers cepencient c..i reMoUe
                                  sensin3 are i)oz:ed.   1'abular datta r-o be linked to t;he cia@:a
                                  layers are Z16c, ncz@n@l.













           DaLa T-;:)e                    Snt!rce                   Problems                                   soluLions

           Base Mal)               SPOT P_@ncromatic                Geo-referencing to                         Careful selection 4)f control points
                                     satellite data                 1:24,000 USGS Quads.                       to reduce spatial. errors found on
                                                                                                               USGS quads

           1950/1980               FDNIR & USFOS aerial             30 Mqi@ic,-daEa                            rasi-_,npled to 10 mecer da@_a
           ],and cover             Photography

           1988 Land cover         SPD.T Multi- spectral            Statistical analyses                       Incorl)orate T4 satellita daLa in
                                   satelLite imagery.               difficult at 10 meter                      both Ole                 analyses phase
                                                                  -spatial resolution                          and 1-11terpretavion phase. Use WHAP
                                                                                                               coloi:-IR aerial lAiotography.

            a i I S                Soil Comer,.atiort Ser-          Soils delineated on photo-                 Soils scientist re-cowpile soils
                                   vice & Manatee County,           based separates are not carto-             maps onto 1:24,000 USGS OLIaOS. Scan
                                   Fl.                              graphically accurate.

           I'levation              USGS Quads and Southwest         5 Et- contours from LISGS Quads            Accent resolution of USCS data or
                                   Fla. Vater Hanaoment Dis-        are not adequate in a low re-              di-iLize SWFORD waps
                                   trict (SWD.119))                 lief watershed. SWII@V", has (in-
                                                                    digitized I & 2 ft. contours

           Flood Maps              Federal Emergency Manage-        Cartographically inaccurate-               Use 3 poi-nL trian!@ulauian to
                                   ment Agency                      and very general spatially'                dil&_;@ti_-e.

           FLI'Lre land-           11illsborough and Manatee        Cartographically inaccurata                Use 3 point triangulation. Cross-
           Use plans               Counties                         and different classification               reference classification system
                                                                    schemes -


                                   Aerial -].@,@_ography            Time consuming interprecacion              Holle
                                            r

           Ta b 1, e   Sources ,   problems, and solutions for some of clie data
                       layers being entered cr, the HRGIS for rhe UIR.










			by the fact that rectified SPOT data were more spatially resolved

			than National Map Accuracy Standards for 1:24,000 maps, making

			geo-referencing difficult and creating overlay problems at common

			borders (for example, shorelines defined by soils vs. land-use

			vs. flood zones). Furthermore, many data are in scales smaller

			than 1:24,000, compounding overlay difficulties. This does not

			present a problem if the limitations of the analyses are

			understood. For example, the future land-use data, if originally

			developed by the county at a 1:100,000 scale, cannot be applied

			to individual zoning issues at a parcel level, but could be used
	
			to project land-use changes over larger portions of the

			watershed.

				Complete watershed coverage has been built for flood zones,

			future land use, and general land cover for 1988. The estuarine

			portion of the watershed has land cover for 1950 and 1982

			completed. The status and specific problems with several

			remaining data layers are as follows:

				1. Soils: Soils data have been compiled by the Soil

			Conservation Service, and scan digitized for the LMR portion of

			Hillsborough County. Those data are in the MRGIS and being

			corrected and quality checked. Data are currently grouped by

			U.S.G.S. quad. Joining the quads (edge matching) to provide a

			continuous watershed coverage has proven difficult due to the

			complexity of soils polygons. Soils quads for the Manatee county

			portion of the watershed have been joined to form a continuous

			coverage. Based on preliminary observations, it appears that



								19









		merging soils data from Manatee and Hillsborough Counties will be

		challenging.

			2. Elevation: The Southwest Florida Water Management

		District is providing this data layer. We are currently

		developing methods and formats for data transfer.

			3. Drainage: This data layer is the most tedious effort

		for compilation, National High Altitude Program (NHAP) photos

		(1:50,000 scale) have been enlarged to 1:24,000 scale and

		detailed drainage line work is being interpreted. This type of

		interpretation has not been done for many areas in the U.S.,

		particularly at the resolution being attempted for this program.

		For example, individual drainage ditches within agricultural

		fields are being identified, along with their connection to

		tributaries of the watershed. This will allow better analysis of

		sources of waterborne constituents and will allow network

		analyses.

			4. Land cover/Land use: A land cover layer has been

		developed for the entire watershed by the Florida Game and

		Freshwater Fish Commission in cooperatin with the Florida Marine

		Research Institute (FRMI). These data are for 1987 (from Landsat

		Thematic Mapper) and provide a first look at land cover from a

		habitat and runoff potential. A 1988 SPOT image is being used to
		
		complete a detailed land use coverage. The land use data are

		being compiled at a 0.1 hectare resolution.

			5. Watershed and Subbasins: This data layer has been

		digitized from maps provided from the SWFWMD. The boundaries are

		

									20









			inaccurate in some areas because the basins were originally

			deliniated in the 1970's. Substantial changes have occurred in

			the drainage characteristics of the watershed since then.

			


				Tabular attribute data. Tabular data, such as soils

			definitions, bald eagle nesting locations, station locations and

			all associated water quality or fish distribution data, permitted

			effluent charges, and other digital data that represent a

			singular geographic location are also required for analyses. The

			biggest problem in working with these data are positional in

			accuracies and data exchange formats.



				Quality Control and Assessment. Data quality control and

			assessment are extremely important in the generation of the GIS

			layers and their tabular attributes. The two components of

			concern are cartographic integrity and data accuracy (is it where

			it should be and is it being called the right thing?). When

			accessing databases outside the control of FMRI, these issues are

			often difficult to assess prior to data entry. When we have

			control, such as in the soils digitization, we have taken extreme

			measures to insure cartographic integrity but can only accept the

			SCS's ability to properly identify soils. In most cases accuracy

			assessment of the information has nor been completed by the

			parent organization. For data being developed at FRMI, such as

			land use, statistical analyses of classification errors are being

			conducted.



										21









		Data analyses. Numerous test analyses have been conducted on

		portions of the watershed with many data layers. Only results of

		analyses specific to water quality data will be presented. The

		specific analyses addressed the issue of what land covers

		comprise the drainage area (subwatersheds) of each seven water
	
		quality stations. This type of information, in conjunction with

		other data layer information, can be used to assess the

		contribution of runoff to water quality findings. Table 2.5

		summarizes the general coverage, in hectares, for each of the

		water quality stations depicted in Figure 2.1. It should be

		noted that subwatersheds are difined by U.S.G.S. Criteria.

			The entire watershed comprises 57,364 hectares (224 square

		miles). Upland plant communities comprise 13% of the watershed

		and consist of pinelands to hardwood forests. Wetland plant

		communities consititute 9% of the watershed ranging from saltmarsh

		to hardwood swamp. Water bodies comprise 3% of the watershed,

		not including the river and its tributaries.

			Agriculture/pasture/barren constitute 75% of the watershed.

		This category is very general, and includes urban areas. Urban

		areas represent a small portion of this percentage, and will be

		well defined in the detailed land use layer. In Table 2.5 this

		category is representative for subwatersheds except at ST7 which

		is the urbanized suncity center area.

			Within each of the subwatersheds, the dominant land cover is

		agriculture/pasture/barren with a high of 90% at ST2 and low of

		



								22











                                                            t         t h c a                                 j.                w    t h        mia I
                                                                                                  i ri


                           V.)     C`Fli t Et 1.1 E` f P &.1, E. t U V F.  At    S-   f.1 t f i    o v   r a cl F..,i    d c- m j. r-) t. C., db y

                            barren,         represent i rig Ur ban                    and Use.






                                                  'Up I and                  Wetland                                 AF r i cul t ur e
                                                  Plant                        Plant                                      Pasture
                          Station              Communities                C; omrmm i t i e s         Water               Barren                   Total



                          ST1                        624                          718                   208                  6,577                6,127

                                                     i5i                            61                     1                 1,848               .2,061

                          ST3                     4,281                        1,527                    2.26                17,169              231,203

                          ST4                     2,531                        1,060                     47                  6,249                9,887

                          ST5                          77                           79                   26                      862              1,044

                          ST6                    6 , 515                      3 115                  1,684                  27,989               39,303

                          ST7                         127                                                42                  1,636                2 , 146
                                                                                                                            (urban)





                                     -jo@                                         A G            IJ-) t     -.Y I' o










		III. WATER RESOURCES

			Local water resources in the Little Manatee River basin are

		used extensively for agriculture and other consumptive purposes.

		A brief summary of factors pertaining to water resource

		utilization in the basin is presented below.



		HYDROGEOLOGY

			Most of the Little Manatee River watershed is overlain with

		a deposit of undifferentiated sands that vary in thickness from

		less than 25 feet along the coast to greater than 50 feet in the

		eastern portions. The Bone Valley Formation, which is comprised

		of a mixture of phosphatically enriched clays, limestone and

		sands, underlies these sands in certain areas. The

		undifferentiated sands also overlay the Hawthorn Formation which

		varies in thickness from less than 200 feet to more than 350

		feet. Below the Hawthorn Formation are the water bearing

		limestone formations of the Floridan aquifer system. Vertical

		movement of water through the Hawthorn Formation to the Floridan

		aquifer, termed recharge, is slow. The estimated recharge for 

		the area is 0-1 inches/year (Aucott, USGS 1988).

			Due to impeded vertical movement of water in the Little

		Manatee watershed, the area has characteristic high water tables

		and runoff potentials. Agriculturalists in the area have 

		maximized the utilization of the high water table condition for

		some of their farming operations. For example, vegetables are


							24




irrigated by managing the water table within close proximity of

the root zone.  Soil capillarity will then pull the water into

the root zone of the crop providing a stabilized environment.

Large quantities of groundwater are required to raise and

maintain the water table due to irrigation inefficiencies.


WATER USE PERMITS

	The Southwest Florida Water Management District (SWFWMD)

permits water use within a 16 county area which includes the 

Little Manatee River watershed.  Most of the water used within

the watershed is withdrawn from the Floridan aquifer. Figure 3.1

indicates the location of 200-plus production centers that each

withdraw 100,000 gallons per day or more.  Most of the water

withdrawn is used for irrigation.  As demonstrated by the density

of squares, most of the withdrawals are concentrated in the

northeastern and north-central portions of the watershed.











					25

 














                                                                                                                                      :zr ".0





                                                            J-)b



                                                                                                                                               ILI



                                                                           Viu
                                                                                                                   'YQ


                                                                      @6 A                                                      I-A






















                                                                                                              Out.
                                                                                    ume per                                      J@GlaL*tc     tlve-r basi-Et.


		FLORIDA POWER AND LIGHT WITHDRAWALS

			Lake Parrish is a man-made, off-stream reservoir adjacent to 

		the Little Manatee River in Manatee County that was constructed

		by FP&L in 1975. The reservoir is located in the south-central

		portion of the basin and occupies about 4,000 acres. The storage

		capacity of the reservoir is 48,000 acre-feet or 15.7 billion

		gallons. The reservoir is used as a cooling source for the FP&L

		electric power generating facility. A diversion channel

		transports water from the Little Manatee river to pumps that 

		discharge into the reservoir. A Southwest Florida Water

		Management agreement allows up to a 47 percent diversion of river

		flows that are above 40 cfs except during the months of August

		and September. During August and September, flows above 112 and 

		97 cfs may be diverted, respectively.

			Make-up water is required to counteract losses from the 

		reservoir from groundwater seepage and evaporation as the result 

		of heat addition from the power plant and sun.  The average

		pumpage rate into the reservoir since construction has been 11.5

		cfs or 7.4 million gallons per day. Pumping at this rate for a 

		year yeilds 17.2% of the total volumetric capacity of the 

		reservoir. The largest withdrawal amount for any year has been

		4,468 millions gallons during 1987, which represents 28.5% of the

		total reservoir capacity. During the 1988 study period, 2,407

		million gallons of water were pumped to the reservoir.

			The average pumping rate of 11.5 cfs represents 6.5 percent

		of the average flow at Wimauma during the period of operation.


							27 

		Monthly values of pumping to the reservoir and streamflow at the 

		Wimauma station are plotted for the period January 1979 to 

		October 1989 in Figure 3.2.a.  Diversion rates during this period

		are summarized by month in Table 3.1.  Actual diversion

		quantities are greatest in July and August while percentage flow

		reductions are greatest in January and May through July.


	Table 3.1. 		Average pumpage from the Little Manatee River
				(cfs) and the percentage of flow at the LMR near
				Wimauma gaging station, 1979 to 1989.


							Month
		J	 F	 M	 A	 M	 J	 Jy	     A	S	O 	N	 D
	Pumpage (cfs)
	    10.9    8.2   13.1  5.0   11.3  11.1   22.9    22.3   12.9   4.7    4.8   9.1	
	Per cent of Flow
	    10.2    6.8   9.2   4.6    9.5   9.0   14.7     7.7     5.7  9.9     5.1  8.4
	     J       F     M     A      M     J     Jy       A       S    O      N     D


		Daily pumpage to the reservoir and daily flow rates at the 

	Wimauma gaging station are showm for the study year in Figure

	3.2.b. Pumpage from the river was very small from January

	through June 1988. Then, significant quantities were pumped from

	the river from July to early September.  Pumpage ceased from mid-

	September through October, but resumed for a period of frequent

	pumping from November 1988 through January 1989.

		Since operation, FP&L's withdrawals from the river have been 

	characterized by intermittent withdrawals with a high degree of 
	
	short-term variation in quantities. For instance, during a 28-
	
	day period from December 12, 1988 to January 8, 1989, pumpage


						28




                               Figure 3.2.                      Daily            and monthly (A; pumpage of water from the Little
                                                                Manatee kiver and corresponding flows at the LMR near Wima
                                                                gaging station.



                                                                                  pUMpRG-         i AND WIMAUMA, DISCHARGE
                                                                     FPLL                        r-
                                                     j200 -                     AVERAGE MONTHLY VALuEs

                                                     1000 -


                                                     Boo        -


                                                     800        -


                                                     700        -
                                              cn
                                              U-
                                                     Soo        -


                                              LLJ    500        -

                                              Ly
                                                     400        -


                                              (n     300        -


                                                     200        -


                                                     100        -
                                                     o                           lei laz'83184 185                              86187 Ile les

                                                                                                  YEARS





                                                                                                                                                                                                      z
                                                                                                                                                                                                      .0



                                                                               FPLL pUnppCE AND DISCHARCE AT WIMRUMR


                                                                                                                                                                                                      LU
                                                                Soo                                            2050
                                                                                                                                                                                                      DO
                                                                                                                                                                                                      :D
                                                                                                                                                                                                      V)

                                                                300                                                                                                                          'U       <

                                                                                                                                                                                                      <

                                                                '00
                                                                                                                                                                                                      Ln



                                                     ui
                                                                300


                                                                ZZ 0


                                                                200


                                                                150


                                                                100


                                                                50


                                                                     DEC    JFIH,  FEB   IIAR   APR   nRy   JUH    jUL    MUC   SEP    OCT   )I Ov  DEC    JAH

                                                                                                    13EC- Be - JRK. SE


		averaged 22.6 cfs or about 48 percent of the average daily flow

		near Wimauma for that same period.  By contrast, during the

		previous twent-six day period when average daily flows in the

		river were more than twice as high, pumpage averaged only 10.3

		cfs or 9 percent of average flow.  It is not known why these

		differences in pumping rates were done by the Utility over this

		short-term period. One objective of the Little Manatee River

		Project is to recommend a withdrawal schedule based on 

		probability analysis that meets the Utility's need for make-up

		water while better interacting with the inflow needs of the 

		downstream riverine and estaurine ecosystems.






						30



		IV.  HYDROLOGIC CONDITIONS DURING THE STUDY



		DATA COLLECTION NETWORK

			The collection of hydrologic data is essential for

		understanding the relationships of land use to runoff and water

		quality in the Little Manatee River basin. For this project,

		existing USGS stream gaging stations and District rainfall sites

		were utilized in addition to new data collection sites

		established for the study. Figure 4.1 is a map showing the

		location of streamflow gaging and rainfall data collection sites

		used during study year (January 1988 to January 1989). A

		continuous water level was also installed at the mouth of the 

		river to record tide stage fluctuations.

			The most downstream stream gaging station on the main stem

		of the Little Manatee River (LMR) is LMR near Wimauma (station F,

		Figure 4.1). The USGS has collected continuous streamflow data

		at this station since 1939, giving 50 years of daily record. Two

		other gaging sites in the basin, LMR near Fort Lonesome and 

		Cypress Creek, are part of the regular USGS stream gaging

		network. The Fort Lonesome gage, with a corresponding drainage

		area of 31.4 square miles, measures flow from the upper-most

		reaches of the Little Manatee River basin. Data collection at

		this site began in 1963, giving 26 years of record. The Cypress

		Creek station, with a drainage area of 8.1 square miles, measures











							31







         'Little Manatee River
         'Drainage Basin




                                                                                                          X3
                                                            X4-
                                                                                     G
                                         IX            q




                                                                                                                6X





                                                2 X


                 A   USGS Streamf low gaging sites                                                   x
                  x Rainfall stations





      Figure 4.1..   Location of stream gaging and rainfall data collection sites in the Little Hanatee River
                     basin during the study year (January 1988 to January 1989).















               Figure 4.1.    (Key)



               Stream zazinz sites



               A.   Dug Greek
               B.   Cypress Creek

               D.   LMR South Fork

               E.   Carlton Branch

               F.   LMR near Wimauma

               G.   LMR near Fort Lonesome



               Rainfall sites



               1.   Ruskin

               2.   Florida Power and Light

               3.   Fort Lonesome

               4.   Wimauma

               5.   Fort Green

               6.   Four Corners


	flow from the smail sub-basin that includes the residential

	development of Sun City Center.

		Three new streamflow sites, LMR South Fork, Dug Creek and

	Carlton Branch, were established for the duration of the project.

	Continous streamflow at all sites was monitored by personnel of 

	the USGS Tampa office. These sites were established to examine

	rainfall-runoff relationships in discrete sub-basins of the 

	Little Manatee River basin. Data collection at these  three sites

	began in either December 1987 or January 1988, and concluded

	after the last water quality sampling trip on January 24, 1989.

	The South Fork station, with a drainage area of 38.4 square

	miles, measured virtually all flow from the South Fork of the 

	river. Carlton Branch, with a drainage area of 7.9 miles,

	measured flow from a small sub-basin dominated by agriculture.

	The Dug Creek site, with a drainage area of 3.6 square miles,

	measured flow from a very small basin with mixed land use.

		The rainfall data collection network for the study included

	five stations in the existing District network (Figure 4.1).

	Periods of record for these stations range from eight years

	(Wimauma - 1981) to thirty-four years (Fort Green- 1955).  An 

	additional station at the FP&L power plant was established to 

	measure rainfall inthe southwestern portion of the drainage

	basin. Daily rainfall records were available from all the 

	stations during the study year.  At two of these stations

	(Wimauma and FP&L), recording rain gages make the examination of 

	hourly rainfall data for the study year possible.


							34




RAINFALL

	Monthly and total yearly rainfall amounts for the six

stations in the project area are listed in Table 4.1.  Total

yearly rainfall for these stations averaged 52.6 inches, which is

near normal for the region.  The yearly total of 46.6 inches for

the FP&L station in the southwestern are was somewhat lower than

totals for the other five stations which ranged from 51.2 to 56.5

inches.

	Seasonal rainfall distribution in the basin during the study

period found the spring dry season and the summer rainy season to

both be somewhat exaggerated.  A comprison of the bar chart of

average monthly flows for Ruskin (Figure 2.2) and the monthly

values presented in Table 4.1 shows that rainfall was near normal

at most of the stations from January through April, with a sharp

drop in rainfall occurring in late March at the beginning of the

dry season.  This transition can be seen in greater detail in

Figure 4.2, where daily rainfall amounts during the study year

are shown for three of the stations (Ruskin, Fort Lonesome,

FP&L).  Rainfall from mid-March to early June was particularly

low, with only 2 or 3 rainfall events of over 0.2 inches

occurring in the basin.  When the summer rains began in June they

were well below normal for the remainder of the month at four of

the six rainfall stations.  As a  result, from late March through

June the basin experienced a pronounced dry season during which

rainfall was below normal.

---------------------------------------------------------------------

					35







                
 











                        Table 4. 1.                       Monthly and total                          yearly rainfall (inches) at
                                                           stations shown in Fiqure 4.1 durinq January 1938
                                                          to January 19B9.                           Listed yearly totals are for
                                                           1989 only.



                                                                                Rainfall (Inches)


                                                            Ft.              FIDUr                 Ft .
                        Da t e         F F-'?! L           13 r c;? c? n    1-: r n     r s      L-gneg-c-me Ruskin                       L) i M @:k U fn k
                        1/8S
                                                                                                                                                        F,


                        X2,                                                                                                                           C)


                        1131    8             3. a                                    5.4                  3. 6               5 . 1               4.4                    4.B
                                                                  6.


                        4/80
                                                                 1.7                C). 4                 1.7                21 . I                                      I . E,


                        5/ae                                      1. C)               1.2                  C). 8              1. E.


                        G/eB                   1.8               1.8                      j               4.8                2.B                1.9                            1


                        7/38                  33 . 7           1C). 4                 6.7                 10. 9               G . 7                                      7.4


                        B/Be                 9. B             15 . 2,             10. 5                                      9.8                9. E.                 10. 0


                        9/88                13 . F,             10 .                  9.4                 13 . G-            I                                         j--:,. -7


                        10/88                1 . 0              0. a                C). e                 1.4                0.
                                                                                                                                                1.5                      1.


                        11/88                  3.5                                                                1


                        12, /1 E., S         I . 1                                       ej               C).7               0.9                C). 'D


                                                                                                                                                  1 . G





                        TOTAL             -4 E-, . E.         5 F, . -5                                                                      51 1, . 15                  52'.' . E,



                        ---------------------------------------------------------------




                                         RAINFALL AT FT.. LONESOME

                         4.5



                           4












                         2.5-
                  LU


                           2-











                                    J   F                  J        A                  0    J




                                              RAI N FALL AT     RUSKIN.




                         2.6-


                         2.4-


                         2.2-


                           2


                         1.8


                         1.6


                         1.4


                         1.2




                         0.8


                         0.6


                         0.4


                        .0.2
                           0        LL
                              B    J    F    M    A   M    J    J   A    S    0    N   D    J
               Figure 4.2.     Daily rainfall  at three stations in or near the Little Maxiatee
                               River basin from December 1987 through January 1989.











                                       RAINFALL AT FP&L









          Ln
          w
          5       2-
          Z












                0.5-




                      J    F    M    A    M


















        Figure 4.2.     (Continued)





	In contrast to the prolonged dry season, rainfall was

abundant in the late summer.  Rainfall totals were near normal

for July and above normal for August and September.  Of

particular significance were a three-inch rainfall that occurred

in early August and a four-day rainfall event in early September

when a stalled frontal system dumped over ten inches of rain in

the basin.  Rainfall was greatly reduced in late September,

however, and October received below normal amounts.  The passage

of two frontal systems in November resulted in a basin average of

4.4 inches for the month.  During December and early January

rainfall was again low, but another winter front in late January

caused two days of rain at the end of the study period.

	In sum, total rainfall during the study year was near normal

but showed extreme fluctuations in short-term and seasonal

quantities, which is not unusual for west-central Florida.  With

regard to the water quality aspect of the project, this pattern

was fortuitous for it allowed monitoring of the basin under a

wide range of hydrologic conditions.


STREAMFLOW

	Streamflow measured at the six stream gaging sites shown in

Figure 4.1 closely followed the seasonal rainfall pattern

described above.  Average monthly flows and average flows for the

study period for the six streamflow sites are listed in Table

4.2, while hydrographs of daily flows for these same stations.

are shown in Figure 4.3.


					39

 


















                   - - - - - - - - --- - - - -7 -- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                   TableO4.2.                  Average monthly and study peric-,d streafriflc-w (cfs)
                                                at stream gaging sites shown in Figure 4.1 during
                                                January i9se to January 1989.




                                       LMR                      u t h              LMR                  r I t ---, 1-1 C                  DLkg
                                                                                                                        .Ypr ess
                   Da t e            W i rri.-I U M @-I    F*,---,I'[:: Ft. L..--tnes17ifTjPI       Dr anc h            C: r e c--? k  C, Y. p e k


                                                       2-7.
                   1/ple            I 121. ID                               1 E3. 1                   8.6               3.7


                      8 EI        140. 1                                                            D. 7             1 C). '-D


                   3/88                                G     3,             4.7.8                  1 FI.              1 19. 5


                   4 / BE             I              1 '3'. 4               11.4                    -:4
                                                                                                                        1.4


                   5/88              50.2,             12.6                                          6. ID                   7            1.7


                   6/88             @_j . 4            9.5                                              5               1 . 0             0. 5


                   7 / 39           1       1          40.                  4S. 0


                                                                                                  2C . G             13 1 . 1             7.8
                   S/BE3          3 7 -2 . '-2-    1 '2"j . 7            10 '3 . E,


                   9/ae          1120. 1            33 * 225 . 9 3       254. 'D                    59.4              89. 4


                   1 0//BB        1 '@ -2-5 . 4        .4. 3                i'71. 9               1     8               3. 0


                                                                                                                             -7,
                   11/38            1339. 4            4 0 . 3-1                                   :2,C). 4              j                7.1


                   12/88            I-=@9. 0                 E,             10. 1                  11.5                                       -71


                   1 /G-D           1       4

                   -----------------------------------------------------------------                                                      @-7
                   Ave.-                    7          E-1. 4               4G.    '7,              15.


                   --------------------------------                              --------------------------------












                                                             bUU I H f  ILPM Nt:HK WIMAUMA DISCHRRGE

                                        '4200


                                        4000


                                        3800


                                        3600


                                        3400





                                    L)
                                    -   1200
                                    U.)
                                    0
                                    W   1000


                                        goo
                                    in

                                        GOO


                                        400


                                        EDO


                                        a

                                                 JAN   FEE    nAR   APR    nRy   JUN    JUL   RUC   SrP    OCT   NOV    DEC   JRH

                                                                             JAN. 8B - JAN. 89





                                                    CYPRESS CREEK NEAR WIMRUMR DISCHRRGE

                                                                                                       RVII MR

                                       STT



                                       8t5

                                       goo

                                       375

                                    LL too
                                    t  -

                                    W
                                       130

                                       in

                                       100

                                    0  T3








                                             JAN    FCR    nAR    APR   nAY    JUN    JUL   AUC    SEP    OC7   may    DEC    JAN

                                                                          JAN. 88      JRH. 83





                     Figure 4.3.             Hydrographs of daily streamflov at the stream gaging sites shown
                                             in Figure 4.1 for the period January 1988 to January 1989.















                                                                           FLOW NEAR XIMAUMA













                                        Otto  -

                                        Soto  -


                                        1900

                                        1600
                                  cc
                                        14130
                                  u
                                        iftoo

                                        3600

                                        ROD




                                        too



                                                  DEC     JAN     rEl     hRR    APR     MAY            JUL     uC     SEP    DO             DEC    in"


                                                                                  DEC. Be       JAN. 89









                                                                LT. MANATEE NEAR FT-LONESOME
                               2100

                               ZDCO

                               1900

                               1800

                               1700


                         u       Soo
                         ui      Soo
                                 700   -
                         C=
                                 Soo   -
                         L)
                         U)      Soo   -

                                 400   -

                                 300   -

                                 200   -

                                 100

                                 0

                                           DEC    JAN    FES     MAR     RPR    MAIY    JUN    JUL     RUG    SEP    OCT     NOV    DEC    JAN

                                                                          DEC. 88             JRN.       SS



                  Fizure 4.3..                (Continued)
                                                                                                               LIJ@








                                                                         CARLTON BRANCH DISCHARGE


                                                  475




                                                  450




                                                  425
                                          U)
                                          LL
                                          U


                                          Ld
                                          LD
                                          x       150 -
                                          cr-

                                          L-)
                                                  100 -




                                                  50 -






                                                                 J8H    FES MRR AFR MRY JUN JUL RUG                        SEP OCT       HOY OEC JMH

                                                                                     JRN. 88                    JRN. 89.



                                                                                       DUG CREEK DISCHARGE


                                               g"















                                               Irs
                                          Ix


                                               Im








                                               rz




                                                                rts     MO      VVR     MOT     AW              "M              OCT     WV     IMC     4OX




                               Figure 4.3.                      (Continued)






	A comparison of average flows for the study period gives a

grouping of the stations that correspons to their ranking based

on drainage basin sizes.  The Wimauma site had by far the highest

average flow at 209.7 cfs, which is approximately 22 percent

greater than the long-term average for this site.  The South Fork

and Fort Lonesome sites, with average flows of 61.4 and 46.2 cfs,\

comprise a middle group with intermediate drainage basin sizes

(38.4 and 31.4 square miles, respectively).  The average study

period flow for the Fort Lonesome site was 56 percent greater

than the long-term average flow for this site, which is based on

25 years of record.  This period of record, however, has been

characterized by a trend in below average rainfall.

	Average study period flows for Carlton Branch and Cypress

Creek were nearly equal (15.5 and 15.9 cfs, respectively)

refecting their nearly equal drainage basin sizes (7.9 and 8.1

square miles).  The small 3.6 square mile basin corresponding to

the Dug Creek gage yielded the smalles average flow (5.6 cfs)

for the study period.

	A comparison of the hydrographs of daily streamflow values

(Figures 4.3) with the plot of daily rainfall amounts (Figure

4.2) indicates close correlation between these two variables.

Rainfall events in January, February, and March resulted in

moderate flows for all the streamflow sites.  Declining flows

from April through June occurred with small peaks in flow

observed after brief rainfall events.  Rainfall was somewhat

variable in the basin during July (Table 4.1) with amounts over

				44








 

~0







                   t~en i n~ch~e~c~E f ~a~ql I i n~g J~i~, ~n the ~P~ql~ast~ern part -~.-~,f t~qhe             r  n~,~-~-~. u n ~c e

                   r~-~,~,~-~- Y~- e a. ~s~i~@ ~e ~-~-~@ ~qi n ~s t ~i - ~e a fr~i f 1 ---1 ~w ~w ~e ~r ~e.~-~@ ~o ~qb ~s~@~, ~e r v ~e d i n J~U I ~qyt a. ~q1. 1 ~c~-~-: t: ~'~E~., t i ~:.~, n

                   except Dug and Cypress Creeks i~n t~qhe n~c~-rth~-~-~centr~al part ~-~-~,f the

                   basin where rainfall w~a~s lower.           All stations ~E.~-~@xhib~qited high


                   ~      ~qow~s                         ~-~id  ~arti~c~qu~qlarly in early Se~ql~-~-~itember, when
                   ~924;56;124qin early A~U~QU~qSt ~a~i        p~@

                   ~M~1~,~RX~qiMUM flc~ws~, were observed                stations.     The peak fl~,~nw of

                   ~,~qD7~qF~q3C) ~cf~s at t~qhe Wim~aum~a station was over 5~q0 times greater than

                   the ~aver~ac~i~qe flow for this site a~nd c~c~-rresp~.~:~,nd~(-~=?d to a 1~q0- to ~'2~q5-

                   year fl~-~-~-~I~,~-~-~-d event. Alth~C~-U~Qh ~!~-~-~,~o~qm~e homes ~a~nd ~cther strU~Cture~s were

                   inundated during this September flood, ec~onc~,mic damages ~qin t~qh~e

                   basin were min~--~-r d~ue to the undeveloped character of the river

                   corridor.    For the remainder of t~qhe study period, fl~ow~S at all

                   sites returned to low to moderate levels with brief pea~ql~.~-~-s

                   C~ICCLA~I~-~1~-ing during November and January ~in response tc~-~, rainfall

                   associated with the pas~qsa~qq~L~- of ~-:~-~-~-~-~qld fronts.

                        One interesting p lien omen ~-~-~,n t~qhat was observed during t~qh~e

                   study w~as a. ~c~qle~ar~.d~qifferen~ce in b~qase~2p~1p~1p~ levels between the ~S~ub

                   basi n~s~.  For instance~, t~ql~-~ie.~- ~qF~'~.~-~-~,rt Lonesome gage measures flow fr~o~a~l

                   an area ~a1m~c~ist f~I~DUr times greater than t~qhe                      Branch site.

                   D~Uri~n~qg wet months, average m~c~-~,r~ith~ql~qy flows ~z~-~ct: F~,~-~-~~,r~,~qt L~one~s~c~.~,ME~? ~k~k~)2~r~e

                ~q-significantly greater than at the                        Branch site.      F r t I ~-~j ~e

                   dry m~c~.~,nth~s~. ~r..April, May, June, ~qO~,~:tc~,bE~-~.~,~r, and December~q), h~c~-~'W~qev~E~--~r,

                   ~qav~qer~qa~qc~qie flows at Fort L~qone~q'~q@~q,~q:~q,~qome ~qand                 ~6qB~qr~qan~qc~q-h were nearly


                   eC~6qjU~qE~qkI  These ~qY~q'~qE~qS~qL~qAIt~qS and the water chemistry data ~2qr~q-~q-~q)r~qe~q-~qs~qe~qnt~qed in

                   ~qI-~6qI~qi~qapt~qe~qr V indi~qc~qa~ql~ql~q.~q-~q-~qe~q- that dry            flows i~qn ~0qC~q,~q-~q-~qirlt~8qon Branch~q; are





                                                            4
 




heavily supplement by runoff from farms which originate as

pumpage from groundwater sources.

TIDES

	Water levels in the lower fifteen miles of the Little

Manatee River are affected by tidal fluctuations in Tampa Bay.

At the most upstream extent, this effect is very small and

restricted to periods of extremely high tides in the bay.  Water

levels at the mouth of the river are largely controlled by tidal

fluctions in the bay, but periodically can be significantly

affected by high river flows.

	The recording of tide stage during the study is very

important for interpreting the estuarine water chemistry and

salinity results.  Therefore, a water level recorder was

installed at the mouth of the river at Shell Point and operated

by the USGS for the duration of the study.  This instrument

recorded water level measurements every 15 minutes with retrieval

of these measurements plus daily mean, minimum, and maximum

values possible.

	Tides at the mouth of the Little Manatee River contain a 

mixture of diurnal and semi-diurnal components.  On most days,

there are two high and two low tides.  The high tides are of

unequal height consisting of a high-high and a low-high tide.

Low tides are similarly of unequal heights.  During some periods

of the year, depending on astronomical forces, there is only one

high and one low tide daily at the mouth of the river.  Water

					46





 



levels and tidal fluctuations in the lower Little Manatee River

can also be affected by the action of prevailing winds on the

waters of Tampa Bay.

	Based on data collected between January 1988 and January

1989, the average daily tidal range at the mouth of the Little

Manatee River was 2.47 feet.  Average monthly valuesl for daily

mean tide, daily maximum, daily minimum, plus the absolute

maximum and minimum tides for each month are illustrated in

Figure 4.4.  Monthly mean water levels were highest in the fall

(September through November), but the September value was

affected by the extremely high river stages during the flood in

the early part of the month.  The differences between monthly

values for average daily maximum tide and average daily minimum

tide range only from 2.25 to 2.60 feet, demonstrating the small

seasonal fluctuations in daily tidal ranges at this station.














				47

                
 








            Figure 4.4.        Average monthly values for daily mean tide, da             'ily minimum and
                               maxi-n- tide plus monthly maxim= and minimum tide at the mouth
                               of the Little Manatee River from January 1988 to January 1989.



                +4.0-


                +3.5-


                +3.0-
                +2.5-                                                                            Maximum
                +2.0-
                                                                          7z
                                                                                                 A verage Daily
                +1.5 -                                                                           Maxinium

                +1.0-
                                        X@z
          >
          z     +0.5--                                                                           Mean
          LU
                   0 -
          LU
          LL
                -o.5

                                                                                                  iverage Daily
                                                                                                 minimum



                                                                                             --- Minimum
                -2.0


                -2.5


                -3.0
                              F M A M J                   J    A     S. 0 N          D     J

                                                      MONTH












V.   FRESH WATER CHEMISTRY





OBJECTIVES

	The water chemistry program had three objectives:

	1) to determine the flux of nutrients and suspended solids

	    contributed by each of the sub-basins of the Little

	    Manatee Watershed,

	2) to determine seasonal variations in concentrations of

	    these substances in each sub-basin,

	3) to evaluate the movement of these materials through the

	    Little Manatee estuary.


	The first two objectives required an examination of water

quality in the freshwater streams of the basin.  Water quality

data will be compared to land use and soils in the respective

sub-basins to document the effects of various land uses on water

quality.  The third objective is addressed in the following

chapter on Estuarine Water Chemistry.


SAMPLING AND ANALYTICAL METHODS

	This report on stream water quality is based primarily on

data collected between January 1988 and January 1989.  During the

study year, water chemistry and physical parameters were measured

at seven freshwater stations in the Little Manatee basin (Figure

5.1).  Six of these stations were located at USGS stream gaging

sites, while the seventh station was located at a site on the

				49
       
 









            Little Manatee River Freshwater
            Station Locations





                                                                                             r
                                                               Ilk
                                                                                        E      .7    GorN
                                                     "S
                                                                   A
                                                                Az                                                          4

                                                                                                                                It
                                                             F           C
                                                                  2                                                                              U.,







                          Bi-Weekly sampling stations

                          May and September sampling stations
                      Figure         Locations Of freshwater stream sampling stations in the Little Manatee River basin.






                Figure 5.1.     (Key)



                                                  A,
                                                  i ,
                1.    Bi-weekly sampling stations and continuous USGS streamflow gaging sites
                      A.   Dug Creek
                      B.   Cypress Creek
                      C.   LMR (North Fork)

                      D.   South Fork

                      E.   Carlton Branch

                      F.   LMR near Wimauma

                      G.   LMR near Ft. Lonesome




                2.1   May 17, and September 21, 1988 dissolved constituents sampling
                      1.,  Dug Creek at Saffold Road

                      2.   South Fork at Bunker Hill Road
                      3.   Alderman Creek at S.R. 39

                      4.   Alderman Creek at Taylor-Gill Road
                      5.   Howard Prairie Branch at Grange Hall Road

                      6.   Pierce Branch at Owens Road

                      7.   Pierce Branch at C.R. 674
                      8.   LMR Grange Hall Road
                      9.   Carlton Branch at Sweet Loop Road
                      10.  Carlton Branc h at Colden Loop Road

                      11.  Unnamed Creek near U.S. 301

                      12.  Unnamed Creek near railroad bridge

                      13.  LMR near FP&L intake

                      14.  Unnamed Creek near C.R. 579

                      15.  Gully Branch
                      16.  LMR main channel above Gully Branch

                      17.  Carlton Branch at confluence with-J..MR




river ("C", North Fork) where streamflow can be estimated by

station differences.  Sampling at these stations was done

approximately every two weeks, so 26 regular samples were

collected during the study year.  At each stream sampling

station, duplicate water samples were taken at .5 m depth or at

mid-depth if total depth was less than one meter.  Filtration for

separation of particulate (C, N, P) and dissolved nutrients (PO4,

NO  $ NO  Organic Carbon) was done in the field with filters and

filtrates kept in iced coolers for transport.  Water samples for

chlorophyll analysis were kept chilled and transported to the

Department of Natural Resources Laboratory in St. Petersburg

where filtration for pigment removal was done the same afternoon.

Samples (filters) for particulate phosphorus determinations were

periodically shipped to Savannah Laboratories and Environmental

Services, Inc. (SL&ES) in Savannah, Georgia where digestion and

measurement was done.  Remaining water chemistry parameters were

determined at the District Laboratory in Brooksville.  Parameters

measured and the analytical methods employed are listed in Table

5.1. Also, at each sampling station, in situ measurements of

temperature, dissolved oxygen, pH, and specific conductance were

made with a Hydrolab meter at .5 m or mid-depth, depending on

water depth.

	At the same stations as the bi-weekly sampling, major ion
						   _
species (Ca, Mg, K, Na, Fl, Cl, and HCO  were measured on

duplicate samples on a monthly basis for a total of twelve

regular sampling events.  In addition to regular bi-weekly and


				52









 








                                 Tab I e 5. 1.                     Water qualit@ parameters measured and analytical
                                                                    methods for freshwater and estuarine sampling
                                                                    stations during January 199B tc, January 19B9.

                                 -----------------------------------------------------------------


                                 Pa r a m P t e r                     Un i t s,                         Method                             F, c-., f P r E., n,-- c-D


                                 Temper at t..tr e                                                 Hydr,---11 ab                             Hydrolab InstrUments'.

                                 Sp E-C i f i C                    Um Fic-, s / c m               Fly   drolab                             Hyclrolab lnstl@Uments
                                     n d Li :: i, a nc e


                                 pH (field)                             P H U n i t s             Hyd r c, 1. ab                           Hydrolab InstrUments

                                 Dissolved                                  mg/1                   Hydrc.lab                                 Fiydrc-lab Instruments
                                 Oxygen

                                 TUrbidity                                    NTLJ                  Nep h e lcimet r ic                                         APHA, I9P)

                                   1:1 1 Cir                                                          Nessler tubes                                             APHA, 19B5
                                                                               FICU


                                 Total Suspended                            mg/l                f iItrati----n/qr.-xvirTietric                                  APHA, 19 e!.:,
                                 Sol i ds


                                 TSS-vc-I at i I e                          mg/I                  Qr avi met r i c / i cin i t i on                             APHA, 1965-1
                                 f r ac t i on


                                 Part j. c ul. at e                         mg / 1.                         C-H-N analyzer                                      Per k i n -E I mer
                                   ar b on                                                                                                                      I n st r umen t


                                 Par t j. C U 1 at e                        mg/I                            C-H-N analyzer                                      Fer 1.;-. i n-E I mer
                                 nitroaLr-n                                                                                                                     InstrUments


                                 Particulate                                mg./I                         acid diqe=-tii--In/                                   EPA,
                                   phosphorOUS                                                               colorimetric                                       APHA,         19 8 5

                                                                            mg/I                                     -rime -ir                                       -IA,        -)C5
                                                                                                                    C          tI


                                 N 0     NI 0                               m C1 /                               1. c, r i m e. t r i 1z                        A. P         i :D e5


                                 PO                                         MI Q / I                             o I or i rrEt r i c
                                                                                                                                                                APHA,

                                 Si 1 ir a                                      / 1                           crD 1,--ir i met r j.;--                          APHA,        I 'D B 5



                                 -----------------------------------------------------------------

















                                      C. rI t- n u


                 ------------------------------------------------------------------


                 Par amet er                Uni ts                   M e t h ---- d           R e f e r e nc e



                                                                    C,
                 C: h I C, r C, p 11 y I I a    rn g / ril           p e c t r   h Cl   fri E- t Y. i      APHA, I., Pff5


                 *CZII. C i UM                  mg / 1               Atomic Absorption                     APHA,     19 C -5


                 *Magnesi UM                    mg/l                  Atomic Absorption                    APHA, 1-985


                  Po t .1 S 5 i LA (TII         fnq                  Atomic Absorption                     APHA, 1985


                 *Sc,dium                       mg/l                  Atomic Absorption                    APHA, 1985


                 *Sulfate                       mg/l                    tUrbiclimetric                      APHA, 19B5


                 *Ch lor i d e                  mg/l                       titration                       APHA, 1,D e,,j



                                                                                                           APHA, 192C7
                 *F1 uor i de                   mg/I                      el ec t r ode


                 *Ali-.-alinity                 (nQ/l                      t i t r at ion                  APHA, 1985


                    Fresh wz:tter stations only

                 -----------------------------------------------------------------












   		monthly sampling, two additional sampling trips on May 17, 1988

		and September 21, 1988 were performed when major ions, dissolved
		
		nutrients and physical parameters were measured at an additional

		17 water quality stations (Figure 5.1).  Duplicate samples were
		
		not collected during these two additional sampling events except
	
		for duplicate analyses performed as routine quality assurance.


            OTHER DATA SOURCES

			Other surface water quality data for the Little Manatee

            River basin are available from the U. S. Geological Survey (USGS)

		and the Hillsborough Environmental Protection Commission (HEPC) .

            Mean values for several parameters measured by these two agencies

            during 1986 to 1988 are listed in Table 5.2.  Station locations,

            for these data are the same as three of the stations, shown in

            Figure 5.1 and follow the same nomenclature.
 











                   Table 5.2@'. Mean values for selected water chemistry parameters in
                                                 the Little Manatee River Basin recorded by the
                                                Hillsborough County Environmental Protection Commission,
                                                 1986 and 1987.                        Mean values recorded for Ft. Lonesome by
                                               the USGS during 19B6 to 19BB are also shown.


                                                                                  LMR near                                  LMR                         LMR near
                   F'arameter                              Un j. t s             W i m EA U m a                                   F,-.,rl::*)          F t: . L -:-, n P siri m cn
                                                                                                                                                      ('HEF,i--,*) (USGS)


                                                                                                                           "@I -7 1
                   Spec i f ic                          U M h 0 S       M                  @15                                                                               137
                   C:,::,ndUCtance


                   pH                                 pH Units                           7.5                               7.4                          7.4                G.e

                   Turbidity                                 NTU                               8                                  7                           -1


                   Col,or                                  PCU                             58                                65                           e.-.,                 9


                   Organic nitrogen                          mQ/1                          .96                               .9C)                     1 . OF,                aG

                   NH        (as      N                    mg/1                            i G                                                             10              ---

                   NO &-NO -z         (as N)               fTIQ / 1                      .57                                 --                         .13                  10

                   Total Phosphc-rus                       mg/l                          .4.5                              .55                            E-0              .54

                   Chlorophyll a                           mg/m                            --                             -12'. 7                      1. C)                 --

                   Ca. I C i U M                           mg/I                            26                                                              17                14

                   Sul f at C='                              mg/1                          12, a





                   DATA REDUCTION


                                   The T--!,-ita @,.jere fira-A-- c-.'-,---I-smined 41- c                       a       e r t C-tin similciritieE@ and


                        differences in water quality am,--,ng stations and seas,:,ns.                                                                              A 11

                        statistical anaIysE-.,s and                                                                  --,f bi-weekly dat.1 in thi5

                                                                                                                                          les.          T@),-E?n, the
                        report are based on thtlE? me,-=knE of dUPIi,:E-ktL-                                                           P --

                        CIE-kta k4e)-E' C--V@@klU&'L-E'd t,-' CIPtermine the relativE-., imp-r-11-ance cif

                        flu.,,,es                                        (J)Utriants and                                          fr,::,m the maj----r


                        S, U b  b Zk S i n. si.     f t. I--, e L      t 41--IE-!




Branch, South Prong, Dug Creek, Cypress Creek, adn Wimauma) and to

elucidate processes influencing the transport of thesr materials

through the Little Manatee estuary.


Estimates of Annual Material Flux from Sub-Basins

	The sum of the discharges recorded at the Cypress Creek

(CYPR) and Wimauma (WIMA) gaging stations represent the

approximate total fresh water and material fluxes to the Little

Manatee estuary.  Thus they, along with Tampa Bay, are the major

sources of materials, such as nutrients, supplied to the esturary.

	For the purpose of evaluating the relative importance of 

each sub-basin, the discharges and fluxes determined from data

collected at the Cypress Creek, Dug Creek, Carlton Branch, Ft.

Lonesome and South Prong gaging stations are assumed to represent

the transports from their respective watersheds.  The discharge

and flux determined from the data collected at the Wimauma gaging

station represents the influence of the intervening watershed

below the upper sub-basins (all except Cypress Creek) when the

sum of the fluxes and discharges from these are subtracted.  This

part of the watershed is referred to as the Inner sub-basin (IB).

	The flux or load of a chemical substance transported from

each sub-basin is simply the product of the chemical

concentration and water discharge observed at the gaging station.

Instantaneous  values of flux are relatively simple to derive for


					57










 



each gaging station using measured substance concentrations and

instantaneous or daily mean discharge at the time of sampling.

It is, however, much more difficult to estimate, with a high

degree of accuracy, fluxes over longer periods of time such as a

year or more since this requires long term records of

concentration (C) and discharge (Q), so that flux (F) can be

calculated by intergration using the equation:



			F =		_ *C Qdt					(1)


 It would still be easy to calculate fluxes if concentrations of

substances were constant over all variations in discharge.  This,

however, is not the case since the concentrations of virtually

all substances, both particulate and soluble, vary with

discharge.  Nonetheless, several approaches have been used to

calculate fluxes with limited data collected over various flow

conditions of a watershed.  Generally the approaches used involve

either extrapolation or interpolation of the data.  Both

approaches were used in this study and are discussed below.

	Extrapolation method for estimating material flux.  These

procedures attempt to extrapolate the available database by

developing rating relationships which link chemical

concentrations measured at infrequent intervals to river

discharge at the time of sampling.  Rating relationships are

normally developed for sites with discharge monitorying facilities


				58











 




so that the rating function may be applied to a continuous flow

record thus allowing for extrapolation of chemical concentration

(and flux) between periods of sample collection.  Simple power

functions of the form:


			Concentration = aQ						(2)


are used to relate the concentration of a substance and river

flow, Q.  Such relationships have been routinely documented by

many studies.  For example, suspended sediments generally show

increased concentration with discharge following a relationship

similar to the described in equation (2) with b being a positive

number.  In the case of total dissolved solids a similar

relationship is observed,  but b is often negative (Figure 5.2).

Rating relationships or rating curves have been demonstrated for

many specific substances, for both natural and anthropogenically

disturbed (e.g., agricultural areas) watersheds (Nilsson, 1971;

Turvey, 1975; Walling and Webb, 1983; Walling and Kane, 1984).

	Although rating relationships for total dissolved solids

often exhibit decreasing concentrations with increasing

discharge, specific dissolved substances such as nutrients often

show increases with discharge (Walling and Webb, 1984; Webb and

Walling, 1985).

	Rating curves are developed by obtaining concentration data

over seasonal variations in discharge for a given watershed.

Fitting concentration data to discharge is usually accomplished

					59
















 



by least-squared regression techniques.  This approach was

employed in this study using the individual bimonthly

concentrations of constituents and mean discharge for the station

on the day of sample collection using a log transformation of

equation (2).

	Other authors (e.g., Jansson, 1985) have argued that other

methods of curve fitting are more appropriate, and in some cases

(e.g., Hall, 1970; Davis and Zobrist, 1978; Foster, 1980), the

relationship between concentrations and discharge will not be

described by a simple power function.  Nonetheless, we felt that

the approach used in this study was more appropriate given the

limited data set for each station.

	Many investigatiors have stressed the complexity and

variability of storm-period sediment and solute responses to

discharge (Walling and Foster, 1978; Miller and Drever, 1977;

Foster, 1978a,b; Reid et al., 1981; Dupraz et al., 1982; Webb and

Walling, 1983; Walling and Webb 1986a,b).  Thus it is important

to determine concentration relationships to storm related

variations in flow.  In practice, for a given watershed, separate

rating curves are developed for seasonal flow and storm related

flow.  For this study data collected during storm event campaigns

are related to discharge averaged over hourly intervals also

using the least squares regression approach.






				60





 




	Once the rating curves were developed annual flux of a given

material by each river was calculated using the following

equation,
					  _n_					
			Flux = E 	aQ     t				(3)
				i = 1

where Q, is the mean daily (hourly from storm event) discharge

recorded at the specific stream gage, n = 365 (or the number of

15 minute intervals represented by the storm event), a and b are

constants derived from the least square regression analysis of

concentration on discharge, and t is the time over which Q, is 

averaged.

	Interpolation method for estimating material flux.  Several

interpolation procedures have been used for estimating total

loads or fluxes of materials.  Five representative numerical

procedures are listed in Table 5.3.  These procedures make the

assumption that the chemical concentration of a water sample is

representative of conditions in the river for the period between

sampling.  These approaches essentially attempt to weight the

concentration to discharge. Because of the sometimes

considerable differences in flux values generated by the

different procedures, two were used:  Methods 3 and 5.  In each

case the calculations were carried out using the results from the

26 weekly samples collected between January 1988 and February

1989.  Thus n = 26 and the conversion factor K was adjusted for a

discharge record of 13 months.


						61










 










           Aable 5.3. Interpolation methods for flux calculations.





                        WelhDd                                     Numerical Procedure


                                                                              n      n
                                                                              r-     7-
                                                              Total Load wK      n

                                                                                   n
                                                                                   7-
                          2                                     'Total Load  KQr
                                                                                     n



                                                                                n
                          3                                      1 otal Load - K 7
                                                                                    rk



                                                                               n
                          4                                     Total Load  K2@ (3i0p)

                                                                             n
                                                                           KY, (CiOp)
                          5                                   Total Load        n      Cr

                                                                               gal




                          K = Conversion Fa--tor To Take Acrount Of Period Of Record
                          Ci =   Instantaneous Con--enlration Asso--i ated With Individual Samples
                          Oi =   Instantaneous Discharpe At -5me CY, S=)lino
                          Or =   Mean Disch,aroe For Period Of Rec:ord
                          C      Mean Disc;haroe For Imerval BeTween Samples
                          n      Number a, Sam,D:!es





RESULTS

Water Quality Characteristics

	Hydrographs and chemographs for the six gaging stations

during the period of study are shown in Figures 5.2, A through F.

Dates of routine sample collection are indicated by data points

along the time axis.  Time is in days starting with 1 January

1988.  Compared to historical streamflow data, the sampling

appeared to capture a fairly wide range of discharge conditions.

	The base flow recorded at all gaging stations is quite low.

Superimposed on this pattern are short period storm spikes.  Only

one storm event, occurring during September, appears particularly

significant.

	Bi-weekly water quality sampling during the study year found

pronounced differences in water chemistry between the seven

stram stations.  DOC and nitrate concentrations were highly

variable during the study period.  Concentrations of ammonia and

phosphate were somewhat less variable and reached maximum values

between July and September, although this varied between 

sub-basins.  This was the approximate time of the highest

discharge.

	Particulate carbon, nitrogen and phosphorus vary, in

general, with total suspended solids.  The maximum or spike in

particulate substance for the Cypress Creek, Carlton Creek,




					63










 








                                Hydrograph and Chemographs for Ft. Lonesome Gauging Station


                                                                                                                                       kv
          00                                       0a                                       4
          Do    FLOW                                      NH3                                      PC

          ,do                                      CA

          so                                                                                2

          20                                       02

          10
            0                 L                    00                                        0
            a   00  100 U10 2M 200 SM 000  400        a  co too iao aw wo wo aw Am            a  ao  go Ido 200 2w am Wo 4w



                                                   oil
          oo   D3. C                                     PO4                                      PN
          26                                       ad
                                                                                            02
          20

          Is                                       04

          to
                                                   02


                                                   00                                       00
            0   80  100 SW ZO  200 400 000 4CO
                                                      a  no 100             wo aw   400       0   00 too 100 aw am 000   wo 400


          04                                                                                CA
          04                                                                                      Pp

          ob
                                                                                            02

          062

          at                                                                                at
                 L










          00
                                                      0                                     00
            a   go  100 140 2w ka am       4w         0      10,0 100 .200. 200 moo ow 4w     0   00 IW M 200 2M WO OM 400








                      Hydrograph and Chemographs for Carlton Branch Station






       so                       06                          4
         FLOW                       NH3                         PC

                                OA


       10


                                02




       0                        00                          0
       0 so IM IM wo aim M 4co   a  no 100 lao am no Sao am 4w0no 100 wo 2w am am 400



       so                       08
     .u DOC                         PO4                                      pN
                                as                          04
       so


                                C64                         U


       to
                                02                          ell



                                CIO
       0so jC0 mo wo am M  4w    a  so wo iao Sao 2w wo sw 4w0 so ica Mo sw Sao ow am 4w


                                20                         0M
         NO                                                ow  pp
                                is

                                                           am
       go
                                10
       u                                                   Q10
       w                                                   ow
       a&                                                     V-4@
       Go                                                  000
                                 t
































       a so %a mo Sao M am no 4w a Go 100 lao wo no Sao M 400 0 w   V0   M M w 4w







                                         flydrograph"and Chemographs for Dug Creek Station



                                                                                              12
                   FLOW                                     NH3                                    PC

                                                    064
             4                                                                                a

             2                                      02




                                                    010                                       0
              a   00  IDD U10 200 200 800 OW 4M        a  no  SOD lao 201) aw am am 4w         0  00 100 IBO 200 200 9M BM  400

             20                                     06                                        as
                                     DOC                  PO 4                                    PN
             16                                                                               0B
                                                    OA
                                                                                                                                     LD
                                                                                                                                     LD
             10                                                                               cw

                                                    02

                                                                                              CL2

             0                                      00                                        00
              0   00  100 MO 200 2W boo Sao 4w         0  40  100 100 2W ftO MW OW 400         0  00 Im 100 Sao 200 moo No 4w

             4                                      415
                  NO3                                                                             Pp

                                                    so




                                                                                            000-


                                                                                            000-


                                                                                            ow
              0   so 100 lao am 200 9M IW 400          0  00 wo 100  sm 900 sw sw 4w             w IM w wo wo           w   IKM
                                                                                                                 L


                            A







                                    Hydrograph and Chemographs for South     Prong Station




                                                  Da
                FLOW                                     NH3                                    PC
          90
                                                  W                                        2


          00


                                                  02
          so



          0                                       00                                        L  I-
             a w                  sw m   4w        0   00 IM 100 SM 200 OW OM 400           0  na wo Ina 2oo 2w  am ano  4cc



          so                                      Do                                     025
          so   DOC                                     P4                                020   PN
                                                  00
          20
                                                                                         ala

                                                  C64
                                                                                         010
          to
                                                  C12                                    006
          &                                                                              am i             @
             0 00  100 UQ 200 200 SM 800  4W        0  00  too 100 200 200 sw am 4co        0  00 1w 180 goo 200 sm sm   4w



          is                                      20
          U                                                                              012-  Pp

          00                                                                             009-
                                                  10
          ad                                                                             000-


                                                   5
          03                                                                             003-


          00                                       0                                     C)OO-
             0 00  i0o laO 200 2130 OM 000 400     a   00  i0o 100 900 2w sw sw 4w          0  00 100 IaO SW 200 9M SW 4M
               ,J,j






                               Hydrograph and Chemographs for Wimatma Station


         No                            06                            w
         wo    FLOW                         NH3                      20   PC
         wo                            cm

         "0


                                                                     10
         wo                            02

                                                                      41
          so

          0                  A-        00                             0
           0     IM w    m am am 4w       a 00 lw sw 2w wo aw am 4w   a 00 Ica lao 200 2m am aw 4w


          so   . . . .
          w   DO                            PO 4'                    ta- PN
          20                                                         u -

          IS                           04                            09

                                                                     00
                                       02 -


          0                            00
           a  w     w       sm no 4w      0 ao too too aw 2w sw am 4w  0 00 100 lao am wo am sw am


                                       IM                            I'Al
          u   NO                                                     12  11 P.
                            AA         80                            40
                                       IQ                            Do

          03                                                         Q3

          00
                                         0                           00
                                                       -N














           0  1* lco %w  No       -M      a 00 too wo 200 Sao aw No 4w 0 00 100 180 200 20a am sm 4w




                                     Hydrograph and Chemographs    for Cypress CreeK




                  FLOW                             12     NH3                                    PC


            10                                                                              4



            G                                                                               2
                                                   08

            0  A@                    IL            00                                       a
               0 00 lw wJD aw 2130 Sco Ono 4w         a  ao 100 lao am     boo am   4w       a  00 Im lao Roo gm goo am   4w



                                                   C64                                    08
            20   DOC                               -00   PO 4'                            Cho - PN

            to                                     02                                     G4  -

            10

                                                                                          02



                                                   00                                     00
               0 w      w       m ow wo 400           0  00 100 NO aW 2M SM NO      4W        0 w      m                  4w



                                                                                                PP
            12     3                               ao                                     06  -

            09                                                                            00  -

                                                   40

            cm                                                                            04-
                  03A
                                                   20
            as                                                                            02


            00
                                                      0                                   00
               0 w       IM             m 400         0  00 too 100 aw no wo aw     400       0 Do lco 100 boo am Sm dw   4w









Wimauma and Ft. Lonesome chemographs occur at the same time but

are not present in the Dug Creek and South Prong chemographs.

	Mean values for selected water quality parameters at these

sites during the study year are listed in Table 5.4.  For a few

parameters (pH, turbidity, ortho-phosphorus), variation between

the stations was not large and comparison of station means for

these parameters with Duncan's multiple range test found no

significant differences (p <.05) between stations.  For the

majority of the measured parameters, however, variations between

stations was large and water quality in the different sub-basins

showed clearly different characteristics.  A general discussion

of water quality at these sites based on mean values is presented

below with general reference to land use and possible

cause/effect relationships.





























                                               70
 







                                   T -,x b 1 e 5            :1         Mean valuec--, f-@,-- k4jtt*er chemisi--ry
                                                                                                   freshwater                      s@: t     t.. j. :, n               i t t: I c--..., M ari a t e e, F,':'.:L           E-@ Y



                                                                                                               C: y P) r P S7, S          LA C1           Nc., r t 1-i C: a r I t: --, n S, C-) U t h Ft
                                   Parameter Linits-                                     W i ff) .ik Lk M I C: r e v;                --.r eek             F,-T r k          D r zi. nr h           F o r k             L ci 1*1 e S C-I fn -0


                                   Spec i f i                    u (n h       s                '7171               4 229                      3                                                                 4
                                   C:,--l n cl u --- t                 /Cm


                                   p 1-1                  p H      Un i t s                     E, . C,           G1. 4                  Fl. ID               C, I. E3                E     -_4            E,       C7          C,     M-

                                                                                                                                                                                                                    -7-
                                   Tur b i d i t y                     NTLJ                                        7.     1                5. G                 4.3                    3-3 . 7

                                                                                                                                             @9
                                   Cc, I or                            PCU                       113                 78                      ID               112 1                      -38               116                      14.2


                                   TSS                                 mg/1                       5.1              8 . F,                  C:,.                 E. . ID                5. 9               4.1


                                   P-a r t i c u I at c-?
                                                                                                          -          1. 1                          -j                S3               1.15                 .74.
                                        C: a r b o n                   mQ/1                         eo                                       1                                                                                         4-5


                                   Tot al
                                   Di ss.::.]. ved                     gig / 1               15 . 7                  16.7                    11 . C)             14.9                    9. 3              13). 8            1 B. 5
                                   C-ar b on


                                   Pa, r t i c u I a t, e
                                        Ni tr ogen                        (TIQ                                              11.                     11                 08                   00                      04                 C) 3,

                                                                                                                            .2-4                     11                  C7                  08                     (7                 -)S
                                   NH3 Cas N)                             Mg / 1                   .08

                                   NO arNO , (N'                          giq    1                 5 5                                             1 .    I            GO                I . 70                                        1 IF)


                                   Par t i C U I at e
                                   Ph osp h or US                         Mg                        0@                                                                                                              C
                                                                                                                                                 .04                 .(--)4                    0,3                                     (-)1


                                                                                                                                                                                                .7--7               -4                   -7
                                   PO 4 (a s F"                           Mg/                      .3-4                     C)4                  1 . C)                  37

                                   Sj. 1 i c a                            MQ
                                                                                                                                                                     E. 4,                  7.0               E, . 4.              4. e4-


                                   -J
                                                        a                 M Q    ri'l


                                      C tk I C i U (T)                    mq/1                    @9. 7                   44 .9                  C-1 S . 5                     6             - 3 5 . E,        - 2 1 - 2 1-3      14.1


                                              El I i n j. t y
                                        s C, a C: D                       gi ci./ 1.                                   5'ED, . 7               60. el                4 7 . r5l,                                        E,


                                     C: h 1                                                     17        1.                    Ej                                           p                       C,                                  -:4
                                                                                                                                                                                                                    "D


                                                     t
                                                                                                                                                    Ej Fj


                                        Si-mviple.-d mr--,nt[ily






	The Fort Lonesome station was the most upstream site

monitored on the main channel of the Little Manatee River.  Land

use in the drainage basin for this station is different from

other monitored sub-basins in that the primary land uses are open

space and pasture.  The other sub-basins have much higher

densities of either citrus, row crops, or residential

development.  In accordance with this difference in land use,

water quality at the Fort Lonesome site was distinct from the

other stations and more similar to an unimpacted, central Florida

stream.  Generally, water quality at this site can be

characterized as highly colored, slightly acidic, with low levels

of suspended matter and moderate levels of nutrients. Mean

values of color and total dissolved carbon were highest at this

station, probably reflecting the input of humic compounds leached

from vegetation and litter in the drainage basin.  For a number

of parameters, mean values were either ranked lowest or near

lowest for this station, with Duncan's multiple range test

grouping the station alone or with one or two other stations

depending on the parameter (conductivity, turbidity, total

suspended solids, particulate carbon, particulate phosphorus,

nitrate-nitrite, calcium, alkalinity, and sulfate).  Although

further examination of soils distributions is necessary, it is

suggested that the Fort Lonesome station can be viewed as a

control, indicative of relatively unimpacted water quality in the

basin.





					72











   
 



	The site most similar to Fort Lonesome was the South Fork,

which was the only station on that branch of the river.  Mean

values of alkalinity and chloride were ranked lowest for this

station, and a number of parameters were ranked second lowest

only to Fort Lonesome (conductivity, turbidity, total suspended

solids, particulate carbon, particulate nitrogen, calcium and

sulfate).  For some other parameters (total dissolved carbon,

ammonia, nitrate/nitrite, ortho-phosphate, and silica), the South

Fork was ranked near the middle of the seven stations.

	Of the remaining five stream sampling stations, two sites

(LMR near Wimauma and LMR North Fork) were on the main channel of

the river while three stations were on three tributary creeks to

the main channel.  These three tributaries, Carlton Branch, Dug

Creek and Cypress Creek, all flow from north to south and enter

the Little Manatee on its northern bank.  Land use in Carlton

Branch is primarily agricultural with extensive citrus groves and

row crops.  Land use in the small basin (3.6 square miles)

upstream of the Dug Creek sampling site is mixed with low density

residential, citrus and fish farms.  Cypress Creek drains an area

of residential development where there was extensive highway

construction durign the study year.  Water quality for these

three tributaries to the Little Manatee were grouped together by

the multiple range test, and with a few exceptions, were ranked

1, 2, and 3 with regard to mean values for specific conductance,

alkalinity, calcium, ammonia, particulate nitrogen and

particulate carbon.



					73












      
 




	In general, water in these tributaries was lower in color

and more highly mineralized than water in the main river or the 

South Fork.  This degree of mineralization was particulary

reflected in high mean values for specific conductance (322 to

528 mg/1), calcium (35.6 to 66.5 mg/1) and sulfate (38.0 to 166.5

mg/1).  Cypress Creek was notable for the high levels of

turbidity, total suspended solids, particulate carbon and

particulate nitrogen, probably reflecting the soil disturbance

and resulting suspended load that was generated in the sub-basin

during the study.  Dug Creek and Carlton Branch had the lowest

mean color values found in the study (39 and 38 mg/1), but had

the highest levels of nitrate-nitrite and silica.  It is believed

that the high degree of mineralization and dissolved constituents

in these three tributaries are the result of irrigation runoff.

High levels of silica, calcium, and sulfate are characteristic of

ground waters in the region.

	As discussed in Chapter III, substantial groundwater pumping

occurs in the Little Manatee basin for agricultural irrigation.

Also, the USGS reports that runoff to Cypress Creek is

supplemented by spray irrigation in the basin.  High levels of

nitrate-nitrite and ammonia in these tributaries may also result

from runoff transport of fertilizer.  Upcoming investigations are

to confirm the occurrence of irrigation runoff in these

tributaries.  Runoff-rainfall relationships discussed elsewhere

in this report show that baseflow levels in these creeks are




						74











 





higher than the other basins and likely supplemented by

irrigation runoff.

	The three stations on the main channel of the Little Manatee

River are Fort Lonesome, LMR North Fork, and the LMR near

Wimauma.  Examination of mean water quality values for these

three stations demonstrates the increasing mineral and nutrient

content of the Little Manatee as it flows to Tampa Bay.  Some

constituents, such as nitrate, silica, TSS and sulfate show

significant levels of enrichment proceeding downstream while both

particulate and dissolved phosphorus show little or no

enrichment.  Although Cypress Creek flows into the Little Manatee

below the LMR near Wimauma site, data from near Wimauma can be

considered as indicative of the net water quality flowing to the

estuary.

	Mineral and nutrient enrichment of the Little Manatee River

is also seen in the additional water quality samples that were

taken on May 17 and September 21, 1989 (see Figure 5.1).  Average

values for selected water quality parameters at ten of these

stations plus average values for four of the regular stations on

the same two dates are listed in Table 5.5.  The stations are

grouped according to which region of the Little Manatee drainage

basin they occur.  Group A stations in Table 5.5 are located in 

upper part of the drainage basin near the Fort Lonesome site.

These stations are characterized by relatively high color and low

values of specific conductance, sulfate, and at three of the four

sites, silica.  Silica values were high at station 5 in Hurrah








					75





 











                                                                                                         ater quality parameters sampled on
                    lable 5.5. Averaqe values for w
                                                  May 17 and September .21, 19BB at select-ed stations in
                                                   Fiqure 15.1.

                   ------------------------------------------------------------------
                                                                         Circ-up A Stati. c-Ins                                                                          P Statigns


                   St at i ---,n                Lin j. t s                                                                                                                               D


                   S P (--- C i f i C           U (n1h ---I s
                   Crin d U C t -                 c m                182.1                 184                  1 BE.,             1 E, 5.                            14 131


                   pH                   pH units.                                           7.(                  F, . 2             6.9                               F, . ID           E,     ED

                   Col or                       FCU                  140                   115                                      1017                              115                   P)-7,


                                                                                                 7,                 -)5
                   NI-6 (N:)                    (Tig

                   NO __FNO               N)     mg        1           62:,                  GO                    0.,1,           .22                                   14

                   P04 (P)                      mg/l
                                                                                             30                 .44                  3) C)                            .41


                   Silica                       mg/l                    2.9                   -,--,.5              7.4                5 . '.2                         7.4

                   C a                          mg/l                      19                     13                  7                14                                 15

                   Alkalinity mg/l                                         46                    .4 G                                 44                                 4C)               4 33

                   Chloride                     mg/l                      I'D                    1-,                                  11

                   Sul fate                     rrjQ/l                                           16                    is             13                                 14                7 51


                   Total Dis-
                   sol ved                      mc:l                      17                     12.                   A.               17                               14
                   Carbon



























                                                                                                             /E












                                 Tab 1 e 5. 5. (Cont i nued)


                                 --------------------------------------------------------------------
                                                                                                                                         2L12-
                                                                                IS, -L. a        r.,                              -S f        J.                                              -L -I n

                                 St at i on                    Un i t s            7                          E                          15           141.                      R             I C-I



                                 Spec i f i                    UMhOS/
                                                                                                    1 -7p
                                 C.':c,ndL.tCt.                cm                 I I-D 31                              t;          S' 10                                       1


                                                                                                                   -7                    -7
                                 pH                      P 1-1 U 1-1 i t El        7 . `2           F, . 0                                             7.4                      0. 19         ---      7. 27'

                                 Cc. I or                 F'CU                        G7             33 7           -12 7                40             EA                      1 '33 7       117          @D


                                 W@ (N)                      mQ/l                      C)I                            C)I                .1              01                     0121                       0 :2:1

                                 NO &-NO                N') mg / 1                 1.7              1 .           I . 4                                 14                      E@            .71        .47

                                                                                                                                                                                              17
                                 P0 4 ( P)                     mg/l                                 .11                                  lB           .19                  .30

                                 Si I i ca                     ma/l                 4.              4.7            9.2                   1    a       130. 8                    4.2           7.(-)      7.9


                                 C                             mg/l                   1.8             18              41                 97             87                      24            40           1:0

                                 All.--.alinity mg/l                                    -..G           20             76                 75                  -                  44            59           G 8

                                 Ch I or i de                  Mg / 1                21. 1            17                                 17              16                     16            15           is

                                                                                                                                                                                              6C           9
                                 SL(l f ate                    mg/l                     is                                               2 G, C          @.)9                   17                -          C)


                                 Total Dis-
                                 s -_-, I v e d                mg                                   El. 7                                9. F,          9. 9                    1 El          14     1       2'
                                 C a r bc, n


                                 --------------------------------------------------------------------





                                                          and m,--,derz--:kte nit'r.---ate-nit-r-ite concen                                           41- r a t i     r i       w c--, r e f 1-1  u n d a t


                                      --itatic-ns 3 and 4 in Alderm,-trjs C'.reek.


                                                    GrIDUFj B stations are in the SOUth F,--,rl:: --,f the river,

                                                                              4
                                      EkS P)@E-Vil-'LlSlv d@'SCLASSECl. hzi- t,,,Fcter CjLAEdj.-'-\/ MCIE;t                                                                                   tCl the
                                                                        d                                                                       Ll

                                       Fc-rt Lones-c-Ime r-rrea.                               TI-jerce appears to be considerable enrichment

                                      Of the CSIDUth                                  fcir      sFvEr,-'-kl cc,rist-ituents-@


                                                                                                                                            p I' C g r E2
                                                    4-         -.j.     i t                                                                                  -=incl lh-cm, up:-trc--eam





station 2 to the regular South Fork station which is just above

the north fork confluence.

	Group C stations are located on Pierce Branch and Carlton

Branch which both flow into the Little Manatee North Fork.

Station 7, on the lower reaches of Pierce Branch, has water

quality similar to the upper station (#9) on Carlton Branch.

Station E, the regular sampling station on Carlton Branch,

however, has markedly higher concentrations for a number of

parameters (conductivity, silica, calcium and sulfate) probably

due to irrigation runoff to this stream.  Closer investigation of

land-use in the Pierce and Carlton Branch sub-basis should

establish the water quality effects of various agricultural

practices.  Group D stations are two small tributaries which

drain into the river downstream from the Carlton Branch

confluence.  These stations had some of the highest levels of

specific conductance, silica, calcium and sulfate concentrations

of any sites monitored during the study, presumably due to runoff

from groundwater pumping.  Interestingly, however, neither

nitrate-nitrite nor dissolved phosphorus  concentrations were high

for these streams.

	Group E stations are listed to show the increasing mineral

content of the north fork of the Little Manatee as it progresses

downstream between the confluences of Carlton Branch and the

south fork.  In a distance of approximately four river miles,

increases are seen in conductivity and silica by near a factor of

2 and sulfate by a factor of 5.  This small geographic region


					78














 




will be examined in detail with regard to land-use to investigate

the causes of these water quality changes.


Chemical Transport from Sub-basins

	As was discussed in the Data Reduction section, the annual

flux of dissolved and particulate nitrogen, phosphorus, and

carbon and total suspended solids were calculated using two

different approaches:  extrapolation and interpolation.  The first

approach is accomplished by developing rating curves and

integrating these over the annual hydrographs.  Two interpolation

procedures were used to calculate annual fluxes.

	Because the rating curves potentially provide information

from which other conclusions can be drawn these results will be

discussed in the next section.  Following that, annual flux

estimates based on both the extrapolation and interpolation

approaches will be presented, compared and discussed.


	Rating curves.  The results of the least square regression

fit of the data for the various parameters to discharge are given

in Table 5.6 for each gaging station.  For dissolved

constituents, significant rating curves could be established for

DOC, phosphate, total suspended solids and particulate carbon for

all of the gaging stations.  Nitrate and particulate nitrogen

rating curves were significant for all gaging stations except

Carlton Branch and Ft. Lonesome, respectively.  These gaging

stations had nonsignificant rating relationships for particulate




					79





 













                                                     TABLE


                          r2               Rating Relationships for Gauging Stations*
                             values underlined represent non-significant relationships)



                                           DOC                             N03                             N"H3
                                   a       b       r2             a       b        r2            a       b        r2

     LONE                        0.14   2.92    0.43            -0.16  -1.95    0.14           0.06   -3.37    0.01
     CARL                        0.28   2.41    0.44            0.09    0.41    0.01           0.35   -2.92    0.11
     SP                          0.22   2.47    0.42            -0.32  -0.87    0.36           0.12   -3.34    0.02
     DUG                         0.12   2.60    0.19            -0.15  -0.54    0.11           0.13   -2.25    0.04
     WIMA                        0.23   2.31    0.48            -0.07  -0.62,   0.03            -0.15 -2.60    0.05
     CYPR                        0.06   2.85    0.22            -0.42  -2.19    0.56            -0.18 -1.95    0.32



                                           P04                             TSS                            PC
                                  a        b       r2             a       b       r2             a       b        r2

     LONE                        ..0.10 -0.97   0.40            0.16    0.70    0.22           0.19   -0-79    0.24
     CARL                        0.31  -0.98    0.67            0.32    1.97    0.45           0.26     0.31   0.26
     SP                          0.20  -1.36    0.82            0.34    1.17    0.50           0.33   -0-54    0.48
     DUG                         0.29  -1.96    0.19            0.31    2.42    0.55           0.35     0.73   0.42
     VaMA                        0.18  -1.34    0.44            0.38    1.00    0.20           0.40   -0.93    0.23
     CYPR                        0.24  -2.98    0.30            0.21    2.42    0.28           0.23     0.46   0.36





                                           PN                             PP


                                  a        b       r-             a       b

     LONE                        0.13  -3.87    0.06            0.17   -4.20    0.10
     CARL                        0.29  -2.56    0.16            0.56   -3.01    0.35
     SP                          0.41  -3.51    0.41            0.18   -3.79    0.16
     DUG                         0.38  -1.70    0.30            0.21   -2.70    0.22
     MMA                         0.37  -3 ).71  0.15            0.14   -3.68    0.03
     CYPR                        0.26  -1.95    0.28            0.13   -2.83    0.06


      Parameters listed are for the general equation: In C      alnQ + b







 phosphorous and all but two (Carlton Branch and Wimauma) had

non-significant relationships for ammonia.

	The lack of observed significant rating relationships for

ammonia for most of the gaging stations is not surprising given

the variability of nitrification and denitrification in the

watershed.

	In general, the significant rating curves for a given

parameter are similar for all gaging stations.

	Fluxes from Sub-basins.  The annual fluxes of dissolved

organic carbon nitrate, ammonia, phosphate; particulate carbon,

nitrogen and phosphorous; and total suspended solids from the six

sub-basins of the Little Manatee Watershed were estimated using

the three methods described in the water chemistry data reduction

section.  Result of the two methods which gave the best

agreement are presented in Table 5.7.  These estimates of fluxes

for each constituent for each gaging station were used to

calculate mean annual fluxes.  The poorest agreement was observed

generally for the smaller sub-basins.

	The total fluxes of the various constituents due to

discharges from all sub-basins are presented in Table 5.8.  The

relative contributions to these fluxes from each sub-basin are

also given in this table.  Fluxes of dissolved nitrogen and

particulates from Carlton Branch, Dug Creek appear

disproportionately high on the basis of comparison to watershed

size or discharge.


					81













 








                                                                         TABLE


                                            Annual Flux of Dissolved and Particulate Nutrients
                                              and Total Suspended Solids From Sub-Basins of
                                                             The Little Manatee River






                                                                                   Kilograms Per Year


       Sub-Basins                                    DOC       N03        NH3         P04        PC            PN         PP       TSS
                                                     xl()5     x,03       x,03        x,03       x,03        x,03      x,03        x,04


       Ft. Lonesome                     1            10.3      4.72      1.62         19.4       27.7          1.12       0.87       0.4
       (LONE)                           1)           10.8      4.30      2.34         18.9       39.4          2.11       1.36     17.2
                                 Mean                10.5      4.51      1.98         19.2       33.5          1.61       1.12       8.8
                                        S.D           0.4      0.30      0.51          0.3          8.3        0.70       0.35     11.9

       Carlton Branch                   1             1.70    21.5       0.86          5.82      20.5          1.18       0.97     11.2
       (CARL)                           2             2.46    30.9       1.26          7.07      31.5          2.01       1.06     16.1
                                 Mean                 2.08    26.2       1.06          6.44      26.0          1.59       1.02     13.6
                                        S.D           0.53     6.7       0.28          0.88         7.8        0.58       0.06       3.5

       South Prong                      1            .10.69   15.4       2.49         22.4       72.3          4.66       1.84     41.0
       (SP)                             2             9.05    11.6       2.41         34.6       96.0          5.96       2.39       3.61
                                 Mean                 9.87    13.5       2.45         28.5       84.2          5.31       2.12     38.6
                                        S.D           1.16     2.7       0.06          8.6       16.8          0.92       0.38       3.5

       Dug Creek                        1             0.65     3.29      0.51          0.71      10.7          0.96       0.33       5.7
       (DUG)                                          0.69     3.73      0.67          2.08      45.2          2.99       0.58     16.5
                                 Mean                 0.67     3.51      0.59          1.39      27.9          1.97       0.45     11.1
                                        S.D           0.03     0.31      0.11          0.97      24.4          1.44       0.17       7.7

                                                                                                            1 '7. 1
       Wimanma                          1            40.6     85.0       9.57         8 7. 4    319            1          7.36     197
       (WIMA)                           1)           41.8     75.3       8.10         82.4       349         19.4         9.25     191
                                 Mean                41.2     80.1       8.84         84.9      334          18.2         8.31     194
                                        S.D           0.8      6.9       1.04          3.5       21            1.7        1.34       4

       Cypress Creek                    1             2.54     1.57      1.88          0.88      26.9          2.51       0.92     18.7
       (CYPR)                           2             2. 5 4   1.35      1.75          130       '35.3         2.92       1.61     241.2
                                 Mean                 2.54     1.46      1.82          1.09      31.1          2.72       1.27'    21.5
                                        S.D           0.00     0.15      0.10          0.30        6.0         0.30       0.49       3.9















                                                                TABLE





                                         Annual Material Fluxes to the Little Manatee Estuary
                                              and Relative Contributions from Sub-Basins







                          Total          LONE         CARL        SP          DUG         WIMA        CYPR         IB2
                          (tons/yr.)                                      (Percent)


           DOC            4370             24            5        23            2             94          6        41
           N03              81.6             6           32       17            4             98          2        40
           NH3              10.6           19            10       23            6             83         17        26
           P04              86.0           22            7        33            2             99          1        34
           PC               365              9           7        23            8             92          8        44
           PN               20.9             8           8        25            9            .87         13        37
           PP                9.58          12            11       22            5             87         13        38
           TSS            2160 3             4           6        18            5             90         10        56
           Watershed        451            19            4        27            2             95          5        52




                  1       Total is calculated as the sum of the fluxes measured at the Wimanma and Cypress
                          Creek gauging stations.
                                 C7     0

                  2.      IB refers to the inner basin. Fluxes are calculated as the difference between the
                          flux at Wimanma and the sum of the fluxes at Dug Creek, Carlton Branch, Ft.
                          Lonsome and South Pron,-.
                  3.      Watershed area is in km2.



	Total fluxes given in Table 5.8 are conservative estimated

of the amount of material delivered to the Little Manatee estuary

because we have not considered smaller sources of materials such

as direct surface runoff and contributions downstream of the

gaging stations.  We also have not considered removal processes

that may be occurring downstream of the gaging stations.

	The efficiency of material mobilization from each sub-basin

is compared in Figures 5.3 A and B.  Figure 5.3 A compares the

flux of dissolved substance per unit area and Figure 5.3 B does

the same for particulate substances.  These comparisons can be

used to distinguish similar watersheds and perhaps identify the

influence of different land use practices.

















					84





 










                       Q16
                                                                        DOC                      006
                                      0                                                                                                              NH3

                       Q10


                                                       0
                                                                                                 004

                       0,06

                                                                                                                0
        c\j                                                                                      002
           E           0.00
                                                                                                 000
          0)                 0         100        200        300        400        6W                  a         100       200        300         400        600

                                                                                                   0.4
                                                                                                                                                     PO                            Cj
         X                                                                NO
         :D                                                                  3                                                                         4
             1                                                                                     0.3
         LLI_

                                                                                                   02



                                                                                                                                 0
                                                                                                   OL1


                                                       0
                         QO            01                                                          00
                             0         100        200                   4W         Wo                  0         100       200                    4W         6W


                                                                WATERSHED AREA (kM2)
                              Figure             Flux per unit area of dissolved nutrients for sub-basins of the Little
                                                 Manatee River Watershed plotted againS                    t sub-basin area. Symbols are
                                                 defined below.
                             LONE              CARL                 SP                DUG              WIMA               CYPR               NP

                                                                                      A










                                                                                                                     3
                                                                                         TSS                                                                         PC


                                       08                                                                            2

                                                                      0
                                                                                            13
                                       04 -


                    04                 OL2 -                                                                                                     0
                        E
                        V                            0                                                                          0
                                       CLO                                                                           0
                                                                200         3W         400        600                 a
                                                                                                                                100        200         300         400       600

                                     OL20
                       X                                                                 PN                                                                          PP

                                     C1 16
                                                                                                                  004   A
                      LL


                                     CLIO


                                                                                                                  aO2                                                 93


                                                    0
                                     Q,OO                                                                         0100
                                           0                    200        300         4,00       60a                 0         100        200        WO           400       600


                                                                                WATERSHED AREA                                  (km    2
                                           Figure_'S_3@- Flux per unit area of total suspended solids and particulate nutrients
                                                              from sub-basins of the Little Manatee River sub-basin area.                                   Symbol s
                                                              are defined below.

                                           LONE              CARL                SP                 DUG              WIMA              CYPR                NP
                                                                                                    A





VI.	ESTUARINE WATER CHEMISTRY


OBJECTIVES

	An overall goal of the Little Manatee River Project was to

examine the relationships of the quality and quantity of

freshwater inflows to the ecological characteristics of the

Little Manatee River estuary.  A central component of this

investigation was the monitoring of salinity and water quality

conditions in the estuary during the study year.  Data collected

within the estuary were synoptic with the freshwater stream

sampling so the effects in the estuary from short term changes in

freshwater inflows could be examined.


SAMPLING AND ANALYTICAL METHODS

	Estuarine water quality sampling was conducted on a bi-

weekly basis with 26 sampling events occurring during the study

year (January 24, 1988 to January 24, 1989).  Sampling in the

estuary was coordinated with the freshwater sampling regime and

on 24 dates estuarine and freshwater samples were collected on

the same day.  on two dates, freshwater samples were collected

the day befor the estuarine sampling.

	Estuarine field sampling included a combination of two fixed

location stations and several stations which were located on

specific surface salinity concentrations (Figure 6.1).  The first

fixed location station was located in Tampa Bay northwest of

marker #1, approximately 2.3 miles from the river mouth



					87









 







        River mlfles - Little Manatee River Estuary




                                                                          GO I f
                                                                           Of
                  q                                                      MEX11CO




                                                      RAIS KJN INUT                       _j
       it
                                                             @j W-@Y

                                "t6-.



                                                           U, 41
                                                             3




                                                                  LITTLE MANATEE
                                                                        FtIVER








                                                                                   _Zn

                                                                                    10


                     1     Reference. locations of es-tuarinc sampling %tations in Little
                           Karw-tee River and Tampa Bay, Fixed locations are shown by all X
                           @-n Tampa Bay and Ruskin Inlet. Mileages ahown provide refe-rutter,
                           fo,r values listied in Table 6,1 for stations -based -on saliniry
                           Concentrations.
                                                                          Gulf
                                                                           011COX
                                                                         MEX

































































                                                   op





following the boat channel.  The second fixed station was located

in Ruskin Inlet, a channelized tributary to the Little Manatee

River approximately 2.5 miles upstream of the river mouth.  The

locations of the remaining sampling stations were flexible and

based on the location of selected surface water salinity

concentrations on the that sampling day.  For the entire study

year samples were collected at 18 ppt and 9 ppt salinity

concentrations.  The 0 ppt salinity station was determined by the

location of surface water near 1000 umhos/cm specific

conductance.  For the first two sampling trips, samples were

taken at the 9 ppt salinity concentration, but this station was

discontinued and for the remaining 24 trips samples were taken at

the 12 ppt and 6 ppt salinities.  River mile locations were

recorded for all samples collected on salinities.  The locations

of these stations during the study year are listed by rivermile

in Table 6.1, while a map of the estuary showing river mileages

is illustrated in Figure 6.1.

	All estuarine water quality sampling was conducted in the

morning or early afternoon on an incoming tide.  At each station,

duplicate water samples were taken from both surface and bottom

waters.  Water samples for chlorophyll analyses were kept chilled

and transported to the Florida Department of Natural Resources

Laboratory in St. Petersburg where filtration of the sample for

pigment removal was done the same afternoon.  As with the fresh

water samples, filtration for the separation of particulate (C,

N, and P) and dissolved nutrients (PO_ NO_ & NO_ Organic



				89







 










                          Table 6.1.                     Location of Little M@rnatee Piver salinity stations and
                                                         the Tampa Bay station by rivermile.                                                                Pivermiles werc-
                                                         measured as distance from the mc-uth.                                                                Neaative numbers
                                                         indicate distance into Tampa Bay measured in the channel
                                                         from navigation marker #1. Positive numbers are
                                                         distances from the mouth toward the head of the river.


                          -----------------------------------------------------------------


                                                    Tampa                                                                                                                        Rus. k i n
                          Date                       Bay                           113ppt                  12- > p p t            Gppt                     Oppt                  Inlet



                            1 1-71E                              @7*                                           N.D.                    N.D.                      @.7                      j
                              Ie- -/88                                                                                                                           '1
                          02, / 10                                                      0 . -31 1              N.D.                    N.D.                      6- @ I
                          -2/,-                                                                                1.
                                   A                                                         44                                            4                     G. 5
                          0    C) 9                                                     C). 00                                             0 0                   -1 . G, 5
                                                                                        1.                     -C.18                   1 . 5j'S                  C1. . 1. 5
                          4 'C)E,
                             /                                                                                 @.. 11                  E,. 0C)
                          C) 4                                                          1. 3C)                 33, E, C)               S . '725                  S. 4 r5i
                          05/04-                                                        1 . S15                'Ed, . 7 0              El. 151                   C- . 33 5
                          05/ 18                                                        2.55                   6. IC)                  7 . 223                1 C). 223
                          06/01                                                         3. 70                  5.65                    E   3 C)               10. 46
                          OE/ 15                                                        4. BC)                 G . 60                  S.GC)                  1 (). 4 5
                          C) F, /'29                                                    5. 10                  El. 16                  9. E-0                 10. 63
                          C) 7/14                                                       31. 50                 5. 19                   8.34                      9.25
                          0 7 /,2, B                                                    1. 4-0                 3. 50                          C)                 7.19
                                                                                        C). 0C)                                                                          24
                          C)S/ 10                                                                              ( . '*:' 4                    15                  4. *@
                          08/30                                                         1 . -'23           -0.91                       0. 00                     3:1. 40
                          019/0e                                                    -2.1()                     T.BAy**                 0-81
                          0 E) / * _2 1 2                                         T. Bay*-)@-                  I . 533                 4. J.C)                   F,      -25
                          1 C-)  I I                                                T.Bay**                    -0.45                                                     '---'5
                          1                                                       -0. 1.9                      i . 0 C)                                                  I
                          11 /07                                                    -        4-15              -1.1e                   1.4-C)                    4. 55
                                                                                        C.,                    -)  9                       -7 0                          S '71
                                                                                                               C r,                    4.;_                              -1
                                                                                                                                       .7'. @ (')                        -
                          12-1                                                      --1. 4F,                   0. SO                                             7. 1,-@
                          12                                                               Ok")                    r-., 1.             4 . E. c5
                                                                                                                        C)                                               S




                                                                                                                                       +         -7
                          Averaoe                                                   +().                       +'7'.    1                                                                   j k-)
                                                                                               J
                          Range                              0                                C)                   5) @-:j                 8 1.
                                                                                        1:1       1            to S.     G, C          tr,


                          -----------------------------------------------------------------


                          *'Fixed location
                                                                                                     c @.:k        TZMT p
                                   I i n i t y           oriC EFit r Ekt'i, F1 I'CILAFI I                      t              EA h"     \Y S .!--,IFA t i     r-1





Carbon) was done in the field with resulting filters and

filtrates put immediately on ice.  Samples (filters) for

particulate phosphorus analysis were periodically shipped to

SL&ES for digestion and measurement.  Remaining water chemistry

parameters were analyzed at the District Laboratory in

Brooksville.  Water samples were analyzed for the parameters

listed in Table 5.1, using the methods indicated.  All

statistical analyses and presentations of these data are based on

the mean of duplicate samples.

	At each water quality station, vertical profiles of

temperature, dissolved oxygen, pH, specific conductance and

salinity were made at 1 meter intervals plus bottom with a

Hydrolab Surveyor II water quality meter.  Also, at each station,

a light penetration profile was taken with a Li-Corr photometer

by measuring ambient (deck) and in-water light intensities at .5

meter intervals plus bottom.

	Beginning with the third sampling trip (February 24, 1989),

additional measurements were made throughout the estuary for

vertical profiles of temperature, dissolved oxygen, pH, specific

conductance and salinity.  These measurements were performed

during what is termed a "Hydrolab run", where numerous fixed

locations in the river were sampled within a one hour period.

After water chemistry samples were collected on an incoming tide,

Hydrolab runs were performed in the mid-afternoon on a slack,

high-tide condition.  Stations for the Hydrolab run were at fixed

locations extending from the river mouth to 9.5 miles upstream,




					91




 










           with extra meaSUrements taken ifurthrre tAPstream during two

           saffi,-)ling events. The Hydrolat? run was initiaVed to measure in

           situ physical parameters throughout the estuar:y on as similar

           conditions as possible. Similar sampling had been done in the

           Little Manatee River by the District between 1965 -and.1987.   Muc h

           of the analyses regarding salinity distributions and dissolved

           oxygen relationships in the river are based on the "Hydrolab

           runs" made from 1985 to 19B7 plus the study year.




           DATA REDUCTION


                Advection-diffusion models have been used by many

           investigators to interpret estuarine chemical data- (e.g., Li  -and

           Chan, 1979; Kaul and Froelich, 1984). Thege models use salinity

           as a tracer.   The distribution  of a-constituent in estuarine

           waters can be compared to salinity to determine whether a

           substance is: 1) conservatively transpprted through the estuary,

           (2) removed from the water column or (3) added to the water


           column due to local input (e.g. anthropogenic, release from

           sediments, etc.). These types of estuarine behaviors are

           demonstrated in Figure 6.2.
 L.

                From the advection-diffusion models using salinity as a

           Conservative tracer, the intercept of the extrapolation (or

           tangen't) of the constituent-salini-It-,y curve at the high sali nity

           end of the curve where change in constituent concentration with

           change in salinity is constant, is defined as the apparent zero

           salinity endl--4ember (AZE).  It can be demonstrated mathematically


                                            92












                                         A      -AZE
                                                                       C:



             V'2DD-
                      AZE                                            C) :C:z)
               iDD
             U
                 0                                                   D
                   0     10     20     3D      0    10. 20   3D

                                AZ&-                   C




                         D




                                     IIC)    210    310
                                     Salinity (%C))









         Figure .9-M. ENamples of  different estuarine behavior of trace
              metals: (a)   removal (after Faqueres et a!., 1978); (b)
               conservative; and (c) release (Windom, unoublisbed data).





that river discharge multiplied by the difference in the observed

zero salinity concentration and the AZE value gives the rate of

removal, or release, or the constituent, per unit time, necessary

to produce the observed concentration distribution.  The only

assumption required is that the concentration of the constituent

in the freshwater input is constant over the residence time of

the estuary.  For the Little Manatee estuary, this assumption is

satisfied sufficiently to draw the conclusions that will be made.

	Following the approach described above bimonthly data for

concentrations of dissolved nitrate + nitrite (No ), ammonia

(NH ) orthophosphate (PO ), organic carbon (DOC); total suspended

solids (TSS); and particulate carbon (PC), nitrogen (PN) and

phosphorus (PP) were plotted against salinity.  The zero salinity

concentration was taken to be the mean value of the bimonthly

concentrations observed at the Wimauma and Cypress Creek gaging

stations weighted by their mean daily discharge at the time of

sampling.  This value was then plotted on the constituent vs.

salinity curves for each month.


RESULTS

Salinity Distributions

	Streamflow levels in the Little Manatee River typically have

large seasonal variation with resulting effects on salinity

distributions in the estuary.  Streamflow characteristics for the

Little Manatee River near Wimauma based on over 50 years of

record were presented in Chapter II.  In sum, the river



					94








 







              experiences prolonged low-low periods, usually in the spring or

              fall, when daily flows average less than 50 cfs. Conversely,

              brief periods of heavy rainfall rapidly increase streamflow in

              the basin and short-term flows over 1000 cfs are not uncommon.

                  As described in Chapter IV, an unusually wide range of

              streamflow levels occurred during the study year.   Estuarine

              water quality and salinity sampling during January through March

              corresponded to medium to medium-high flow levels for the river

              (71 to 429 cfs daily flows). Beginning in April, a prolonged

              period of generally diminishing flows occurred which were lowest

              in mid-June (15 to 20 cfs) and extended-into early July.     Summer

              rains began in mid-July and flows were at moderate levels for the

              remainder of that month.  The first high flow levels (1050 cfs)

              occurred during the August 10 sampling event, and extremely high

              flood flows (9720 cfs) were recorded in early September after

              four days of heavy rain.   Flows generally returned to low to

              moderate levels for the study year, although storm events raised

              flows to 414 and 493 cfs in November 1988 and January 1989,

              respectively.

                   Salinity distributions in the estuary showed distinct

              changes in response to these changes in flow.    Mean water column

              salinity for four fixed locations in the river are plotted by

              date in Figure 6.3.   Salinity at the mouth of the river remained

              above 20 ppt, until early September, when flood flows briefly

              reduced salinity to near 5 ppt.   For the remainder of the year,

              salinities fluctuated between 18 and 23 ppt salinity, with slight


                                               95
 








                                             MILE 0.0

                   30









                   20





                   Z



                   10





                     01
                   05DEC87    14MARBS    22JUN88    30SEP88    08JAN89    18APR89

                                                DATE


                                            MiLE 4.23

                   3








                   20


                  -C@


                   Z


                   10@






                     01
                   05DEC87    14MAR88    22JUN88    30SLP88    OSJAN89    18APR89

                                                DATE





        Figure 6,1.    Mean water collmn salinities at four locations in the Little
                       Mar-tee River, February 24, 1988 to Janu.-a7 24, 1989.







                                                     ,MILE 7.19



                             17
                             16
                             15
                             14
                             13
                             12
                          0-11
                             10
                             9
                         Zj  8
                         V)  7
                             6
                             5
                             4
                             3
                             2


                             0
                          05DEC87     14MAR88     22JUNB8     30SEPBB     OBJANS9      IBAPRB9

                                                          DATE


                                                      MILE 9.53

                             11


                             10


                             9


                             8


                             7


                             6


                          z  5

                          V) 4


                             3


                             2





                             05DEC87   14MAR88     22JUNSB    30SEP88      OSJAN89     18APR89

                                                          DATE








                Figure 6..t.     (Continued)




decreases in November and January due to storm events.

	Salinity at mile 4.23 (Figure 6.3b) displayed a much wider

degree of fluctuation.  Salinity steadily increased in the spring

and early summer in response to the continuing dry season.

Salinity was highly variable the rest of the study year, ranging

from 9 to 3 ppt after four storm events to values above 10 ppt

during a dry spell during December and early January.

	The other two stations (mile 7.19 and mile 9.53) presented

in Figure 6.3 show a similar trend with regard to salinity.  Both

stations were essentially fresh in the early part of the study,

but salinity increased beginning in April and continued with the

dry season until early July.  Increases in flow during the summer

rainy season reduced salinities to low levels, and for the

remainder of the year, they remained near fresh at mile 9.53 and 

below 3 ppt at 7.19.

	Seasonal changes in salinity distributions are also

described by longitudinal profiles of mean water column

salinities on selected dates which are presented in Figure 6.4(a-

f).  As shown, salinity in the river below mile 7.19 were reduced

from February to March due to an increase in flow.  The maximum

observed salt penetration is shown for June 29, near the end of

the dry season, when salinities above 20 ppt were found six miles

upstream and salinity at mile 10 was near 8 ppt.  Salinity in the

river decreased through July and August, and the river was

completely fresh except for a small salt lens at the mouth during

the flood in early September.  By late September and



					98






 






                                       FEE3. 24      and   MAR. 22         1988

                             30








                             20





                           z



                             10





                             01.
                              0     1    2    3     4    5    6     7    8    9    10

                                                        MILE



                                        JUN. 29 (0) and JUL.28            1988

                             30








                             20







                            Ln









                               0    1    2    3   4    5    6    7    8   9    10   1 1

                                                        MILE







              Figure          Longitudinal salinity, profiles for the Little Manatee River
                              estuary on selected dates from February 24, 1988-to Janua:ry 1989.








                                     AUG. 10 (0) c.rid AUG. 26            198 8
                          ,30-1


                          20





                       z



                          10





                           01.
                             0   .1    2    3     4    5     6    7     8    9     10

                                                      MILE



                                     SEP. 08 (o) and OCT. 24              1988

                          30








                          20
















                             0    1    2     3    4     5    6     7    8     9    10

                                                      MILE






           Figure 6:-3.      (Continued)









                                     NOV. 21        ond DEC. 16         1988

                           30








                           20







                         V)
                           10








                             0    1    2     3    4    5    6    7     8    9    10

                                                      MILE



                                      JAN.  1 1     ond JAN. 24         1989

                           30








                           20









                            10








                            0
                              0    1    2    3     4    5    6    7    5     9    10

                                                       MILE





              Figure 6.3'.    (Continued)






through the fall, salinity distributions had retained to more

typical profiles, although a significant storm event in January

1989 freshened the river above mile five.

	The salinity data presented graphically above show that

salinity distribution in the Little Manatee River is highly

variable and responds to relatively small changes in streamflow.

This phenomenon is common in estuaries and much of the estuarine

biota are tolerant of widely fluctuating salinity.  One approach

for describing estuarine ecological structure, however, is to

estimate the frequency that various salinities are encountered at

different parts of the river.

	For the Little Manatee River Project, salinity measurements

recorded between 1985 and 1989 allow the statistical examination

of salinity-flow relationships in the estuary. In Figure 6.5,

salinity at various points in the river are plotted versus

average daily flow when the respective measurements were taken.

Predictive equations for salinity as a function of flow for these

locations are being established using linear regression analysis.

Although the relationships presented in Figure 6.5 use average

daily flow at the time of salinity measurement it is expected 

that some integrated flow value, such as the preceding 5 or 10

day average flow, will give a better fit.  The inclusion of a

tide stage variable corresponding to high-tide height at the time

of sampling should also increase the fit of relationships.  The

development of equations using regression analysis will then be

compared to the flow duration characteristics of the river to


				102





 





                                                             MILE   0.0

                                  30


                                  281
                                  271
                                  26

                                 E25

                                  2 4

                                E 23

                                  22

                                  21

                                  20

                                  1 9.

                                  18

                                  17
                                    0               100             200              300             400
                                                                 FLOW (cfs)




                                                            MILE 4.23

                                  30








                                  20








                                  10









                                    0,
                                    0               100             200              300             400
                                                                 FLOW (cfs)







                 Figure 6 L4'.      RelAtionships of mean water colxmm salinity to same day average
                                    flow at four locations in the Little Manatee River estuar"y.















                                                        MILE 7.19

                               19
                               18
                               17
                               16
                               15
                               14
                               13




                               10
                                  9
                                  8
                                  7
                                  6
                                  5
                                  4
                                  3
                                  2              %
                                  1

                                  0             100              200             300              400
                                                              FLOW (Cfs)



                                                         M I L IE- 9. 5 3



                               lo


                               .9


                                  8


                                  7




                                  5
                                  41
                                  3


                                  2-





                                  0              100             200              300             400
                                                              FLOW (cis)


give estimates of what frequency various salinities are

encountered at different locations on the river.



Dissolved Oxygen

	Seasonal dissolved oxygen conditions in the Little Manatee

River estuary are examined in this report primarily from data

collected in the "Hydrolab runs" which were conducted on 24

sampling dates between February 24, 1988 and January 24, 1989.

These data are particularly useful because they were collected

throughout the estuary on similar conditions (mid-afternoon,

slack high tide), thus reducing possible confounding effects from

time of day or different tidal conditions.  Other data which may

be important for understanding dissolved oxygen concentrations in

the estuary are the physical and chemical data collected each

trip on the incoming tide before the Hydrolab run was performed.

	Dissolved oxygen (D.O.) concentrations for four locations in

the estuary during February 1988 to January 1989 are illustrated

in Figure 6.6.  D.O. concentrations were typically highest and

had the least seasonal variation at the mouth of the river.  D.O.

did show the expected inverse relationship to water temperature,

with highest D.O. concentrations found in the winter and lowest

concentrations in the summer.  The lowest instantaneous mean D.O.

level measured at this site was near 4.0 mg/1 during the early

September flood.

	D.O. concentration at mile 4.23 (Figure 6.6.) were

generally lower than at the mouth, particularly during the summer




					105



 








                                                 MILE 0.0









                     E
                     C;









                     05DEC87     14MARBS    22JUN88     30SEP88    OBJAN89     18APR89
                                                   DATE




                                                MILEE 4.23









                     E

                     0












                     05DE'.57    14MAROH    22JU1488   30SEP88     OBjA-NB9    ISAPR89

                                                   DATE





             Figure 6 . 6,  Mean water coli-m dissolved oxygen concentrations at four
                            locations in the Little MarLntee kiver estmary, February 24, 1988
                            to January 24, 1989.











                                                                 MILE 7.19











                                 ci






                                 05D@CV        .1 4MARBS     22JU'N88      30SEPBB       OBJAN89       18AP'R89

                                                                      DATE




                                                                  MILE 9.53



















                                               14MARE-B     22JUNBB       30SEP88       OZJAW89        I lull, R89
                                                                     DATE






                    Figure@     (j5,   (@,&jttnued)


0







             months. Mean D.O. concentrations below 4 mg/1 were recorded on

            five dates between July 14 and September 22, 1988. The

            September flood actually resulted in an increase in D.O. at this

            station. D.O. concentration's were more erratic at mile 7.19, but

            followed a similar seasonal pattern to mile 4.23. Low D.O.

            levels were observed during the summer, but D.O. concentrations

            increased from the September to October samples and remained high

            for the remainder of the year. D.D. concentrations showed the

            most seasonal variations at mile 9.53 where levels above 10 mg/l

            were recorded during May and October, 1988, but levels below 4

            mg/1 Were recorded between June and September.

                 In sum, D.O. concentrations in the Little Manatee River,were

            at high levels during most of the year but reduced to values

            below 4 mg/1 during much of the summer, indicating potentially

            stressful concentrations for aquatic biota in the summer.

            Differences in D.O. between surface and bottom waters were small,

            however, and it does not appear that oxygen stress occurs in

            bottom waters due to limited mixing. Generally, with regard to
                                                                  

            temperature and salinity effects on water density and

            stratification, the Little Manatee tends to be well mixed.       There

            are areas of the river, however, that appear to be sensitive to

            factors that could reduce D.O. concentrations. Longitudinal

            profiles of salinity and dissolved oxygen concentrations are

            plotted by rivermile in Figure 6.7.    Profiles measured from June

            through August show consistent declines in D.O. from the mouth

            upstream to near miles 4.0 to 7.0, with minima often occurring



                                             108






                                                JUN.115,1988

                          30;







                          20                                                     7

                        C6                                                        0



                          10








                                                                                 3
                            0    1   2    3    4   5.   6    7   8    9   10   1 1

                                                     MILE
                                                JUN-29,19881
                          30                                                     9





                         C)
                          20                                                     7
                                                                                  0







                                                                                 5








                           0'
                            0         2   3    4    5    6   7    8    9   '10

                                                     MILE









             Figure 6 -      Longitudinal profiles of mean water column salinity and dissolved
                             oxygen profiles in the Little Manatee River estuary, February 24,
                             1988 to January 24, 1989.
                            D







                                                               14, 19 8 8

                             30 1-







                             20                                                                 7

                            CL                                                                  0


                           Ln 10                                                                5




                             01.
                               0     1    2     3     4    5     6     7    8     9    10     11

                                                             MILE


                                                        JUL.28,1988
                             301                                                                9





                             20                                                                 .7


                            CL                                                                  p







                                                                                                3
                                           2     3      4     5           7      8

                                                             MILE











            Figure 6.-6.       (Continued)





                                                      A U    10,   9 B s






                              20                                                         7
                                                                                           0

                                                                                           0


                            Ln 10                                                        5




                               C)                                                        3
                                0     1    2     3    4     5    6     7     8    9      10

                                                           MILE


                                                      AUG.26,1988

                              30







                              20                                                         7


                                                                                             0



                                                                                            to


                               C)









                                                                                         3
                                0     1     2    3     4    5     6    7     8    9      10

                                                           MILE












                Figure 6.6.      (Continued)







                                                                     SEP. 08, 1988

                                       6









                                       C) 4                                                                           7



                                                                                                                      0
                                       3



                                       Ln
                                       2






                                       oll                                                                            3
                                       0      1       2      3       4      5       6                      9       lo@

                                                                           MILE


                                                                     SEP. 22,        1988

                                                                                                                      9
                                       17
                                       It 6
                                       15
                                       14
                                       13
                                       012                                                                            7


                                       9

                                                                                                                      to


                                                                                                                      5


                                       41
                                       3
                                       21
                                                                                                                    @3
                                       0       1      2       3      4      5       6      7       8       9       .0

                                                                           MILE









              F i gur e    @-6         (Continued)










			between mile 4.0 to 6.0 These minima were found over a wide
			range of salinity concentrations ranging from 8 to 22 ppt. On
			several dates, D.O. increased upstream in low salinity and freshwater
			 reaches.



                     Although not shown., D.O. concentrations at the nearest

               freshwater stream site (near Wimauma) did not reach the low(4


               mg/1) concentrations observed in the estuary.     Estuaries, because

               of their tendency to retain suspended and organic matter, are

               often sites of D.O. depression. Data to date indicate that the

               Little Manatee River estuary does not currently have a serious

               problem with low dissolved oxygen concentrations, but in many

               areas of the river, conditions are borderline and further

               perturbations could result in significant reductions in water

               quality.




               General Water Chemistry

                    Mean values for nutrients and other water quality parameters

               for the estuarine sampling stations are listed in Table 6.2.       All

               the stations, except Ruskin Inlet, are arranged with salinity

               reducing from left to right (from Tampa Bay to 0 ppt) so changes

               along the salinity gradient can be easily Visualized. The

               general water quality characteristics of the estuary are

               summarized in the discussion below.    Greater detail regarding the

               behavior of nutrients and suspended matter in the estuary is

               provided in the Subsequent section.





                                                113


















                 ---------    ----------------------------                      ------------------------

                 Tal.-J-4 e 6. 2.       Mean values @or water chemistry parameters at
                                       estuarine sampling stations                    Little Manatee
                                        River.


                                               Tampa                                                        Rus k i n
                 Parameter          Uni ts       PC        18 rip       12 mn        6. EPt      0 ppt         Inlet
                                                  :.Iy



                 Mile               miles      -2.27       0.67          2.19          4.1'37       6.76          2.5


                 Salinity         ppt          23.4        18.6.        12.4            6.4         0.6        10.6

                 Temperature OC                22.6         3 . 0        24.1          25.1       22.9         24.7

                 pH                 pH         7.3         7.0           6.9            6.8         6.7          7.2


                 Turbidity           NTU       4.6           2.9          3.0           4.2         5.8        4.13

                 Color              PCU        14          25            44             70        106           57


                 Total Sus-
                 pended Solids        mg/l     1.9.2       10.5          8.2            8.0         7.1        10.1

                 Particulate
                   Carbon           mg/l       1.18        0.84          0.91           1.25        1.30       1.46

                 Total Dis-
                   solved Carbon mg/l             6.9      7.9          9. B        11.8         14.6        11.7

                 Particulate
                   Nitrogen         mg/l        0.13         0.10        0.11           0.13        0.14       0.17

                 NF6 (as N) mg / 1             0.04         0.08          0.09          0.08        0.07       0.07

                 NO 2r_NO -x-N    mg/l         0.02        0.05          0.09           0.16        0.43       0.15

                 Particulate
                   Phosphorus mg/l             0.06        0.03         0.04           0.05       0.05         0.05

                 P04 (as P) mgll-              0.34        0.32          0.32          0.31       0.30         0.35

                 Silica           mg/ 1        0.9         2.2           2.1            3.7         4.9          3.6

                 Chlor a          mg/m         6.6         5.5          10.4           15.6       20.3         19.0


                   ----------------                           --------        ---------------------- --







                                                                 114






					
			The Little Manatee River estuary is really a functional unit

	of a much larger estuary, Tampa Bay.  The open waters of Tampa

	Bay,however, are much different than the waters of its brackish

	tributaries such as the Little Manatee River.  The progression

	from the upper reachers of the Little Manatee estuary (o ppt

	station) to the Tampa Bay station showed chemical differences

	indicative of a change from nutrient-rich,low-salinty waters to 

	phytoplankton dominated, high-salinity waters.  Nitrate-nitrite,

	silica, particulate carbon, turbidity, and total dissolved carbon

	showed distinct declines in concentrations from the upper reaches

	of the estuary to Tampa Bay.  With the exception of phosphorus,

	the bay has much lower levels of dissolved nutrients (N,Si) due

	presumably to phtoplankton uptake.  Dissolved phosphorus

	concentraions are distributed very evenly along the salinty

	gradient with mean values ranging between .30 and .34 mg/l

	indicating this nutrient is not limiting and is in excess supply

	in the estuary.  Total suspended solids were highest in Tampa

	Bay, and increased with salinity in the river due to the 

	influence of bay water.

			The Ruskin Inlet station, listed on the far right of Table

	6.2, was located in an urbanized tributary to the Little Manatee

	that receives considerable amounts of urban runoff.  Of course,

	salinty fluctuated much more at this station than at the

	water salinty at Ruskin Inlet ranged from 0.0 to 22.0 ppt during

	the course of the study and averaged 10.6 ppt.  Nutrient

						115


				







		concentrations showed large seasonal variations at this station
		due to stormwater inputs and the rapid change from a mesohaline
		(medium salinity) to a low salinity environment.

		Nutrient and Suspended Solids Distribution
			The results of the analyses of dissolved and particulate
		nutrients in estuarine samples are plotted against salinity in 
		weighted freshwater concentration of a substance to its
		concentrations at higher salinities provides a basis for judging
		estuarine behavior of the substance as discussed in the data
		reduction section. For this purpose, the trend in the data for 
		concentration versus salinity connecting weighted mean freshwater
		concentration to concentration at highest salinity is interpreted
		as discussed earlier.  The following discussion summarizes the
		behavior of the nutrients based on their estuarine distributions.

		Dissolved Nutrients  DOC is observed to behave
		approximately conservatively throughout the year.  Results
		suggest that the relatively high DOC associated with fresh water
		is diluted as fresh water mixes with seawater in the estuary.
			Most of the year nitrate appears to be removed in the 
		estuary, perhaps due to uptake by microorganisms, ammonia
		concentrations, however, show mid estuarine maxima indicating its
		production within the estuary.



							116
			











                     Phosphate concentations in the estuary suggest conservative
                     

                mixing throughout most of the year.    During May and June,

                phosphate appears to be removed in the estuary.  Although

                phosphate concentrations are mostly conservative in the Little

                Manatee estuary, the relative value of the fresh water and high

                salinity end-members varies. January to March fresh water

                concentrations are higher than the high salinity (i.e, ocean

                end-member) concentrations. This is true during July and August

                as well, but during the rest of the year the high salinity mixing

                end member has greater concentrations of phosphate than does the

                fresh water end-member.




                     Total Suspended Sediments and Particulate Nutrients.         Total

                suspended solids increase virtually conservatively from zero to

                higher salinities.    This suggests that the greatest source of

                sediment to the Little Manatee estuary is Tampa Bay.

                     Particulate carbon, nitrogen and phosphorous are

                significantly torrelated (0.01) throughout the estuary,

                throughout the year.     While it is apparent that a large fraction

                of the particulate nutrients is derived from Tampa Bay, there is

                some indication that particle production, due to primary

                production, may influence mid-estuarine concentrations during

                June.











                                                  117















            Chlorophyll, Phytonplankton and Primary Productivity


                 An important component of the Little Manatee River study was

            an investigation of spatial and temporal patterns of primary

            productivity in the estuary.   Water quality parameters related to

            primary production, i.e. nutrients, chlorophyll a and light

            penetration profiles, were measured at each water quality

            station.  In addition, researchers from the University of South

            Florida accompanied field crews on each trip and collected

            surface-water samples for analyses of phytoplankton composition,

            primary production (photosynthesis) and nutrient limitation.   A

            brief summary of the year one results for chlorophyll

            concentrations and phytoplankton abundance and composition is

            presented below. Much greater detail regarding these data, plus

            the results for the primary production and nutrient limitation

            analysis are contained in the report submitted by Dr. Vargo of

            the University of South Florida (Vargo, 1989).

                 Mean annual values for chlorophyll a primary production and

            total phytoplankton cells are listed in Table 26.3. Chlorophyll a

            and phytoplankton cells were measured at all stations, while

            primary production measurements were performed at all stations

            except 6 ppt salinity and Ruskin Inlet.   Because all stations

            except Ruskin Inlet were consistently collected along the

            salinity gradient, the results for Ruskin.Inlet are examined

            separately.







                                           118
















                                -------------------------------- -- ------------------ --------- - --

                                      Table 6.3                           Annual mean values, for several parameters related
                                                                              to primary production in the LMR and Tampa Bay,
                                                                                                      
                                                                             arranged in rank-order.

                                       Total Phytonplankton                                                  Chlorophyll a                                           Primary Production


                                       Rank         Station                    Cells ml                     Station
                                                                                                                                                 ug/l               Station                    mgCm            hr


                                       1          R. Inlet				9391.1				0%						20.3				0%				122.25
                                                      				
	                                    2		  T.Bay			6007.0				R.Inlet					19.3				T.Bay				89.38

                                       3             0% 				4712.1				6%						15.6				12%				84.85				

                                        4          6%					4314.0				12% 						10.2				18%				50.89                                                                                       
                                       
							5         12%				3260.8				T.Bay						9.4

						   6		    18%				2808.8				18%						7.3
		
                                                                                             

                                                                                                                      



                                       -----------------------------------------------------------------




                                                   The ranking of mean values for chlorophyll a, primary

                                       production, and total phytoplankton cells sh the moveable

                                       salinity stations which were located in either the river or boat

                                       Channel outside the river mouth.  All three parameters were                                   

                                       highest at the 0 ppt station, and steadily decreased with 

                                       salinity, being lowerst at the 18 ppt station.  Generally,

                                       variation in these parameters was much greater at the low 

                                       salinity station with frequent high values indicative of 

                                        periodic algae blooms. Near the mouth of the river in higher         

                                       salinty waters, seasonal variations in phytoplankton cells,


                                       chlorophyll a and primary production were much reduced.  A more

                                       detailed discussion of seasonal trends for these parameters is

							presented in a following section.















			The results for the Tampa Bay station showed an inconsistent
		ranking with regard to the moveable salinity stations.  This may
		reflect that the fixed-location bay station was always the most
		seaward, and represented a much different physical environment
		from the moveable stations which were located within or near the 
		mouth of the river.  The bay represents a high salinity (>18
		ppt), wind mixed, open-water environment where substantial
		phytoplankton populations are present year-round and waters are
		generally low in dissolved nutrients, particularly silica and
		nitrogen.  Total phytoplankton cells were highest at the bay
		compared to the other stations except Ruskin Inlet.  Chlorophyll
		concentrations, however, were comparatively low and ranked only
		above the 18 ppt station.  this difference in ranking for
		phytoplankton cells and chlorophyll concentrations is probably
		due to phytoplankton species composition in the bay, which was
		ususally dominated by diatoms with low concentrations of 
		chlorophytes and blue-green algae.  Primary production at this
		site was at a moderate level, similar to the 12 ppt station.

			In sum, although the bay was ranked differently for the
		various parameters, a consistent pattern was observed for the bay
		and river system.  Phytoplankton production was high in the low-
		salinity upper reaches f the estuary ad generally declined,
		with reduced seasonal variations, toward the mouth of the river.	
		Phytoplankton production did increase, however, from the 18ppt
		salinity station to the bay reflecting a transition from the
		river mouth to the open-bay environment.  On some dates, usually

								120




~0
















                                                                                                                                                            ~j


                                                    T ~qi -I ~e   ~qF~.~, ~I..~t ~qk ~qi ~r I   I ~n               ~+~1 ~E~k t: ~qi   r-         h ~C~@     -;I'!        :I:, t ~qV~c, ~-~r   ~qf          ~C~:~1


                                        i ~r~i t h ~e~. ~c~-~;t ud                    ~k~4  ~S I ~-D       a t ~e d i r~j ~c~%~k              I ~i a I-) n     ~qj~.-ed t~r~qi~qL~l~ut~ar-                       t~,~:~-~-~-~,


                                                                                                                                                                                     ~qt I           ~qj. ~V~E
                                        Little ~qlv~ql~an~at~eE~7.~.                    ~j.~-~t p p ~Y~'  ~-x ~qj m a t        ~q3. ~qy   ~'~7   5 ~f ~7 ~1 ~qi ~q1. ~e ~E~-~:~@  ~up~s~itr~e~E~.~-~tm fr~c~.~m                         ~E~.~.~.~.           ~r


                                                                                                                              ~1-~1 ~@~z~:~-~.L
                                        ~f~T~i~,~.~-~.~.~i ~qu t h               ~qk I r~~,    I r ~1~q3.   ~qt ~r          e~l ~V ~C.~?                      d ~c~.~, ~r~- a L~-~, ~q1 e     t ~-~-~. r m w a ~qt~. e r          U n        f


                                        ~a f t ~e~. r r a ~qi n ~s , ~qL~I U t r ~e ~c~S J ~cl ~en c~. e~.~.~- -~I~- i m e ~E-~-~. i n t h ~e I r ~i I e t a ~r e p r ~-~-D b a ~qb 1 y

                                        relatively l~c~-ng b~e~,~-~-~,~7~kL~tSe tidal -~=~ind river ~CUrrent~s appear t~c~, be


                                        M~LAC~-h reduced th~er~E~.~.~.                                                  to t~-h~c~.~, m~o~kin ~ch~ann~C~.~6qA. ~--~-f th~E:~-~.~, ~1-~1~VE~N~1~.


                                        Ph~qvt~o~qpl~an~qkt~on ~c~e-~q11 c~-~D~qunt~s~-~7~. were h~qiQhe~st                                                              for this st~ati~c~-n dU~C~-~1 t~O ~an


                                        ~ab~Uncl~ance of                                                                       ~qA~0qdth~O~L~.~qMh th~e m~c~-~-~-~,~an ~1~'~)~L.~If~f~)~qL~'~1p~2p~p~of


                                        phyt~c~-~6qplan~qkt~c~in cells was twice ~qas great for Ruskin Inlet compared

                                        to t~qf~-~-~j~e C~) ppt                  ~5t at ~qi on ,           t h ~e ~s ~e s t a ~-t ~qi c~. n ~s h a ~C~qJ ~F~, ~qi ~m ~qi I a r                        c h I ~I~:~- r ~-~-~-~, ~qp h ~qy I

                                        m e a n ~s :~, f a p p                    i m a t e 1 y ~q2~-~4qY) U ~q / I




                                                                                                                                  f
                                        ~S~qe~a~sc~qm~a~ql. Tr~qend~c~-: for Chlorophyll ~-~qF.~rn~c~entr~ati~o~n~s and ~qPh~qyt~qo~qp~ql~a~qD~qkt~qon

                                        ~qF~.  m       s J~ t        n            SL~A~rf~a~I-~C~? water                           ~c~i~r ~qop h~,,"Il                                                    for

                                        ~e~S~:~-tL~A~,~R~r~qj~.F~j~E ~st~a~-~1~1~-i~o~n~s: ~ar~e plotted bv d~at~-~E~-~-~.~, in ~-~qF~qi~c~l~u~r~E~:.~, ~qC-~qS.                                                                         ~6q7~1~--~1 e ~F~; ~e

                                                        ~s ~@~- ~-~s-               -a 1 ~qi t ~7~-~t t ~qi v ~e ~q1.        1    m p     ~r e ~qd ~qt~. ~.~-~D p                        A n ~qk t      ~n a b ~L ~i n d ~@~7 ~i        ~c~.~-     ~i
                                                               a        q u ~r


                                        ~S~-~-~, ~qp ~E~- ~I~-~- ~J~. E~l ~E ~C   ~(T~-~1 ~Q ~I~--~, ~E~. ~qi t i ~o n ~-~-~J n t I ~-~i ~e E~, ~F. t ~U ~@~-~.~k ~J~@ V             ~qH    ~w        ~E~n~, ~r     t h ~e, ~)~, ~e p~,~-~, ~r ~qt: ~qL~j y ~'~V~'~-~=~A r ~c~1~c~,


                                                   ~C4                   d i     ~e          r ~-~i ~t ~t I t~. ~c~, ci    ~qf     ~r   ~qj ~e t        I ~E~.~-~.~, d ~qi ~i ~-~i f      f ~-~f  t ~qi ~c r ~-              ~r~- d  ~t~. r ~~i





                                                                                          ~qr ~q1~qC E I I t: r ~qx~qIt~q- ~6qi ~qo n         ~0qJ. ~qn ~q-~q1~q1~q-~qa ~qr~qT      a       ~q@~q-~q-~qk    ~qw ~q(~qz~q? ~qr ~qe ~6q1. ~qr~qo~q@~.~q)                 ~qc~q.   t h~qa ~qn


                                                         ~6q1.      f             t~q.             ~2qi ::~q, ~qC~2q]    T a ~qf~q-~q, ~q@~qj    I-           ~q1~q@ I~q,    ~6q@~qj                    I-          ~qf~qn                       L
                                                                                                                          ~q7~q!  t ~2q1.     _ ~qj           ~2qt~q.~6q1,            ~qj 4


                                               t~q.      ~qI~qD ~qt..~qt ~qr~qi c ~qi ~q;~q-~q-~q.~q. ~qn ~6qt~q. p 1~q-~q-~qit  ~8qr.:~~q, I ~qn I         n   c~ql ~qr c~q, ~qu p     cl ~qi.~q.~qt ~q-~qr~q- ~6qj~q. n   t h ~6qj.            ~6qj.               d     ~qw ~qE~q.~q.~q. ~q-~q1


                                                                                                                          r
                                                 t ~6qi     ~qu ~6q1 a      ~q.~2q1.        1- ~qI~q.~qJ f~q'~qf ~qE'~qr ~qt~qj                        ~q-~q-~q-~q-v     and       F ~qe     ~qi~q@ ~qu ~q:~q:~q4 ~qr             h~qc~q- ~qI~q: ~qi. ~qc~qj h  -~q1    :~q1.
                                                                                                    ~qJ~q.        ~qj ~qc~qm
 







                                        S7A-1
                                              ON,TAMPA BAY

                     .40






                     3D




                   U20




                     10






                     0
                    05DEC87    14MAR88    22JUNBB    30SEP88     OBJAN89    18APR89

                                                 D AT I-





                                         STATION 18 PPT

                    40





                    30




                  __j

                    20





                    10
                     01
                   05DEEC87   14MAR88     22JUN88    30SEP88    08JANB9    ISAPR89

                                                D
                                                  A
                                                 t,

                   z =Station at Tarnpc Bay site


         Figure   6.1g.  Mean values for surface water chlorophyll a concen trations at six
                         stations in the Little Manatee River estuary.






                                                STATION 12 PP-1




                         40




                         30


                      LD
                         201

                         110
                                      zo,

                          0
                       05DECS7      14MARBB     22JUNBS      30SEP88     08JAN89     18APR89

                                                       DATE

                        a =Stction at Tampa Bay site



                                                   STATION 6 PPT

                           40






                           30






                         0
                           20






                           10







                                                                                        IBAPR89
                          05DEC87      14MAR88     22JUNBS     30SEPBB      OBJAN89

                                                            A



               Figure            (Continued)
                                                                         n




                                                       U








                                                 STATION 0 PPT

                          70



                          60



                          50



                     -j 40



                          30



                          20



                          10.



                          01
                          05DEC87  14MAR88      22JUN88      30SEP88      08JAN89      18APR89

                                                       DATE





                                           STATION RUSKIN INLET

                          60



                          50




                          40


                    0 30


                          20


                                                                      M

                          10



                          01.
                     05DEC8?      14MAR@B      22J6NBB      30SEP88      08J'AN89     18APIR89
                                                      DATF

         Figure 6.0-       (Continued)
                                                                     n,
                                                                              n.




		not reflected by the chlorophyll data.  Chlorophyll

		concentrations were at increased levels in the early summer, but

		were low during the September flood.  Peak chlorophyll

		concentrations occurred in late September and early October, when

		the blue-green alga Schizothrix sp. reached high densities.  It

		is believed this blue-green algal bloom was associated with the

		increased nutrients and reduced salinities in the bay following

		the September flood.  Chlorophyll levels returned to low values

		in the following winter period.

			Chlorophyll concentrations were remarkably stable at the 18

		pot station, being less than 10 ug/l except during the Octover

		Schizothrix bloom when this station was located at the Tampa Bay

		site.  With the exception of this bloom, microflagellates and

		diatoms were the dominant phytoplankton groups at this station.

			Chlorophyll concentrations at the 12 ppt station showed a

		steady increase from winter to spring and were maximal in early

		July.  This July peak was due to a bloom of an unknown, naked

		dinoflagellate which burst upon preservation.  Chlorophyll

		concentrations and phytoplankton cells were low during the

		September flood and remained below 10 mg/l for the remainder of

		the study.  After the flood large numbers of the blue-green alga

		Schizothrix were not found at this station as the bloom was

		confined primarily to the waters of the bay.


			The largest spatial differences between chlorophyll

		concentrations occurred between 12 ppt and 6 ppt salinty

		stations.  Chlorophyll concentrations increased at the 6 ppt


					125
		




		station through the spring, and fluctated between 15 and 40 ug/1
		from April through July.  Microflagellates became relatively more
		important as water temperature increased.  Decreases in
		chlorophyll levels and phytoplankton abundance were observed
		during August and September when river flows were at high
		seasonal levels.  It is suggested that low residence times in the
		upper estuary during high flow periods inhibited the development
		of large phytoplankton populations.  Values for both parameters
		increased during October, and showed pronounced short-term
		variations, occasionally reaching high values, during the
		following fall and winter.  Diatoms and microflaellates were the 
		dominant phytoplankton groups at this station with diatoms at
		their greatest abundace during the fall and early winter. Also,
		several typical freshwater species were periodically found at 
		this station.
			Chlorophyll concentrations at the 0 ppt salinity station
		showed large seasonal variations, ranging between 3.1 ug/1 and
		63.8 ug/1.  Chlorophyll concentrations were low in the winter of 
		1988, but increased to values between 15 and 40 ug/1 during April
		through June.  Chlorophyll returned to low values from July 
		through September.  Phytoplankton numbers followed this same
		trend and were low during the winter (January and February) and
		summer, separated by high spring counts.  Although temperature
		effects could have been important for the winter minima, both
		chlorophyll and phytoplankton were clearly lowest at this station
		during periods of moderate to high streamflow, indicating that

							126





	phtonplanktonl populations are flushed from the upper estuary by

	moderate to high flows.  Chlorophyll and phytoplankton both

	showed pronounced peaks when flows returned to normal in October.

	The first peak was dur to a bloom of Skelotemema costatum, a

	ubiquitous estuarine diatom that was distributed throughout the

	river and bay.  The second bloom was comprised of large numbers

	of Cyclotella sp., a species that was restricted to low salinty

	for the remainder of the year with periodic blooms due primarily

	to diatoms or microflagellates.  Freshwater chlorophytes (green

	algae) were most abundant at this station but never averaged more

	than 7 percent of the total phytoplankton cells.  High

	chlorophyll and phytoplankton values at this station were the

	result of rapid algal growth in the estuary, and not imporation

	from upstream, since chlorophyll values at the most downstream

	freshwater stream station averaged 2.7 ug/l and never exceeded

	8.6 ug/l.

		Chlorophyll values at Ruskin Inlet showed a seasonal pattern

	distinct from the other stations.  In contrast to the other sites,

	chlorophyll concentrations were high in the winter of 1988.

	Chlorophyll concentrations remained between 10 and 30 ug/l during

	the summer, generally being the highest values found in the

	estuary during that period.  Peak chlorophyll values occurred in

	November due to a bloom of Skelotemema costatum.  The most

	notable characteristic of the phytoplanton community in Ruskin

	Inlet was the almost continuous presence of chlorophytes,


				127







		paticularly Euglenoid flagellates, and dinoflagellates.








									128

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                                          131