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






                                             CZ-214


                                   Final Report-New Grant Task 2




                                                                   
                                             STUDY OF

                               NON-POINT SOURCE THERMAL POLLUTION

                                              IN


                                         JABEZ BRANCH








                                          Prepared by

                                        KENNETH YETMAN
                       POWER PLANT AND ENVIRONMENTAL REVIEW DIVISION
                                             OF THE
                                   TIDEWATER ADMINISTRATION
                          MARYLAND DEPARTMENT OF NATURAL RESOURCES





                                                                 COASTAL ZONE
                                                             INFORMATION CENTER



                                        February, 1991


           TD
           427
           H4    this work was provided in part by the Coastal Resources Division, Tidewater  
           Y48   on, Maryland Department of Natural Resources through a grant from the
           1991  ean and Coastal Resources Management, National Oceanic and Atomospheric
                 on.
 








                                      STUDY OF

       NON-POINT SOURCE THERMAL POLLUTION

                                              IN


                                 JABEZ BRANCH








                                          Prepared by


                                        KENNETH YETMAN
                       POWER PLANT AND ENVIRONMENTAL REVIEW DIVISION
                                             OF THE
                                   TIDEWATER ADMINISTRATION
                          MARYLAND DEPARTMENT OF NATURAL RESOURCES












                                        February, 1991




       Funding for this work was provided in part by the Coastal Resources Division, Tidewater
       Administration, Maryland Department of Natural Resources through a grant from the
       Office of Ocean and Coastal Resources management, National Oceanic and Atmospheric
       Administration.











                              ACKNOWLEDGMENTS




               several members of the Power Plant and Environmental Review

          Divisions staff assisted in this study. Greg Galbreath and

          Merion Geremia helped gather and manage the large volume of field

          data collected. Kate Meade assembled the information on land use

          and Dr. William Hodges provided valuable assistance and guidance

          throughout this study.



               The Coastal Resource Division, Tidewater Administration,

          Maryland Department of Natural Resources provided funding to

          support this work through a grant from the Office of Ocean and

          Coastal Resource Management, National Oceanic and Atmospheric

          Administration. Funding and assistance were also provided by the

          Maryland State-Highway Administration.









                                Executive Summary


0


                in 1990, the Maryland Department of Natural Resources began

           a monitoring study of non-point source thermal pollution in Jabez

           Branch. Jabez Branch was unique because it was the only stream

           in the Maryland Coastal Plain which supported a natural

           reproducing trout population. Highway construction and land use

           changes in the stream's watershed have altered drainage patterns

           and today trout are no longer present in the stream. The primary

           objective of the present investigation is to identify the

           potential sources of non-point thermal pollution affecting the

           upper portion of Jabez Branch where trout once existed. This is

           being done by studying the spatial and temporal patterns in which

           thermal pollution occurs within the catchment during a variety of

           summer rain storm events. Field monitoring in the first year has

           concentrated on collecting baseline information on stream flows,

           water temperature, rainfall and land use.



               Results from the 1990 land use surveys indicate that nearly

           50% of the left fork watershed of Jabez Branch remains forested

           and much of the remaining land is in agricultural use. It is

           estimated that at present less than 4 % of the left fork

           watershed is covered with impervious surfaces. Despite the









           fairly-low level of urban development, results indicate that

           runoff generated within the watershed increases stream water

           temperature near the tolerance limit of brook trout.



                The relatively large rises in stream water temperatures

           appear to-be the result of two factors. First, the left fork of

           Jabez Branch is a small stream with a summer base flow of only

           0.3 cfs. Because normal base flow in the stream is low, even a

           small amount of warm surface runoff can have a dramatic impact on

           stream water temperature. The second factor is that development

           in the left fork watershed is concentrated in the upper sections

           of the,drainage basin. When it rains, runoff from commercial,

           residential and agriculture land in the upper watershed

           concentrates in drainage channels and quickly flows down stream.

           This runoff has not only been heated from contact with roads and

           other warm surfaces, but the volume of water originating from the

           upper watershed is relatively large. As this heated runoff moves

           down stream, it changes water temperature along the entire length

           of the left fork of Jabez Branch.



                The largest rise in water temperature in the lower left fork

           of Jabez Branch during 1990 occurred on July 12 during a 2.65

           inch rain event that occurred in the late afternoon (18:30) on a

           fairly warm day (31.70C or 89.10F). Water temperature on the

           left fork rose from 170C (62.60F) to 23.90C (750F) as stream

           flows increased from 0.3 cfs to 17.5 cfs. Monitoring of runoff

           within the left fork watershed found that the runoff from a road









           was 280C (82.40F) at the beginning of the storm and the

           temperature of the runoff from an industrial roof was 24.50C

           (77.90F). In the more urbanized portions of the watershed, the

           temperature of the runoff was initially above 270C (80.60F) and

           then dropped to just below 250C (770F) during the storm. Runoff

           primarily from agriculture land was around 230C (73.40F) at the

           start of the storm and rose during the rain event to 250C (770F).

           During the July 12 rain storm, the temperature of the surface

           runoff from a forested subdrainage basin remained fairly constant

           at around 220C (71.60F).



                one surprising finding in 1990 was the relatively low pH in

           the center portion of the left fork of Jabez Branch. During base

           flow conditions the pH in the mid-section of the stream was 5.2.

           Water at this pH is considered to be fairly acidic and can be

           stressful to many aquatic organisms. In addition to pH levels

           varying along the stream's length, pH also fluctuated when it

           rained. continuous monitoring of pH near the mouths of the left

           and right forks indicates the pH of the stream can drop as much

           as 1 pH unit shortly after the beginning of a rain event.












                                  INTRODUCTION



                Before settlers came to this country, forests dominated the

           eastern seaboard. In these precolonial times, it is believed

           that most streams in Maryland above the fall line and some

           streams below the fall line, such as Severn Run, supported

           natural reproducing brook trout populations. As forests were cut

           down, fl ow patterns in Maryland streams changed and many streams

           became degraded, losing their ability to support trout (Barry,

           1958; Powell, 1967). Trout are very sensitive to changes in

           water quality especially increases in water temperature. When

           present, trout are generally an indicator of a healthy cold water

           stream system.



               While the general causes for the historical decline of trout

           and other aquatic resources in Maryland are known, little

           information on the specific impact that land use changes have had

           on aquatic systems is available. Questions on how much

           development can occur in a watershed before a fish population is

           affected or how much a specific land use change could raise water

           temperatures in a stream can not be answered at this time.

           certainly, if Maryland is to protect its remaining healthy

           streams and possibly restore other degraded waters, we must have








           a better basic understanding of the cumulative effects that land

           use changes have on the State's streams.



                Jabez Branch is a tributary to Severn Run in Anne Arundel

           County, Maryland (Figure 1). The stream was unique because it

           was the'only remaining stream in Maryland's Coastal Plain which

           supported a natural reproducing trout population. In 1987,

           however, field surveys by the Maryland Department of Natural

           Resources (DNR) found that a severe decline in the trout

           population had occurred, and the most recent surveys done in

           December, 1990 indicate that brook trout are no longer present in

           Jabez Branch. The initial decline of brook trout in Jabez Branch

           is believed to be linked to highway construction which altered

           drainage patterns and created a new warm water discharge to the

           stream. Corrective action was taken to eliminate the warm water

           discharge created by highway construction; however, storm water

           temperature monitoring and fish surveys indicate that non-point

           source thermal pollution remains a problem in the stream.



                An field monitoring study began in 1990 to examine non-point

           source thermal pollution problems on Jabez Branch. For the most

           part, non-point source thermal pollution only occurs when it

           rains. Since rain storms are both episodic and variable in size,

           monitoring must be done over several years so that a wide range

           of possible environmental conditions can be seen. This report is

           a presentation of the results from the first summer.'s monitoring.





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                         Jabez
                    3    Branch                                                             Severn
                                                                                             River
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                    -Poll'
                fork                                                 ANNE
                    lef t,                     119                 ARUNDEL
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                                 Lake
                                 edian


                                                                     BY JOSE ARAWO FOR THE WASHING70N POST



0

              Figure 1. Map showing location of Jabez Branch. (Origional figure from
                         March 27, 1989 Washington Post)


0








                The present investigation of Jabez Branch repr esents a

           unique opportunity to document a trout stream at the critical

           turning point in' its ability to support a trout population.

           Hopefully, once the non-point source pollution problems on Jabez

           Branch are better understood, the actions needed to restore this

           unique natural resource will also be clearer.



                The primary objective of this investigation is to identify         14

           the potential sources of non-point thermal pollution affecting

           the upper portion of Jabez Branch where trout once existed. This

           is being done by studying the spatial and temporal patterns in

           which thermal pollution occurs within the catchment during a

           variety of summer rain storm events.










                         BACKGROUND INFORMATION



0

           MARYLAND TROUT STREAMS AND JABEZ BRANCH



0              Brook trout were first discovered in Jabez Branch in October

           1977. At that time, it was believed that trout were present only

           upstream of Maryland Route 32 (Figure 2). Since the initial

           discovery, DNR biologists have conducted periodic electrofishing

           surveys of the stream. Data from these surveys are shown in

           Table 1. The earliest extensive survey of Jabez Branch, in 1986,

           showed that in addition to the brook trout present above Rt. 32,

           brook trout were also present downstream. Trout were collected

           in the mainstem of Jabez Branch both above and below Hog Farm

           Road and in the Hog Farm Road tributary. The 1986 survey also

           indicated that the highest density of brook trout in Jabez Branch

           occurred in the stream's.upper left fork. The success of trout

           in the left fork is believed to be due to the large amount of

           spring water that flows into this segment of the stream.



0             In September 1987, routine surveys by the Department's

           Freshwater Fisheries Program discovered that a severe decline in

           the Jabez Branch trout population had occurred (Table,l).

           Further investigation revealed that construction of 1-97 had












                    Table 1. Number of brook trout collected in Jabez Branch.






                                                              1977          igao          1983          1986                   1987                 1988         1989           1990
                                            Distance        Oct. &          June          Nov.         Nov. &       Aug. thru       Dec.               &        Dec. &          Dec.
                                            Surveyed          Nov.                                      Dec.         Oct.                        Jan. 1989     Jan. 1990
                                            (yards)

                       Left Fork             unknown                       common
                                               164             6
                                               175                                          8
                                               350                                                        24
                                               383                                                                       1             0             0              0             0

                                                        I
                       Right Fork         ..Izl,350                                                        11
                                               631                                                                       3             1
                                               333                                                                                                   4              2             0

                       Upper Mainstem          100                                                          3
                        (Rt. 32 to             219             0
                        Hog Farn d             631                                                                       2                           0              0             0

                       Lower  Mainstem         100
                        (Hog  Farm Rd.       z133
                        to Severn Run)         200
                                               433                                                          0
                                            2,233                                                                        7                             1            0             0

                       Hog Farm Rd.            200                                                          2
                        Tributary            =587                                                                                      0
                                             =633                                                                        0                           0              0             0

                       Gambrill Rd.            250                                                                                     0
                        Tributary            =800                                                                        0

                       Warfield                200                                                          0
                        Tributary







                                   ROO I                 J00 I
                                                           RT
                                                           32
                                            LOO I

0                                                     L002

                                               L003



                                          Ll 10
                                        L 109
                                      L104                      LAKE MEDIAN
                                                         -WEATHER STATION
                            L103                      -RoadTe
                                                     -H001
                    L102                             L 106         RT 175

                                                     RooF01
                                                  --L 105

                                        L107


                                   L ib I

                                RT
                                 3







        Figure 2. Map showing location of sampling station in upper Jabez Branch
                  watershed in 1990.









           created a new retention basin which was discharging heated water

           into the left fork of Jabez Branch. The State Highway

           Administration was notified and the discharge was eliminated in

           the spring of 1988.



                Following the discovery of the decline of trout in Jabez

           Branch, a second fish survey was done in December, 1987 to obtain

           seasonal data comparable to the survey done in 1986. Results of

           the second survey confirmed that few trout remained in the stream

           (Table 1).



                In 1988, two continuous recording thermographs were placed

           in Jabez Branch to monitor summer water temperatures. Results

           indicated that water temperatures, both in the left fork and in

           the stream's mainstem, experienced several sharp temperature

           rises. Further analysis of this data in combination with

           rainfall data collected at BWI airport located 7.5 miles north of

           Jabez Branch, indicated that sharp temperature rises in the

           stream corresponded to local rain events. For example, on August

           29, 1988 water temperature in the left fork rose from 17.50C to

           230C within a sixty minute period following a one-inch rainfall.

           Temperature rises such as these are a major concern not only

           because the high temperatures may exceed the upper tolerance

           limit of brook trout, but also because very rapid changes in

           water temperature can be extremely stressful to the entire

           aquatic ecosystem.








                Winter fish surveys of Jabez Branch have continued since the

           initial decline in the trout population was discovered. In the

           three years since 1987, one-pass electrofishing surveys were done

           in all areas where brook trout had previously been collected, or

           in areas where trout were suspected to be present. Results

           indicate that a steady decline in the trout population has

           continued (Table 1). In 1988, electrofish surveys of Jabez

           Branch collected only 5 brook.trout (four young-of-the-year and

           one adult), and in 1989, only 2 yearling brook trout were found.

           The most recent survey was completed in December, 1990, and was

           unable to find any brook trout anywhere within the stream. It is

           now believed that a brook trout population no longer exists in

           Jabez Branch.




               Past surveys of Jabez Branch indicated that the highest

           standing crops of brook trout in Jabez Branch have traditionally

           occurred in the left fork. The left fork has also been observed

           to have the greatest spring water influence. It is the opinion

           of the Maryland Freshwater Fisheries staff that the repopulation

           of brook trout into the left fork is essential for the

           restoration of a natural reproducing trout population in Jabez

           Branch (Bachman, personal communication). The reason for the

           failure of brook trout to repopulate the left fork is not known

           at present. It is suspected, however, that high and rapid water

           temperature changes may have prevented brook trout from

           reestablishing themselves in this area. Repopulation of brook

           trout into the left fork may also be affected by the scarcity of








           fish in the system. After the initial decline of trout in Jabez

           Branch in 1987, there may have been too few individuals left in

           the system to sustain a reproducing population. Now that it is

           known that no native brook trout are left in Jabez Branch, the

           Freshwater Fisheries Program of DNR is preparing a restocking

           plan for the stream.






           EFFECTS OF URBANIZATION



                The'effect:ï¿½ of urbanization on a catchment and drainage

           system are numerous, particularly in terms of hydrology and

           microclimatology. The following discussion is provided as an

           overview and pertains primarily to those impacts which affect

           runoff and heat transfer processes.



                In a mature forest, rain is intercepted and stored by the

           tree canopy until the storage capacity is exceeded. Once rain

           reaches the surface, it is held in the humus.layer which aids in

           infiltration of rain water into the underlying soil. Runoff in a

           mature forest rarely occurs at the surface as overland flow.

           Instead, water moves laterally as throughtlow within the soil

           until it is discharged as base flow or delayed storm flow through

           a stream bank. Typically, any overland flow component of runoff

           is limited to areas adjacent to existing channels which have

           become saturated by subsurface drainage or runoff; therefore,








           true surface runoff occurs primarily after soil storage is

           exceeded by drainage saturation.



               As forests are cut down, they are replaced by impervious

           surfaces (e.g., roads and parking lots) or by surfaces which are

           greatly'altered (e.g. farm fields and lawns). Surface hydrology

           changes accordingly and affects a catchment's response to

           rainfall events. The changes in land use have pronounced effects

           on the mechanisms which regulate runoff generation.



               Generally, surface changes due to urbanization reduce

           infiltration, and the amount of rainfall which becomes surface

           runoff increases. Additional effects include a reduction in

           depression storage (i.e., water held in surface depressions) and

           an increase in overland flow velocities. The result is an

           acceleration of hydrological processes which produces a flashier

           runoff regime with higher peaks developed more rapidly and with

           shorter lag times.



               Surface modifications influence the amount of water and the

           timing of runoff reaching a stream; however, the extent to which

           these changes have a measurable impact on hydrological processes

           is governed (at least in part) by the magnitude, frequency and

           duration of rain storm events. Flood peaks increase relative to

           their respective return periods, but extreme events within

           urbanized areas barely increase over those which occur in

           undeveloped watersheds. The reason is simple: during high









           magnitude (or extended duration) storms the catchment becomes

           fully saturated with maximally extended networks so that the

           hydrological response of a rural watershed replicates that of an

           urban basin (Richards, 1982). In effect, hydrological impacts

           associated with urbanization are most pronounced during storms of

           intermediate magnitude.



                Surface alterations due to urbanization also affect the

           microclimatology of an area largely through changes that

           influence heating of a surface and transfer of heat to air or

           water. In this case, shade is a primary factor, and reductions

           in shading increase the amount of solar radiation reaching the

           surface. As shading is reduced due to surface changes, the

           reflectance (albedo) of an area is altered. In general terms,

           the reflectance of a surface is a relative indicator of surface

           heating. A surface with a high reflectance tends to heat less

           rapidly and less intensely than a surface with a low reflectance.





                As rain falls in an urbanized environment, the runoff

           produced on a surface is heated more rapidly and to a higher

           temperature than runoff generated within a forested environment.

           The runoff can be very warm especially if it originated on'a road

           surface or a parking lot which has been heated by the sun just

           prior to a rain event.



               Another effect of urbanization is on ground water. Water








          that previously infiltrated into the ground is now flowing

          overland. This results in a reduction of ground water recharge

          which can lead to a decline in the water table or dewatering of a

          perched water zone. Under these circumstances springs can dry up

          and base flow discharge to a stream can be reduced drastically.

          In some-headwater areas the stream may become completely dry

          except when it rains. As base flow is reduced, the temperature

          of stream flow will rise. This puts additional stress on cold

          water organisms like trout, and if the water temperature rises

          high enough, the stream will no longer be able to support trout.











                                     METHODS


0         SAM PLIN-G. STATIONS


               Non-point thermal pollution problems have already been
411       documented in the left fork of Jabez Branch (Figure 1) and this

          watershed was the focus of monitoring efforts in 1990. Field

          monitoring in the first year has concentrated on collecting
0         baseline information on stream flows, water temperature, rainfall

          and land use.



40             A total of 18 monitoring stations were established in 1990

          (Figure 2). A list of the sampling stations along with a

          description of their location, parameters measured, sampling
0         period and sampling frequency is presented in Table 2. The

          sampling stations fall into 4 groups:



             Meteorological Station



               A automated weather station was established in the upper
0              left fork watershed near Lake Median between the north and

               south-bound lanes of Rt. 3. Air temperature, humidity,

               solar radiation, and rainfall were recorded every 7.282
0              minutes using a Datalynx data logger.   Fluctuations in




0








              Table 2. Name and location of sampling stations in Jabez Branch watershed in 1990 along
                            with information on parameters measured, sampling period at each station and
                            recording frequency.



              Station             Location                        Parameters Measured                 sampling ieriod       Recording
               name                                                                                                         frequency
              -----------------------------------------------------------------------------------------------------------


              Weather       South end of lake Median        Air temp., rainfall, humidity,           6/5/90 to on going       '7 min.
                                                           solar radiation, and lake level


              J002          Mainstem of Jabez Br.           Water temp.                              6/5/90 to 10/9/90         5 min.
                            =600 ft. upstream of
                            Hog Farm Rd.                                                               -


              R001          Right fork of Jabez Br.         Water temp., conductivity,              6/15/90 to 10/2/90        10 min.
                            =800 ft. above Rt. 32           pH, dissolved oxygen                                              or less
                            culvert


              L001          Left fork of Jabez Br.          Flow, water temp. conductivity,         6/15/90 to 10/2/90        10 min.
                            =200 ft. above Rt. 32           pH, dissolved oxygen                                              or less
                            culvert


              L002          Left fork of Jabez Br.          Water temp.                             6/11/90 to 9/24/90         5 min.
                            =650 ft. above Rt. 32
                            culvert


              L003          Left fork of Jabez Br.          Water temp.                             6/11/90 to 10/9/90         5 min.
                            =1200 ft. above Rt. 32
                            culvert


              L110          Unnamed intermittent            Water temp.                              6/7/90 to 10/9/90         5 min.
                            tributary
                            =25 ft. from stream mouth


              L109          Top of cement channel           Water temp., peak water levels           6/5/90 to 10/8/90         5 min.
                            near Charles Hall Rd.


              L107          Rt. 3 south culvert             Water temp.                             6/18/90 to 10/8/90         5 min.
                            near Suburban Propane








             L106         Rt. 3 north culvert            Water temp.                            6/7/90 to 10/8/90        5 min.
                          near Maryland muffler

             L105         Millersville Rd culvert        Water temp.                           6/18/90 to 7/12/90        5 min.
                          at Hansel Dr. intersection


             L104         Sir Walter Dr. culvert         Water temp.                            6/7/90 to 6/20/90        5 min.

             L103         Rt. 175 culvert                Water temp.                            6/7/90 to 10/8/90        5 min.

             L102         McKnew Rd. culvert             Water temp.                            6/5/90 to 9/17/90        5 min.

             LIOI         Rt. 3 north culvert near       Water temp.                            6/5/90 to 10/8/90        5 min.
                          "Bull Shed" restaurant


             Roadte       Asphalt along Rt. 3 south      Road temp.                             6/7/90 to 10/8/90        5 min.
                          near Charles Hall Rd.


             H001         Runoff from Rt. 3 south        Water temp.                            6/7/90 to 10/8/90        5 min.
                          near Charles Hall Rd.


             RoofOl       Down spout drain at            Water temp.                            7/12/90 to 10/8/90       5 min.
                          Maryland Mustang









                water levels in Lake median were also monitored using a

                pressure sensor deployed in the lake. Rainfall was measured

                using a tipping bucket rain gauge which recorded rainfall in

                0.01 inch intervals. In addition to the continuous

                monitoring equipment, a backup cumulative rain gauge that

                measured total rainfall was at the site and a staff gauge

                was deployed in Lake Median. Routine readings were taken

                from both the backup cumulative rain gauge and staff gauge

                along with measurements of air temperature and humidity

                using a sling psychrometer. Field measurements wer e

                compared to data from the automatic monitoring equipment to

                verify accuracy.



              Perennial Stream Stations




                A total of five perennial stream stations were established

                in 1990: three stations were along the left fork of Jabez

                Branch (Station L001, L002 & L003); one station was on the

                right fork (Station R001) and one station was on the

                mainstem of Jabez Branch (Station J002) downstream of the

                confluence of the left and right forks (Figure 2). Water

                temperatures were measured at 5 or 10 minute intervals at

                all stations using either a Ryan Tempmentor or Hydrolab

                DataSonde-l. In addition, conductivity, pH and dissolved

                oxygen levels were measured at 10 minute intervals with the

                Hydrolab DataSondes at Stations L001 and R001. Stream

                discharge data for the left fork of Jabez Branch were









                recorded at 5 minute intervals at a gauging station

                established at Station L001 by the U.S. Geological Survey.

                Weekly measurements of water temperature and other water

                quality variables were made at the perennial stream

                stations to verify the accuracy of the measurements made by

                the continuous monitoring equipment.



             Intermittent Channel Stations



                At the beginning of the study, the upper watershed of the

                left fork of Jabez Branch was divided into 11 subdrainage

                basins. A photomap showing the subdrainage areas is

                presented in Figure 3. Once the drainage patterns in the

                upper watershed of the left fork were known, sampling

                stations were established at points where the runoff from

                one or more subdrainage areas concentrated. In most cases,

                the temperature probes were located in intermittent channels

                either above or below road crossings. The probes were

                suspended on a stick just above the bottom of the

                intermittent channel and measurements were taken at 5 minute

                intervals using Ryan Tempmentors. Due to equipment and time

                constraints, monitoring stations were not established in all

                11 subdrainage basins (Table 2). Priority in establishing

                and maintaining stations was given to sites that drained an

                area dominated by a single land use type.





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                                                                        ............











                                                      Figure 3. MIPS photomap showing the 11 subdrainage areas in the upper left fork
                                                                                                         of Jabez Branch.









              Special Land Use Stations



                Temperatures were monitored at 2 special land use sites in

                1990. At the first site, a temperature probe was embedded

                into the asphalt along south bound Rt. 3 to monitor the

                temperature of the highway's surface (Station RoadTe). A

                second temperature monitor was also deployed at the site and
                was\designed to record the temperature of the runoff

                diverted from the highway. This was done by channeling some

                of the highway runoff to a probe that was suspended just

                above the highway surface. The second special land use site

                measured the temperature of the runoff from the roof of an

                industrial building in the watershed. The temperature probe

                was located at the bottom of one of the roof gutter's down

                spouts. Temperature measurements at all special land use

                sites were made at 5 minute intervals using Ryan

                tempmentors.



          Stream Profile Survey



                In addition to the 18 stations in which continuous

          monitoring equipment was deployed, a stream profile survey of the

          left fork of Jabez Branch was done on June 28, 1990. Water

          temperature, flow velocity, pH and conductivity measurements were

          done along every 100 feet of stream channel starting at the mouth

          of the stream.














           Land Use Estimate's



               Land use in the upper watershed of the left fork of Jabez

           Branch was determined from photographs taken during a low

           altitude aerial survey done on February 13, 1990. Photographs
           were scanned into the Department's "Map and Image Processing            01

           System" (MIPS). The MIPS 'raster images were then registered and

           a second registered vector file of the 11 subdrainage basins was

           overlaid onto the original raster images. Land use in each

           subdrainage basin was then determined using the planimeter

           function in MIPS. In addition to estimating the land use areas,

           the MIPS planimeter was used to estimate the total amount of

           impervious area in each basin. A MIPS photomap showing one of

           the delineated subdrainage basins is presented in Figure 4.











                    1E. @3


                                                                         Av

                 481:1-,










               W!



                                                            %
                                        .VA



                     39,













                                                                    n@ "W':1
0











                                                                         IAM
                                                            :7-


                                                           At-



      Figure 4. Enlargement of subdrainage area VI. The MIPS enlargement was produce
                from a low altitude aerial photograph taken on February 13, 1990.











                                       Results



           Land Use-



                 Land use in the left fork watershed of Jabez Branch was

           divided into 6 categories (ie., agriculture, forest, lightly

           forested, residential, commercial and highways). Result of land

           use surveys are shown in Table 3.



              A total of 597 acres (0.93 sq. miles) are present in the left

           fork watershed. In 1990, approximately half (48 %) of this land

           was forested or lightly forested. The majority of the forested

           land was located in the lower or northern portion of the

           watershed (Figure 3, Subdrainage Basins IV, VIII, IX, X & XI).

           The remaining land in the watershed of the left fork was used for

           agriculture (27.7    or was either residentially (18.3 %) or

           commercially (3.0    developed. The agriculture, residential and

           commercially developed lands were located in the upper or

           southern portion of the watershed (Figure 3, Subdrainage Basins

           I, ii, III, V, VI & VII).



               In general, when it rains in the left fork watershed, runoff

           from agricultural fields, residential neighborhoods and

           commercial lots in the upper portion of the basin will flow into











         Table 3. Estimates of land use (acres) in the watershed of the left fork of,Jabez Branch.




         Sub-basin               I       II      III      IV        V        VI     VII       VIII     Ix        x       xi
         (Station             (LI01) (LI02) (L103) (L104)         (L105) (L106) (L107)               (L109) (LI10) (LO01)        Total
         -------------------------------------------------------------------------------------------------------------------


         Agriculture            14.7    55.3     14.3     9.2       69.6     1.0       0          0      0       1.1      0      165.2


         Forest                 15.0    39.0     7.9      48.0      9.8      6.9      9.3      25.6    2.9      27.1     71.0    262.5


         Lightly
            Forested            3.4      3.9     0        0.4       7.8      0.8      5.0         0    0.1       0       2.5      23.9

         Residential            5.9      16.4   19.4      0.5       50.0     7.6       0        3.0    1.8       0       4.9     109.1

         Commercial              0       9.9     2.2       0        2.5      1.4      1.8         0      0       0        0       17.8

         Highway                3.7      0.5     5.1      2.0       2.1      1.7      1.4       0.2      0       0       1.9      18.6




         -------------------------------------------------------------------------------------------------------------------
         Total area             42.7    125.0   48.9      60.1    141.8,     19.4     17.5     28.8    4.8      28.2     80.3    596.9


         Estimated
          impervious area       3.0      6.5     1.6      0.4       3.7      2.1      1.0       1.4    0.1       0       2.3      22.1


         Percent
          impervious area       7.0%     5.2%    3.3%     0.7%      2.6%     10.8%    5.7%      4.9%   0.2%      0%      2.9%      3.7%










      91            1,          1,            @, k                                    -








           drainage channels and move down into a wide intermittent stream

           channel. The channel conveys intermittent flow for approximately

           2000 ft. until the runoff reaches the headwaters of the perennial

           flowing portion of the stream. The left fork of Jabez Branch

           continues another 2500 ft. before joining with the right fork.



               Land use in each of the 11 subdrainage basins is shown in

           Table 3 along with an estimate of the amount of impervious area

           present. Of the 11 sections examined, Subdrainage Basin VI is

           the most urbanized with 46% of the land in either residential or

           commercial use. The least disturbed subdrainage basin is X which

           is 96% forested. Subdrainage Basins II and V have the largest

           amount of agricultural land. The agricultural land in

           Subdrainage,Basin II is owned by the U.S. Naval Academy's Dairy

           and in 1990 was used to grow 4 grain crop in the spring and corn

           during the late summer and early fall.





           Base Flow Conditions




               Stream flow in the left fork of Jabez Branch has been

           monitored continuously for over a year by the U.S. Geological

           Survey. The USGS gauging station is located at Station L001

           which is approximately 200 ft. above the confluence with the

           right fork. During the summer, base flow at Station L001 was

           around 0.3 cfs. In addition to the USGS gauging station at









           Station L001, a Hydrolab Datasonde-1 was also deployed to monitor

           temperature, conductivity, pH and dissolved oxygen levels in the

           stream. Measurements of most parameters were taken every 10

           minutes. Results from summer monitoring indicated that during

           fair-weather conditions, base flow water temperatures in the

           lower left fork of Jabez Branch varied from 150C (590F) at night

           to as high as 180C (64.40F) at mid-day on very hot days when air

           temperatures exceeded 320C (89-60F). Conductivity and pH at

           Station L001 remained fairly constant at 5.5 and 70 gmhos/cm

           respectively. Dissolved oxygen levels were monitored only from

           June 15 to 21. During this time period dissolved oxygen levels

           ranged from 8.5 to 9.6 mg/l.



                A Hydrolab Datasonde-I was also deployed in the right fork

           of Jabez Branch approximately 300 ft. above the confluence of the

           two forks. All base flow water quality values were approximately

           the same as those recorded on the left fork except for

           temperature which tended to be 20C (3.60F) above the left fork.



                On June 28, 1990, a base flow stream profile survey of the

           left fork of Jabez Branch was done. Temperature, stream flow, pH

           and conductivity were measured at 100 feet intervals along the

           entire length of the perennial reach of the stream. Results of

           the survey are shown in Figure 5. Starting at the stream's

           headwaters, discharge increased steadily-in the upper portion of

           the left fork to approximately 0.2 cfs within 1000 ft of the

           stream's mouth. Stream flow measurements then fluctuated around





                             Left Fork of Jabez        Branch
                                       June 28, 1990
              7-                                                               100

                A-A
           6.5-                        ............... . .. . . ... ............................ ...................... . .. ... . ... . .................... ...........  ............ @90
                                                             pH.,k-.Ac-A   A         E
              6-


                                                                                     >
       CL
                                                                                     S
           5.5-

                                                         Conductivity
                                                                                     0
             5--                                                               60


           4.5- -                                                              50
           0.5-                                                                30

                                                                              -28

           0.4-                                                         _____26

                                                                              -24   0

                                                                               22
      4
                                             Flow                             -20
                                                                                    W
       0   0.2-                                                               __18  CL
                                                                                    E
                                                                               16
                               -Temperature

                                                                              -12

             0-                                                               -10
              1800 1600    1400'1 2'oo'l 6oo'   860   6 60   40'0  20'0    0
                 1700 1500 1300 1100 900 700 500 300 100
                                 Distanch from mouth (ft.)



      Figure 5. Results of stream profile survey of the left fork of Jabez Branch done on
                June 28, 1990.









           0.2 cfs in the stream's lower section until just before merging

           with the right fork where it rose to 0.3 cfs. Temperature

           remained fairly'constant around 160C (60.80F), and conductivity

           varied between 70 and 82 gmhos/cm in the upper portion of the

           stream and then remained fairly constant at 70 gmhos/cm down

           stream.- The pH of the water in the left fork was 6.6 in the

           headwater of the stream, but dropped to 5.2 at approximately 1500

           feet above the stream's mouth. The pH of the stream then rose

           steadily to 6.3 just before the channel merges with the right

           fork.






           Summer Storm Events



                Between June 1 and September 30, a total of 29 precipitation
           events were recorded at the weather station in the upper Jabez

           Branch watershed. (Figures 6 through 9). Seventeen of these

           events were small, resulting in less than 0.25 inches of

           precipitation. Results from Station L001 near the mouth of the

           left fork showed no changes in either stream flow or water

           temperature following these small rain events. Of the remaining

           12 rain events, 7 produced between 0.25 and 1.0 inches of rain, 4

           produced 1 to 2 inches of rain and 1 large rain event produced

           over 2.65 inches of rain.



                Changes in stream flow and water temperature in Jabez Branch



                                             June
               201
               18-11                      Stream Flows
               161
               1 4j-
               12,
           3:  10
                8
                6-1
                4]
                2.

                0
                3-

                                              Rainfa-il
                   - - --- - - --------- . . ...............
               2.5                                  ............. .....



                2  ................ .


          C
               1.5 ................................... .. . .. . ............ . . ... . . ...




                   - - - ------------------ -
          cc






                01
                                          1'1 1'3  15 17     19 21 23 25 27 29
                   1   3 5
                    2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
                                                   Date


       Figure 6. Graphs of stream flow (top) at Station L001 on the left fork of Jabez
                   Branch and total daily rainfall (bottom) at the Lake Median weather
                   station during June, 1990.




                                                  July
                 20
                                                  Stream Flows

                 16

                 14-

                 12---

                 1U-

                 8-

                 6-

                 4-

                 .2 . ....... --------- ----

                 07
                 3"
                                                       Rainfall
                2.5-












                0.5-


                 Oi
                            5    7 9 1'1               17 1.9 21 '@3'@5 27 29 31
                     2 4      6 8 10 12 14 16 18 20 22 24 26 28 30
                                                   Date@
        Figure 7. Graphs of stream flow (top) at Station L001 on the left fork of Jabez
                   Branch and total daily rainfall (bottom) at the Lake Median weather
                   station during July, 1990.




                                             August
               20

               18-
                                           Stream Flows

               1

               1





                6



                2

                01     1 i I
                3-

                                                Rainfall
               2.5-                                                            . .....


                2-                                             . .. . . . ......

          U





          C

         a:





                0 -                                                      Ale
                  1   3 5 7 9 11 13 15 1'7 1119 1 21 23 25 27 29 31
                    2 4 6 8 10 12 14 16 18 20 92 24 26 28. 30
                                                  Date


        Figure 8. Graphs of stream flow (top) at Station L001 on the left fork of Jabez
                  Branch and total daily rainfall (bottom) at the Lake Median weather
                  station during August, 1990.
                              Li




                                          September
                20-


                                            Stream Flows

                14-

            Cn% 12-

                1 U-

           0
                 8-

                 6-

                 4---

                 2

                 0-
                 3-
                                                 Rainfall

                                                                   . . ........ . ........ ........... ....... . .. . . ..... . ....





          Cn
                             - - - - -- - ---- -------- . ...... .. ....... - - -- - ------






                                                                                ..............






                   . .. . . ............ . ...........











                 0-
                   1   3 5 7 9            11 13 15 17 19 21 23 25 27 29
                     2 4 6 8 10 12 14 16 18 20 22 24 26 28 30
                                                   Date


        Figure 9. Graphs of stream flow (top) at Station L001 on the left fork of Jabez
                   Branch and total daily rainfall (bottom) at the Lake Median weather
                   station during September, 1990.








          varied depending on the size of the rain event. The results of

          runoff and stream monitoring from three different size rain

          events.in 1990 will be discussed in the following sections.   The

          first rain event was the largest and produced 2.65 inches of  rain

          on July 12 and 13. The second rain event occurred on August   5 &

          6, and was a moderate size event producing 1.37 inches of rain.

          The third was a slightly small rain event which produced 1.14

          inches of rain on September 16.





          July 12 & 13, 1990 (2.65 inches of rain)



               On July 12, 1990, it began to rain at approximately 18:30.

          The exact time of the beginning of the rain event is not known

          because of problems with the tipping bucket rain gauge at the

          weather station on Jabez Branch. The amount of rain recorded by

          the tipping bucket rain gauge (Figure 10) was about half of that

          reported at BWI airport and at the backup rain gauge that was

          also located at the Jabez Branch weather station site. It was

          later discovered that the funnel on the top of the tipping bucket

          rain gauge was clogged and responsible for the faulty readings.

          Nonetheless, we do know that the greatest amount of precipitation

          occurred in the first few hours of the storm, and data from the

          backup rain gauge suggest that the rainfall pattern recorded at

          BWI Airport is a close approximation of that which occurred in

          the upper Jabez Branch watershed on July 12.





                                   July 12 and 13,1990

             35-                                                                 100

                                                                                -95
                                                  Humidity
                                                                                -90
                                                 ...................... ............... .......... . ...............
             30-el

                            I
                                                                                -85
                                                                                       01
                                                                                -80
                                        lip
                                      ....... .  ............        . . . ......... ............ ...............
                                        ... . ......
             25-
         E                                                                      -75
                                                                                       E
                                                                                -70
                                                                           re
             20---                                         Air Temperatu
                                                                                  65

                                                                                -60
             1.5
              3-
                                    Total Rain Gau     e
                                                     9


                                       . .... .. ...
                                                                  E3WI Airport
                                                t
         Cn
           1  2-



         Cz


         Cz                       . . . .......... . ..                n     - - - -------
                                                       Weather Statio
                                            V
                                                                        ....... ......... ... . ..... . ...
                                        ............A
            0.5-


              0-
             00:00   06:00 12:00 18:00 00:00         06:00   1.2:00  18.00    00:00
                 03:00 09:00 15:00 21:00 03:00 09:00 15:00+ 21:00
                                          Time of Day




       Figure 10. Graphs showing air temperature (top), humidity (top) and rainfall (bottom)
                  at Lake Median weather station and BWl airport on July 12 and 13,
                   1990. Arrows indicates beginning of rain event.
                                                    WVV












                Other measurements from the Jabez Branch weather station are

           shown in Figure'10. Air temperatures on July 12 reached a high

           of 31.70C (89.10F) at 15:41 in the afternoon and cooled to around

           290C (84.20F) before it began to rain. At the start of the rain

           event, air temperatures dropped to 230C (73.40F). No monitoring

           devices were established in 1990 to measure the temperature of

           the rain water. it is believed, however, that during the rain

           event the temperature of the rain water will be approximately the

           same as the recorded air temperature. Additional measurements

           will be needed to verify this.



               Figure 11 shows results of temperature and flow monitoring

           along the left fork of Jabez Branch. Station L109, is located at

           the head of the intermittent stream channel and measures the

           temperature of runoff from the upper developed sections of the

           watershed as they flow into the lower forested section. This

           station records air temperature until runoff reaches the probe.

           During the storm of July 12, the recorded temperature at Station

           L109 increased to 25.80C (78.40F) when runoff reached this

           station. The next downstream monitoring station is L003 which

           was located just below the headwaters of the stream in the

           perennial stream channel. At the beginning of the rain event,

           water temperature rises from 17.10C (62.80F) to 190C (66.20F) at

           Station L003. This initial rise was followed by a second rapid

           temperature rise to 23.90C (750F). The last Station is L001,

           which was located near the mouth of the left fork. Temperature




                                      July 12 and 13, 1990
                                            Lower Left Fork
                 30                                                                    86
                 28-.---                                                              -83
                                                                                      -80
                 26
                                        Ll 09!1:,@                                     77
                 24-                                                                       U-
             a)                                                                       -74
                                           ... . .. ........ . .. .....                    a)
                 22----                                                           --71
                                        LO
             CU                                                                            CU
             CD
                 18-                                                                   65  'D
                                                                                           CL
             E                                  LOOII                                  62  E
             a)                                                                            a)
                                                                                      -59
                 14
                                                                                      -56'
                 12                                                                   --53
                 10-                                                        -1   V  ---F50
                 20
                 18
                 16
                 14                              L001:                                7
                 12---
                 10-

            0

                 6-


                      - -- - ------- - ----- . ........ . .. . . ... . ..... . ....... . .........

                 2  . .....              . ............ . .. ..... .. . . . . ..... . ..... . . ... ... . ................
                 0!
                 00.00  06.00 12:00 18:00 00:00          06:00 12:00 18:00 00:00
                    03: 00  09:00    15:00 21:00 03:00       09:00 15:00 21:00
                                             Time of Day




       Figure 11. The top graph shows the temperatures recorded at Stations Ll 09, L003
                    and L001 along the main channel of the left fork of Jabez Branch on
                    July 12 and 13, 1990. The bottom graph shows stream flow (cfs) at
                                           0





































                    Station L001 during the same time period. Arrows indicate beginning
                    of rain event.








           monitoring at Station L001 also indicated an initial rise in

           water temperature from 16.20C (61.20F) to 200C (680F) shortly

           after the beginning of the rain event. The initial small rise in

           water temperature was quickly followed by a second larger

           increase to 23.50C (74.30F).



               Stream flow monitoring indicated that the temperature rise

           at Station L001 corresponded to increases in stream flow. During

           the first rise in water temperature, discharge at Station L001

           increased from 0.3 to 4.0 cfs. This was then quickly followed by

           a second rise to 17.5 cfs as the wave of heated runoff from the

           upper developed portion of the watershed reached this station.



               A similar rise in water temperature was seen in the right

           fork of Jabez Branch at Station R001 (Figure 12). Water

           temperature in the lower right fork rose to a high of 23.20C

           (73.80F). The change in water temperature, however, was not as

           great as that on the left fork because base flow water

           temperature on the right fork was already higher.



               In addition to changes in temperature, both the right and

           left forks of Jabez Branch experienced similar changes in stream

           pH following the rain event. At the beginning of the storm the

           pH of both the left and right forks dropped 0.4 and 0.9 pH units

           respectively. This initial drop was soon followed by a rise in

           the pH of both streams to around 6. An earlier profile survey of

           the left fork of Jabez Branch indicated that the middle portion





                                                  July 12 and 13,1990
                                                        Left vs.Right Forks
                     30-                                                                                          86
                     28-                                                                                         -83
                     26-                                                                                         -80
                                                                                                                 -77
                     24-                                                                                                U-
                                                                                                                 -74
                     22-
                                           Right_,,j@J1                 J-1
                     20-
                                                                                                                  68    cu
               CD
                                                                                                        --65            (D
               CL    18-                                                                                                CL
               E     16-                                                                                         - 62   E
              IT                          Left                                                                   -59
                     14-
                                                                                                                 -56
                     121                                                                                            3
                     101
                                                                                                                  50
                       8-                                                                                         8
                    7.5 - - - - - - - - --------- - - -----                                 . .............................................. ......... -7.5 01

                                                                                          . . ......... . ................................ . .. . ......... -7

                    6.5 . ........ .. . . .. ........... ... ........ ............ .... . ..... ....... .. ......
                                                                                            ... ............................  ..............
                                                                                                                  6.5
                                           Right_
                                                                         . ................ .... .... ............................ ...........................
             CL                                                                                                  -6
                                                                                                                         CL

                                                                                                          ------------
                              ---- ------- - - - -- . ...........................
                                                                                                     .....................................
                                                                                                                  5.5
                                             Left
                      5 . ........                                       . . . . ........................... . . . .. . . . ...... . ....................  .................................... -5

                             . ........ . ...... . ........ . ..... . .. ............ .. . ................. . ...... .I............................. . .... ............. . ... . . .......... . ....................................... -4.5
                      4                                                                                          -4
                     00:00 06:00          12:00      18:00 00:00 06:00 12:00 18:00 00:00
                         03:00 09:00 15:00 21:00 03:00 09:00 15:00 21:00
                                                           Time of Day




          Figure 12. Graphs showing comparisons of continuous temperature (top) and pH
                         (bottom) measurements from the left and right forks of Jabez Branch
                         on July 12 and 13, 1990. Arrows indicate beginning of rain event.








           of the stream did have reduced pH levels (Figure 5). The initial

           drop in pH seen at Stations L001 and R001 may be due to either

           the reduced pH water upstream moving downstream quickly at the

           beginning of the rain event or because the pH of the runoff

           entering the stream at the beginning of the storm is lower.

           Additional monitoring of pH above Station L001 will be needed to

           determine the cause of the changes seen in 1990.



               Temperature monitoring results in the upper intermittent

           channels of the left fork of Jabez Branch are shown in Figure 13.

           The arrow on the graphs indicates the start of the July 12 rain

           event. Prior to the beginning of the rain event, the temperature

           recorders are measuring air temperatures in the intermittent

           stream channels. Temperature recorders at Stations L101, L102

           and L103 monitored the runoff primarily from agriculture land.

           Results indicated that at the beginning of the rain event, the

           temperature of the runoff at these stations, as initially around

           230C (73.40F). As the storm progressed temperature measurements

           at these stations rose to 250C (770F). Stations L106 and L107,

           on the other hand, receive runoff from the more urbanized

           sections of the watershed (Table 3). The temperature monitors at

           these stations showed that the runoff from the more urbanized

           sections was initially above 270C (80.60F) and then dropped to

           just below 250C (770F). In contrast to these stations in the

           upper watershed, Station L110 measured the temperature of runoff

           from a 96 % forested drainage basin. The temperature of the

           runoff from the forested section of the left fork remained fairly





                                                         July 12,1-990
                                                          Upper Left Fork
                     30-                                                                                            86
                     29-
                     28-                                             . .....               . ... . .......... . ... . . .................................... . ....... -82
                     27-                                                       . . . ..................... ................. . . ........................................ ....... U-
               a)             Ll 02                                                                                -80
                     26-ziz                                                              . .... .. . . ............. . . ......... .............
                                                                                                                   -78
               75    25-
                               Ll 01                                                                     wji"      -76
                                   ..........                                                    .. . ..... .... . .................................-
               CL                                                                                                          CL
               E
                                                                                                                   -74     E
                     23-
                                                                                                       . . .. . . . .........  --.-72
                     22-:
                                Ll 03


                     20+                                                                                            68
                     30-                                                                                            86
                     29 . .....    - - - ---------------------                 . . . . ................. . . . ... . . ..................................................... ........ ---84

                                                        . ........ ..... . .............. . . ............................... . ................. ................. ............................................. .. ... . .......... -82
                                      Li 06 Vq,                                                                            U-
                     27------                                    07  ..... . ... - --- - - - - --- - --------------------- ----- - -----------------------------------------------------------
               a)                                                                                                  -80
                                                                                                 ......... ..........  ............
                     26 - - - ------- - - - -- ----------------------------x. . ..... ...... . ............ ...... . ... . .............. ...*................ . ...... =3
                                                                                                                   -78     -6--j
                                            ...... ..... ... . ............. ........ ..... . . ...... ..... . . . . . . ........................ . ................... . ....................... Cz
                              . ......... .
                                                                                                          Ali-  ..............
                                                                                                                   -76
                                            ..... .......... ..... ... ..... ... . ........... . .. ...... ........
                                     . ... .. ........                                                                     CL
               E                                                                                                   -74     E
                                                             ....... . ................................................ . ... . ........ ...... .. ... . ...... . ............... ...............................
               a)    23-                           . .. .......
                           LI 09                                                                                           F-
                                                                                                                    72
                     22 . .............. . ................. ...........  ...........................................
                                                                         L110                                      -70
                           ............ . ............ . .....................
                     21-----                X                      . ................... . . . ........ .. . . .... ............... ..... . ... . ........................................... . .......................
                           ...X--><--X'X--XX--X
                     20--                                                                                           68
                     18:00 18:20 18:40 19:00 19:20 19:40 20:00 20:20 20:40 21:00
                           18:10 18:30 18:50 19:10 19:30 19:50 20:10 20:30 20:50
                                                             Time of Day



           Figure 13. Temperature measurements from intermittent drainage channels in the
                           upper left fork of Jabez Branch on July 12, 1990 between 18:00 and
                           21:00. Arrows indicate beginning of rain event.









           constant at around 220C (71.60F).



              Results of monitoring at the two special land use stations

           are shown in Figure 14. On July 12, the temperature of the

           road's surface (Station RoadTe) reached a high of 45.30C

           (113.50F)'and cooled to 370C (98.60F) just prior to the beginning

           of the rain event. The road's surface temperature then dropped

           to around 300C (860F) shortly after it began to rain. The probe

           measuring the temperature of the highway runoff was positioned

           just above the road's surface and tended to remain approximately

           60C (10.80F) below the temperature of the road surface in dry

           weather. once the rain started, the temperature of the water

           running off of the highway was initially just below 280C (82.40F)

           and later dropped to between 260C (78.80F) and 250C (770F).



               Results of temperature monitoring of runoff from an

           industrial roo f in the watershed indicated that the temperature

           of the roof runoff at the beginning of the storm was 24.50C

           (77.90F). As the storm progressed, the runoff temperature

           dropped to between 230C (73.40F) and 220C (71.60F).





           August 5 & 6, 1990 0.37 inches of rain)



               August 5 was a,cloudy humid day with air temperatures

           reaching a high of 27.20C (810F) at 15:52 (Figure 15). Trace





                                           Ju  ly 12,1990

                40-                                                                    105
                38--  MIR
                                                                                       -100
                36-
                34--                                                                         U_
                32-                    oadTe-.

                                                                                             Cz
           cu   30                                                                     -85
           a)
           cL   28-
                                                              ...........
           E                                                                           80
                                                                                             E
                26-                  HOO1                   zt.=-
                24-                                                                    75
                                                                                       -70
                20.1                                                                   65
                40                                                                     105

                                . ...........
                   .......................... ... . .... ..... . . . . .................. . .. ........ . .......... . ..................... . ......... . ...... . .... . ........ . .... . ............. .............. . .................................... -100
                36-11 ............* *'*'**'* - - ---- 11_1"11--*"1_1**_1-, ....... . ..I---------------- ------------ . .......................................... . .. ............................................. .......... . ............I........... . .................................
                   . .. . . ............... . .... ..................................... ........... .... . ................ .................... . ........ . .. . ....... . .. . ....... . .. . ..........................
                                                                         . . . ....................  ................... .@ 95
           '(21                                           . . . . . . . ... ............. . .. . .... . . . .. . . . . ................ .......... . .. U_
           CD
                32-                                                               . ........ -90 CD

                                                         . . . . . ..... ... . .............. . . . .. ......

                                                . . . ............        . . .................... . . ......
                                                                                       r85   Cz
                   .... ......... . ......... .. . ........................ ............... . . ..... . . ........... ...... .......... ...... . . .............................. . .......................... ....... ....... ................... . . . . ...... . .............. ...
           a.   28-J .. . . .. ..... . ................. . .................... - - - -- - --- - ---- - --------- - -------------------- ------------- - ----_-------- ------- ----- . .. . . .................. .. ..... . ....................... ..
                   I-- _-...- . ........... .                 . ..... . .......... ... .......... L! 0_
           E                                                               . ........ . . .........E
                26 @... ..... ..... Roofol -- - - - - -- - ----- - - --------------------- . .... . .......... .. . . . ..................... .
                   7-  ....                               . . . . ............ . .................................. -75
                24 . . . . . .. .. ... ................................. .... . ...

                                           . . ...... ... ... .... ..... .....  ..... ...  .......... . .....
                22                       . . . . . ............ . . ..... . ... . . ....... . .. . .......... ...... -70

                                                                             . . . . . . ................
                20!001181                                                        1 ! 65
                18.       :20 18:40 19:00 19:20 19:40 26:00 20:'20'20:'40 21:00
                   18:10 18:30 18:50 19:10 19:30 19:50 20:10 20:30 20:50
                                             Time of Day


      Figure 14.   Temperature measurements from the special land use monitoring stations
                   in the upper watershed of the left fork of Jabez Branch on July 12,
                   1990 between 18:00 and 21:00. in the top graph Station RoadTe
                   shows the temperature of the surface of Rt. 3 while Station H001
                   shows the temperature of the highway runoff. The bottom graph
                   shows the temperatures measured in the drain from an industrial roof
                                Au&AAAr
                                . . ..........,
                                          Alk


                                             . . . .... ...... .....

















                   in the watershed. Arrows indicate beginning of rain event.






                                          August 5 & 6,1990

                   3                                                                    100
                                                    ..j Humidity@                       95

                                                                                       -90
                   30---
                                                                                        85

                                                                                       -80     >1
                                                               . . ......... .. . . . .. .........
              W    25
                                                                                        75
              CL                                                                               E
              E                                                                        -70
              a)   20-                                       perature@
                                                    Air Tem

                                                                                       -60
                   1-5-                                                                -55
                   .3-




                                     BWI Airpo                   A Total Rain Gauge
              Ca





                   0-
                   00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00
                      03:00 09:00 15:00 21:00 03:00 09:00 15:00 21:00
                                               Time of Day



      Figure 15. Graphs showing air temperature (top), humidity (top) and rainfall (bottom)
                   at Lake Median weather station and BWI airport on August 5 and 6.
                   Arrows indicate beginning of rain event.
                                                 rt









           amounts of rain were reported throughout the day at BWI Airport

           with a moderately size rain event occurring in the evening

           (Figure 15). Data from the field weather station and the backup

           rain gauge at Jabez Branch indicate that the rain event occurred

           at night at approximately 23:00. The exact time it started to

           rain in-the Jabez Branch watershed is unknown because the tipping

           bucket rain gauge at the field weather station was not

           functioning. The backup rain gauge which measures total rainfall

           indicates that 1.37 inches of rain fell in the area that night.



                Figure 16 shows the temperatures recorded at Stations L001,

           L003 and L109, along the left fork of Jabez Branch, and stream

           discharge at the USGS gauging station. Temperature measurements

           show the same general patterns as those of the July 12 rain

           event. At the beginning of the storm a small immediate rise in

           water temperature occurred at Stations L003 and LOOI along with a

           rise in discharge at Station L001. This initial rise was then

           followed by much greater temperature and flow increases. The

           increase in temperature and flow, however, were not as great as

           had been seen on July 12. Water temperatures on August 5

           increased only 5.20C (9.40F), as opposed to the 7.30C (13.10F)

           that occurred on July 12. The difference in the size of the

           temperature increases between the two rain events is believed due

           to three reasons. -First, the amount of rainfall on August 5 was

           only half as much as on July 12. Second, air temperature on

           August 5 reached a high of only 27.20C (810F) while on July 12

           the high for the day was 31.70C (89.10F). Finally, the rain





                                        August 5 & 6,1990
                                             Lower Left Fork
                 30-                                                                     86
                 28-


                                                                   . .........
                 26-
                                                                                        -77
                 24-                        -LOOf--                                     -74
                 22--                                                                    71
            CO   20-@:`s--                     LOO                                      -68   75
                                                                                         65
            CL   18-                                                                          CL
            E                                                                           -62   E
                 16-                                                                          d)
                                                      Ll 09                             -59
                 14-                                                                   --56
                 12-                                                                -.-53
                 10-                                                                     50
                 20-

                 1.8-

                 16--

                 14--


            U
                 10-                                                      . ...... ...............
            0    8-                                                             . . . ......
            U-
                 6]
                 4
                                                         L001
                 2                                 . ...... .. ... . ............

                 0-
                 00:00 06:00 12:00 :18:00 00:00 06:00 12:00 18:00 00:00
                    03:00 09:00 15:00 21:00 03:00 09:00 15:00 21:00
                                               Time of Day
       Figure 16.   The top graph shows the temperatures recorded at Stations 1-109, L003
                    and L001 along the main channel of the left fork of Jabez Branch on
                    August 5 and 6, 1990. The bottom graph shows stream flows (cfs) at
 0                  Station L001 during the same time period. Arrows indicate beginning
                    of rain event.









           event on August 5, occurred at night (23:00), whereas on July 12,

           the rain started in the late afternoon (18:30). Because the rain

           event occurred at night on August 5, roads and other surfaces in

           the watershed had some time to cool. However, despite the fact

           that the August 5 rain event occurred at night following only a

           moderately warm day, water temperatures in the left fork of Jabez

           Branch still exceeded the Maryland water quality standard for

           natural trout waters of 200C (680F).



               Monitoring data for pH was obtained only from Station L001
           during this time period. The pH levels (Figure 17) at Station           0'
           LOOI showed the same initial drop at the beginning of the rain

           event as on July 12 (Figure 12) before rising to around 6.



                Results of temperature monitoring of runoff in the upper

           drainage channels on the left fork are shown in Figure 18. Prior

           to the beginning of the rain event, these recorders measured air

           temperature. At the start of the rain event, the temperatures of

           the runoff at Stations L101, L102 and L103 were all around 220C

           (71.60F). Temperatures then rose slightly at Stations L101 and

           L102 to 230C (73.40F), while at Station L003, the temperature of

           the runoff dropped to near 210C (69.80F). At Stations L106 and

           L107 which drain more developed sections of the watershed, the

           temperature of the runoff was just below 240C (75.20F). At

           Station L110, which monitors the runoff from a forested section

           of the watershed, the temperature of the runoff was just below

           22-C (71.6-F).




                                          August 5 & 69 1990
                                           Station L001 Hydrolab
            30-                                                                                         8
            28  . ............................................................................................................................................................................................................... .... . ....... . .. . .. ..... . ..................  ........... -7a5
            26  . ............................................................................................................................................... . ............................................................. ..........................................................  ............
                                                                                       ...................................................... -7
      C)    24  . ..................................................................................................................................................................................................................................
       a)                                                                                              -6.5
            22  . ......................................................................................................................................................................................................................................................................................
            20  . ...................................................................................................................................  ..... ... ..............................................................................................
                                                                                                 ................... -6
                                      Temperature
            18  . .................................................................................................I...................................
                                                              .......................... ........ ........ ............................................................
                                                                                                        5.5
                           ---------------           ......
       E
                                                              ............................ ........... ......... ...... ........
            16  . ............................................................. ..............................................................
                                                                pH                                     -5
            14  . .......................................................................................................................................................I..............................................I...............................................................................
            12  . ........................... .......................  .................................................................................................................................................................................................................................. -465
            10        1     1         1     1    1    1 It I     I    I     I    I    I     I    1     14
             00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00
                  03:00 09:00 15:00 21:00 03:00 09:00 15:00 21:00
                                                   Time of Day


                   Figure 17. Graphs showing continuous temperature and pH measurements from the
                              left fork of Jabez Branch on August 5 and 6, 1990. Arrow. indicate
                              beginning of rain event.






                                                                     August 5 & 611990
                                                                             Upper Left Fork
                             30                                                                                                                        86
                             28--                                                                                                                      83
                                                                                                                                                       -80
                             26--
                                    -                             Ll 02                                                                                77
                       C)                                                                                                                                       U-
                                                                                                                 .. ....     . ........ ..... ....................  --..-74
                       CD                                                                                                                                       a)

                                                                                                                           -----------
                                                                                                                                                                =3
                                                                                                                                                       -71      1-
                                                                                                                                                                Cu
                       1@    20                                                                                           L103-                        68
                       CD                      Ll 01                                                                                                            CD
                       CL    18-                                                                                                              ---65             CL
                       E                                                                                                                               -62      E
                       a)    16-                                                                                                                                a)
                             14                                                                                                                    -.-59
                                                                                                                                                       -56
                             12
                             10-
                                                                                                                                        1 1            150
                             30                                                                                                                        86
                             28                                                                                                                        83
                             26-                                                                      . . . . .... . ...... ......................... . .. ...................... . ... . .... . -T80
                                                                         Li 09                                                                         -77
                       C)                                                                                           . . . ........ - ---------- . . ........... U-
                             24                                                                                   .......                              -74
                                                                                                                                                                (D
                             22-                                                                              . . . ......       . ..... . .................. ....... ...
                                                                                                 - -----------------                                   -71
                                                --- ------------  ---------------         ---- --                      ---------------------------              =3
                                         .... . ............... ....... ... .. .. .. .... ... .. ............ ............
                       Cu    20-                                                                                       Ll 10     . ..... . ...................... 68 cz
                       a)                                  Ll 07
                       C-                                                                  L 106                                                       65
                       E                                                                                                                               62       E
                       0     16-                                                                                                                                CD
                       F-    14-                                                 . . . . . . . .............. . .... ....... . . . . .... . .................... .5 9
                                                                                                                                                       56
                             12                                        . . . . ... .......... . ......... ....... . ............ .         ................. .... -63
                             10
                             18:00 19:00 20:00 21.00 22:00 23:00 00:00 01:00.02:00 03:00
                                   18:30 19:30 20:30 21:30 22:30 23:30 00:30 01:30 02:30
                                                                               Time of Day


           Figure 18. Temperature measurements from intermittent drainage channels in the
                                upper left fork of Jabez Branch on August 5 and 6, 1990 between
                                18:00 and 3:00. Arrows indicate beginning of rain event.








0               Results fr om the two special land use monitoring sites are
           given in Figure,19. The temperature of the road's surface

           reached a high of 37.20C (98-60C) at 12:45 and cooled to 260C
0          (78.80F) at the beginning of the rain event. Due to equipment
           problems,'no measurements of the temperature of the runoff for

           the highway were obtained. The temperature of the water from an
0          industrial roof was 230C (73.40C) at first and dropped to 220C
           (71.60C) later in the storm.




0
           September 16 & 17, 1990 0.14 inches of rain)



               The final rain event occurred on September 1 6 and produced

           1.14 inches of rain. Air temperatures preceding this rain event

           reached a high of only 23.40C (740F) at 14:55. Air temperatures

           then dropped to 20.90C (69.7*F) before it began raining at 17:30

           (Figure 20).



               As shown in Figure 21, monitoring stations along the main

           stream channel of the left fork of Jabez Branch recorded much

           smaller temperature rises for the September 16 rain event than in

           the other two previously discussed storms. Results from Station

           L109 indicate that the temperature of the runoff from the

           developed upper section of the watershed reached a high of only

           19.50C (67.10F). As runoff moved downstream to Station L003, the





                                       August 5 & 6,1990
                                            Upper Left Fork
               40-                                                                     105
               38-                                                                     100
               36-                                                                     95
               34--                                                                           U-


           CO  30-                                                                     85     M
                                                       Roaffe@
           CL  28-                                                                     -80
           E                                                                                  E
           CD  26-                                                                            CD
               24-                                                                     -75
               22                                                                      -70

                                                                                       65
               20-
               40-                                                                     105
               38--                                                                    -100
               36-                                                                 . . ....

                                                                                              U-
               34-
                                                                                       -90    CD
           Q2  32---
           =3
           Cz
           (D                                                   . . . . . . . . ... . . . ............ . ................ .0-
           0-  28-                                                                     80     E
           E
           W   26---
                                                                                       -75
               24 .......                      - - - - - ------------ - ----- --------- RoofOl
                                                                                       -70

               20 -                                                                    '65
               18:00 19:00 20:00 21:00 22:00 23:00 00:00 01:00 02:00 03:00
                   18:30 19:30 20:30 21:30 22:30 23:30 00:30 01:30 02:30
                                             Time of Day -

       Figure 19.   Temperature measurements from the special land use monitoring stations
                    in the upper watershed of the left fork of Jabez Branch on August 5
                    and 6, 1990 between 18:00 and 3:00. in the top graph Station
                    RoadTe shows the temperature of the surface of Rt. 3, and the bottom
                    graph shows the temperatures measured in the drain from an industrial
                    roof in the watershed. Arrows indicate beginning of rain event.






 0

                                          September 16 & 17,1990

                25-                                                                                                 100
                                                                     Humidity
                            AI                                                                                     -95


                                 ..... ...... ... . ...... ......... ............ ............................ . .... . . ....
                20-                                                                   ............... --- ---------- ............... ............... 7. -90
                                                                                J;
                                                                                                                     85      -0-0,
                                                                                                                   -80
                   -4  . .....        ... . ........ .... . ......
                                                                                     ... ........ . . .....
                                                        V, -V .... . ......
                15
          E
                                                                                                                   -75

                                                                                                                   -70

                                                                                     .. ... .. ....           ................
                10
                                                                                                                   -65
                                                                  emper         re
                                                                                                                   -60
                                                           ArT

                  5                                                                                                  55
                 3-





                 2-
                                                              . .............. .............. . ........


                                                      Total Rain     Gauge
                                            . ..............
        Cz    1.5@
                                                                          ............

        C
        Ca
                     .-- +
        CE         . .....                                          . ... . ......
                               Weather StatJon.              I
                               ..........        -------




                 01
               00:00      06:00        12:00       18:00      00:00       06.
                                                                              .00     12:00       18:00       00:00
                     03:00 09:00 15:00 21:00 03:00 09:00 15:00 21:00
                                                         Time of Day


        Figure 20. Graphs showing air temperature (top), humidity (top) and rainfall (bottom)
                          at Lake Median weather station and BWl airport on September 16 and
                          17, 1990. Arrows indicate beginning of rain event.
                                                                                                           Kl@





                                         September 16 & 17,1990
                                                   Lower Left Fork

                  30-                                                                                            86
                  28-                                                                                            83
                  26-                                                                      ..... . ............................... -80
                                                                                                               -77
                                                                                             ........ . . .......... ........ . ............. . U-
                  24-                                                                                          -74
                  22-                                                                                 . ....... . ... . ....
                                      Li 09      . .. ..... .                        . . . . .... . .. . ..... . . . . .............. . . . ....... . . . ... 68
                  20-
                      -                                                                                        - 65     (D
            CL    18                                                                                                   CL
            E                                                       L003                                       -62      E
            0     16-                                                                   .... . . .... ........ ...... . (D
           F-                                                                                                  -59
                  14-                                    1-001-                       . .............. . .......-- %op V
                  12--                                               .. . . . . .. ........                    -53
                                                                                                                 5 0
                  10 i                                                -7     -1

                  20-
                  18-


                                                                                         ..... . ........



                          - - - --- - -- - - - - - - -------- - -------------------- ........ . ......... .......... ........... -- - --- ------ ------ ----- . ......


                                                                                                      ............ . ..... . ......
                                          . ... ....... ........................................ .... ......... . ... . ............. . . ...........


                  10-               ...... . ...........I..... ...........I............... . ........... . .. - ------ .... ......... .... . .......... ... ....... . . ..
             0                                         --- - --------- - ----- - --------- *--"--,,---,-**,*--"-*-*---"",----"--* ............
            EE
                                - - ---------------------------------- -------- ---- - - - -- -------------- - -------------- ...... ....... .--- - - -------,.........................
                                                      L001                                                ..........
                                             - - - ---------------        . ...... . ...........*............ . ....... ..*. ..... ..........

                                                                                     ............ ..................
                    2 . ........             ............ ... ..
                    0-              -7-
                  00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:00
                       03:00 09:00 15:00 21:00 03:00 09:00 15:00 21 '00
                                                         Time of Day
          Figure 21.      The top graph shows the temperatures recorded at Stations Ll 09, L003
                          and L001 along the main channel of the left fork of Jabez Branch on
                          September 16 and 17, 1990. The bottom graph shows stream flows
                          (cfs) at Station L001 during the same time period. Arrows indicate
                          beginning of rain event.









           water temperature high dropped to 17.70C (63.90F). Finally, when

           the runoff from the upper portion of the watershed reached

           Station L001 at:*the mouth of the left fork, only a 0.60C (1.10F)

           rise in water temperature to 16.10C (610F) was recorded. The

           peak flow at Station L001 was 3.8 cfs (Figure 21).



                As reported in the two previously discussed rain events,

           both temperature and pH changes followed the same patterns on

           both the left and right forks of Jabez Branch (Figure 22). Water

           temperatures on both streams rose around 0.50C (0.90F) and pH on

           both forks initially dropped at the beginning of the rain event

           and then rose to around 6 when runoff from the upper portion of

           the watershed reached the mouth of both forks.




                In the upper developed portion of the watershed, the

           temperature of runoff from urbanized sections of the watershed

           (Stations L106 and L107) was above 190C (66.20F) (Figure 23).

           Runoff temperature from the more agricultural areas (Stations

           L101 and L102) were between 170C (62.60F) and 190C (66.20F)

           (Figure 23).



               Figure 24, shows results from the two special land use

           sites. At the Rt. 3 site, the temperature of the surface of the

           highway reached a high of 46-20C (115-20F) at 15:05 in the

           afternoon and cooled to around 280C (82.40F) before it started

           raining. After the rain began, the temperature of the runoff

           from the highway was 220C (71.6*F). The temperature of the






                                           September 16 & 17,1990
                                                  Left vs. Right Forks
                   30-                                                                                             86
                          - - - -------- - ---------                                              . ..... .. . .. ............  _-..__....-83
                                                                                                                 -80
                   26-                                                      . . . . . ... . ............. ........... ..... . ..I...... . ........ . .....................
                                                                                                                 -77
                                                                                                         .......................... U_
                                                                                                                 -74
             0
                                                                                                        ......................
                                                                                                                 -71
             CO    20---                                                                          . . .... . ............... . . . . .
                                                                                                                   68    cz
                                                       ---Right                                                          cD
             C)_   18-                                                                                                   CL
             E                                   . ...... . .                                                            E
                   16 -
                                                                                                                   59
                                                                                                         .............
                                                                       Left                                     ""-56
                   12                                                                                            - 53
                   10-                                                                                           150
                  8.0-

                  7.5-

                  7. 0 -      . ...... . ......... ......... .......... . ........ ........ . .............. ......


                          . ..... ........... . ......... - - ----- . ...... - ---- - ------ - ----
                                                     Left

                                                                             .......................................... ... . ..............
                                                        . . ... ........
                  6.0 . ........               . ...... .......... .......
              CL                                    ... ....1


                                  . . . ............ ..... . .... . . ....... . . . .. .............. ..... . . .... . ....... . ...... - ---------- -
                  5.5 . . ........... . .......


                                                     . . .........
                  5.0 - -------------------- ------ -........ . .............. . ... .. ...........W
                                                           Right "*'*'*-"***""-'*'-'-'* - - - - --- ------- ------ . .....*. .............

                              .............. . . .. .............. .......... .. ............... ..................................................... . ......................................... . ................................ . .................... .................. . ...... . .. ......... . .......
                  4.5 . ................. .. .

                  4.0
                   00:00 06:00 12:00 18:00 00:00                            06.00 12:00 18:00 00:00
                         03:00 09:00 15:00 21:00 03:00 09:00 15:00 21:00
                                                            Time of Day


         Figure 22.     Graphs showing comparisons of continuous temperature (top) and PH
                         (bottom) measurements from the left and right forks of Jabez Branch
                         on September 16 and 17, 1990. Arrows indicate beginning of rain
                         event.
                                                                 . . ... . . ...






0


                                        September 16,1990
0                                           Upper Left Fork
                 30-                                                                        86
                 28-                                                                 .----83
                 26-                                                                      -.-80
                                                                                           -77
                 24-                                                                             U-
                                                                                           -74
                 22--L102-                                                                --71
                                                                  Ll 01..
             CO                                                                            --68  CU
             CL                                    X-:                                      65
                                                                                                 CL
             E                                                                             -62   E
                 16-
                 14-                                                                       -59
                                                                                           -56
0                12-                                                                       -53
                 10-                                                                       -50
                 30-                                                                       -86
                 28-                     . . . . . ...........
                 26-
                                                                                           -77
                 24--                                                                            U-
                                        Ll 06                                               74
             Q)
                 22 . ......           ..... - - ---- ---- - ----- - --
                                            L1 07                                          -71   15
             Cu
                                     -X ................... . ........
                                                       A
             C-  18-                                                                        65
             E                          -109                   . .................. . . . ............E
             CD  16-                                                                             CD
             F-  14-                                     Ll 10                             -59   1--
                                                                                           -56
                 12.----                                                          ----'-53
                 101                                                                       -50
                 17:00 17:20 17:40 18:00 18:20 18:40 19:00 19:20 19:40 20:00
                     17:10 17:30 17:50 18:10 18:30 1,8:50 19:10 19:30 19:50
                                                Time of Day


      Figure 23. Temperature measurements from intermittent drainage channels in the
                  upper left fork of Jabez Branch on September 16, 1990 between
                   17:00 and 20:00. Arrows indicate beginning of rain event.





                                            September 16,1990
                   30                                                                             86
                                                                                                 -83
                   28
                   26-                                                                          --80
                                                                                                  77
                   24--                                                                                U-
                                                                                                 -74
                                                     RoadTel
                                          X--X                                                   -71   M
                                        x                                                              4."
               Ca  20-                                                     . ..... .. .. ........  -68 CU
               CD                                          HOOt
               C)- 18--                                                                           65
               E                                                                                       E
                                                                                                       CD
               a)  16-                                                                                 1--
                                                                                                 -59
                   14                                                                            -56
                   1'21-                                                                          5
                   10 i
                   30                                                                             86

                   28
                                                                                                 -80
                   26                                                                            -77
                   24-                                                                                 U-
                                                                                                  74   1.-,
                                                                                                       CD
               21  22-                                                                           -71   L-
               =3                                                                                      :3
               CU  2u-                                                                           -68   cu
                       -A@
                                                                                                       a)
               CL  18-                                                                       ---65     6-
               E                                      RoofOl
                                                                                                 -62   E
                                             . .........
                   16-                                 LL
                                                                                                 -59
                   14
                                                                                                 -56
                   12

                   10-                                     1   1   T--                            50
                   17:00 17:20 17:40 18:00 18:20 18:40 19:00 19.
                                                                                .20 19:40 20:00
                       17:10 17:30 17:50 18:10 18:30 18:50 19:10 19:30 19:50
                                                    Time of Day

         Figure 24.    Temperature measurements from the special land use monitoring stations
                       in the upper watershed of the left fork of Jabez Branch on September
                       16, 1990 between 17:00 and 20:00. In the top graph Station RoadTe
                       shows  the temperature of the surface of Rt. 3 while Station H001
                       shows  the temperature of the highway runoff. The bottom graph
                       shows the temperatures measured in the drain from an industrial roof
                       in the watershed. Arrows indicate beginning of rain event.










           runoff from the industrial roof during the September 16 storm was

           initially 17.1 C (62.8F) and later dropped to 15 C (59 F).



















































 

                             Discussion



       The principal objective of the first summer of non-point

thermal pollution monitoring on Jabez Branch was to collect

baseline data on land uses, runoff patterns and runoff

temperatures from different sections of the Left fork watershed.

This information is needed for furtre analysis that will combine

recoreded runoff temperatures with estimate of the volume of

runoff orginiating from different sections of the watershed.  By

combining temperature measurements with estimates of runoff

volumes, the thermal loadings from each area can be determined.

The ultimate goal of this work is to develop a thermal loading

budget for the left fork of Jabez Branch which can be used to

determine the relative effects of different land uses areas on

temperature changes in the stream.



     Results from the 1990 land use surveys indicate that nearly

50% of the left fork watershed of Jabez Branch remains forested

and much of the remaining land is in agricultural use.  It is

estimated that a present less than 4% of the left fork

watershed is covered with impervious surfaces. Despite the

fairly low level of urban development, results indicate that

temperature near the upper tolerance limit of Brook trout.  The








           relatively large rises in stream water temperatures appear to be

           the result of two factors. First, the left fork of Jabez Branch

           is a small stream with a summer base flow of only 0.3 cfs.

           Because normal base flow in the stream is low, even a small

           amount of warm surface runoff can have a dramatic impact on

           stream water temperature. The second factor is that development

           in the left fork watershed is concentrated in the upper sections

           of the drainage basin. When it rains, it appears that runoff

           from commercial, residential and agriculture land in the upper

           watershed concentrates in drainage channels and quickly flows

           down stream. This runoff has not only been heated from contact

           with roads and other warm surfaces, but the volume of water

           originating from the upper watershed is also believed to be

           fairly large. As this heated runoff moves down stream, it

           changes water temperature along the entire length of the left

           fork of Jabez Branch.




                Results indicate that the magnitude of the water temperature

           changes resulting from non-point source thermal pollution in

           Jabez Branch depends on the intensity of the rain event and

           meteorological conditions prior to the storm. Small rain events

           producing less that 0.25 inches of rain had no effect on water
           temperature in Jabez Branch. Almost ail of the rain water during

           these small events is retained on the land and little or no

           overland runoff to the stream is generated. For storms that

           produced more than 0.25 inches of rain, the magnitude of the

           water temperature rise in the stream depended on the time of









           storm occurrence, the intensity of the storm, the amount of

           runoff generated and how warm the day was prior to the start of

           the storm event".* The largest rise in water temperature observed

           during 1990 occurred on July 12 during a 2.65 inch rain event

           that occurred in the late afternoon (18:30) on a fairly warm day

           (31.71*C-or 89.10F). Water temperature on the left fork rose from

           170 (62.60F) to 23.90C (750F). Other storm events produced small

           temperature rises in the stream, however, it is important to note

           that during the summer of 1990, all storms that produced an inch

           or more of rain occurred in either the late afternoon or at night

           after surface cooling had started. No significant rain events

           occurred during mid-afternoon when roads and other surfaces in

           the watershed tend to be the hottest. It is believed that a

           large afternoon thunderstorm on a very hot day would generate the

           warmest runoff and largest temperature rise in the stream.



               The data collected during 1990 provides important

           information on the differences in runoff temperatures from

           different subdrainage basins in the Jabez Branch watershed. On

           July 12, meteorological data collected at the Jabez Branch

           weather station indicated that air temperatures dropped from 290C

           (84.20) to 230C (73.40F) at the beginning of the storm.

           Although the temperature probe at the Jabez Branch weather

           station is sheltered and designed to measure air temperatures, it

           is believed that air temperature during a rain storm is also an

           indication of the temperature of the rain water. Additional

           measurements, however, will need to be done in 1991 to verify









           this. Runoff monitoring indicated that the temperature of the

           runoff from forested land (Subdrainage Basin X, Figure 3) was

           around 22.50C (72.50F). This is very close to air temperatures

           during the storm and suggests that the temperature of runoff from

           a forest will be close to the temperature of the rain. In the

           more developed sections of the watershed the temperature of the

           runoff was warmer. The warmest runoff came from Subdrainage

           Basin VI which was also the most urbanized subdrainage basin.

           Initially the runoff from Subdrainage Basin VI was just below

           28-C (82.4-F). This is the same temperature measured at Station

           H001 which monitored the temperature of the runoff from Rt. 3.

           As the storm progressed, the temperature of the runoff from

           Subdrainage Basin VI and the other more urbanized subdrainage

           basins dropped to around 24.50C (76.10F). In the  more

           agricultural areas of the watershed, the temperature of the

           runoff was initially around 230C (73.40F) which was only slightly

           above the temperature of the runoff coming from forested lands

           (Subdrainage Basin X). As the storm progressed, however, the

           runoff from the mostly agriculture areas increased to around 250C

           (77-F).



                In addition to the increased temperatures, it is important

           to remember that the volumes of water coming from these areas

           also increased. in a forest, only a small amount of water

           reaches the stream as overland runoff while almost all of the

           rain water that falls on a road or parking lot will quickly move

           into the stream as overland flow. It is believed that the






0


           combination of increased water temperatures and increased water

           volumes from urbanized sections of the watershed are responsible

           for the temperature rises seen in Jabez Branch.



                During this study, the largest rise in water temperature in

           Jabez Branch occurred during a large storm on July 12. Smaller

           rain events, however, did produce significant stream water

           temperature rises, even when they occurred at night. On August 5

           for example, the rain event occurred at night (23:00) following a

           cloudy day when air temperatures had reached a high of only

           27.20C (810F). Despite these fairly moderate weather conditions,

           water temperatures in Jabez Branch still rose 50C (90F) from 160C

           (60.80F) to 21-C (69.80F). During the rain event on August 5 air

           temperatures were 220C (71.60F) and the temperature of the runoff

           from all of the monitored subdrainage basins except the forested

           Subdrainage Basin X was around 230C (73.40F). The runoff for

           Subdrainage Ba sin X was slightly cooler at 210C (69.80F). This

           means that even with very little heating of the runoff from

           contact with roads and other surfaces in the upper watershed, the

           temperature of the water in the stream still rose above the

           Maryland water quality standard of 200C (680F). These results

           suggest that since the temperature of rain can frequently exceed

           200C (680F) any change in land use that increases the amount of

           surface runoff entering a trout stream will increase water

           temperature fluctuations. Trout, however, are capable of

           withstanding small temperature rises above 200C (680F) so long as

           the increases are not for an extended duration.











                one surprising finding in 1990 was the relatively low pH in

           the center portion of the left fork of Jabez Branch. During base

           flow conditions the pH in the mid-section of the stream was as

           low as 5.2. Water at this pH is considered to be fairly acidic          10

           and can be stressful to many aquatic organisms (Baker et al.,

           1990). There is very little historical information on pH in

           Jabez Branch and it is unknown at this time if the relatively low

           pH recorded during the stream survey is a recent phenomenon or if

           it is a longstanding characteristic of the stream. Of the 3

           species of trout common to Maryland, brook trout are the most

           tolerant of low pH waters (Baker and Christensen, 1990; Baker et

           al., 1990, Johansson et. al., 1977).



                In addition to pH levels varying along the stream's length,

           the pH of the stream also fluctuated during rain events.

           Continuous monitoring of pH near the mouths of the left and right

           forks indicates the pH of the stream can drop as much as 1 pH

           unit shortly after the beginning of the rain event. It is

           unclear if the initial drop in pH at these stations is due to the

           transport of a slug of more acidic water from upstream, or if the

           pH of the runoff generated at the beginning of the rain event was

           more acidic. Additional monitoring of pH in other sections of

           the stream will be needed to examine this question.









           Future Work



                overall, the results from the 1990 monitoring of Jabez

           Branch has provided information on the temperature coming from

           different sections of the stream's watershed. In order to

           determine'the individual contribution that each subdrainage basin

           is having on temperature downstream, not only the temperature of

           the runoff, but also the volume and rate at which the runoff

           moves downstream must also be taken into consideration. In 1991,

           additional work will be done to determine the amount of runoff

           comin q from the different sections of the watershed. A Soil

           Conservation Service TR-55 runoff model has already been

           completed by the Maryland State Highway Administration for the

           upper left fork of Jabez Branch. This model will be modified

           using data collected from our land use surveys to provide an

           initial estimate of the volumes of runoff originating from

           different sections of the watershed. In addition, field

           monitoring in Jabez Branch-in 1991 will concentrate on measuring

           runoff volumes from the different subdrainage basins.











                               LITERATURE CITED

          Bachman, Robert A., personal communication. Chief of  Freshwater
              Fisheries Program, Maryland Department of Natural Resources.
              Annapolis, MD.

          Baker, J.P., D.P. Bernard, S.W. Christensen, M.J. Sale, J. Freda,
              K. Heltcher, L. Rowe, P. Scanion, P. Stokes, G. Suter, and
              W. Warren-Hicks, 1990. Biological effects of changes in
              surface.water acid-base chemistry.
              State-of-Science/Technology Report 13. National Acid
              Precipitation Assessment Program, Washington, D.C.

          Baker, J.P. and S.W. Christensen, 1990. Effects of acidification
              on biological communities in aquatic ecosystems. In: D.F.
              Charles, ed. Acidic Precipitation and Surface Water
              Acidification: Regional Case Studies. Springer-Verlag,
              New York.

          Barry, Edwin M., 1958. Maryland trout report. Maryland
              Commission of Fisheries, Inland Fish Management.

          Johanessen, N., P. Runn and G. Milbrink, 1977. Early development
              of three salmonid species in acidified water. Zoon 5:127-
              132.

          Powell, Albert M., 1967. Historical information of Maryland
              Commission of Fisheries.






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