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..................................... ................ ........... ............................. ............................... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DIFFUSE SOURCE LOADINGS FROM FLAT COASTAL WATERSHEDS. .ater Movement and Nutrient Budgets FINAL REPORT C 0 A,", 17, k PREPARED BY University of Maryland Horn Point Environmental Laboratories for TD 224 -Maryland Department of Natural Resources M3 Tidewater Administration 1982 L65 . ............................ 1982 .................... .......... ...................... .............................. .......... ............................... DIFFUSE SOURCE L0ADINGS FROM FLAT C0ASTAL PLAIN WATERSHEDS: WATER MOVEMENT AND NUTRIENT BUDGETS FINAL REPORT by Kenneth M. Lomax J. Court Stevenson University of Maryland Horn Point Environmental Laboratories Cambridge, Maryland UMCEES Ref. No. 81-247 HPEL JANUARY 1982 property of CSC Library Sponsor and Publisher: Coastal Resources Division Tidewater Administration Department of Natural Resources Tawes State Office Building, C-2 Annapolis, Maryland 21401 Contract No.: CIO-79-430; Preparation of this report was partially funded by a grant from the Office of Coastal Zone Management, National Oceanic and Atmospheric Administration. U .S. DEPARTMENT OF COMMERCE NOAA COASTAL SERVICES CENTER 2234 SOUTH HOBSON AVENUE CHARLESTON , SC 29405-2413 ACKNOWLEDGEMENTS We would like to thank W. S. Christy and M. Yaramanoglu for expertise in interpreting groundw ater movement as well as J. Ayers for his design of the network of wells in the Horn Point watersheds. J. Todd and L. Lane maintained the equipment, collected samples and ran the laboratory analysis. R. Wade, T. Schueler and T. Robbins provided agri-cultural information necessary for the mass balance calculations. Finally, we also appreciate the patience of J. Gilliard and 1. Marbury in preparing tables and in typing the manuscript. TABLE OF CONTENTS Executive Summary 1 Introduction 2 Choptank River Basin Characteristics 4 Background of Horn Point Watersheds 11 Methods Water Budget 16 Determination of Surface Flows 18 Determination of Groundwater Flows 20 Nutrient Concentrations 21 Agricultural Practices 23 Results 26 Discussion Surface export 46 Groundwater concentrations .53 Diffuse source loadings in the Choptank Basin 54 Future Research 62 Management Options 66 Literature Cited 69 Appendices LIST OF TABLES Page 1 -Physical characteristics of selected river systems in Maryland 5 2. Comparative water quality of selected river systems in Maryland in 1970's 7 3. Aerial coverage (hectares) of soil types in the two lower counties of the Choptank River Basin 9 4. Soils of uplands and terraces of the Choptank River Basin on Maryland's Eastern Shore 10 5. Land use in four segment s of Choptank River Basin (hectares) 12 6. Monthly preci tation at Horn Point Environmental Laboratories VEL) in centimeters 27 7. Pan-evaporation data at Horn Point Environmental Laboratories (HPEL) cm per month 28 8. Storm event data at Horn Point Environmental Laboratories from August 1978 through August 1979 29 9. Monthly surface water discharge of nitrogen and phosphorus from agriculture watershed, HPEL 31 10. Monthly surface water discharge of nitrogen and phosphorus from woods watershed, HPEL 33 11. concentration values for agricultural watershed, HPEL 34 12.. Concentration of selected components for woods watersheds, HPEL 35 13. Summary of nutrient conentrations in two well transects at HPEL, 1978-1979 - 39 .14. Dissolved export rates (kg ha-1 yr- 1) from basins with varying degrees of development 47 15. Mass balance calculation of inputs and outputs of nitrogen and phosphorus in the Horn Point agricultural watershed during 1979 50 IV LIST OF TABLES (continued) 16. Mass balance calculation of inputs and outputs of nitrogen and phosphorus in the forested watersheds at Horn Point during 1979 51 17. Nutrient export rates (kg ha-1yr-1) associated with various crops and forested watersheds 52 18. Total nitrogen and phosphorus flux of upper Cho tank north of USGS Greensboro Gage (drainage area = 293 N) for water year 1979 56 19. Estimated nitrogen and phosphorus non-point loadings from various land use types in Choptank Basin 57 20. Estimated municipal discharge of nitrogen and phosphorus in the Choptank Basin in the late 1970's 58 21. Comparative nitrogen and phosphorus loadings associated with major Choptank River segments 59 V LIST OF FIGURES Page 1. Map of the study area showing sites of agricultural and forest flumes 13 2. Graphical description of water movement 17 3. Diagrammatic representation of flow measuring-and sampling apparatus in the HPEL agricultural and forest watersheds. 7000 D.R. = Stevens 7000 digital recorder; 61R TF = Stevens 61R totalizing flowmeter; Type F = Type F stage level recorder. 19 4. Classification of sediment types below the top horizon at the Horn Point study site. 21 5. Map of HPEL study site showing man made features and crop locations in agricultural watershed. 25 6. Location of well transects used for groundwater nutrient study. 38 7. Time variation in nitrogen concentration at the two wells nearest the estuary at the end of each transect, HPEL, 1978-1979. 40 8. Nitrogen concentrations in groundwater along east transect, mean values for 1978-1979. 41 9. Nitrogen concentrations in groundwater along west transect, mean values for 1978-1979. 42 10. Water table contour line showing slope of groundwater toward the woods, HPEL, March 6, 1979 (meters above sea level). 43 11. Water table contour lines showing slope of groundwater toward the woods, HPEL, July 25, 1979 (meters above sea level). 44 12. Yearly nitrogen budget for agricultural and forest watersheds at Horn Point. 63 13. Yearly phosphorus budget for agricultural and forest watersheds at Horn Point. 64 EXECUTIVE SUMMARY A study of dissolved nutrient loadings from predominantly agricultural and forested watersheds on the Eastern Shore of Chesapeake Bay reveals that approximately 10 kg nitrogen (N) ha-1yr-1runs off from mixed cropland areas while only 0.2 kg N ha-Iyr-1 runs off from non-fertilized forest areas. Dissolved phosphorus (P) runoff is about 0.9 kg P ha-1yr-1 from cropland and 0.2 kg P ha-1yr-I from forested areas. These rates indicate that agricultural loadings.significantly increase the ratio of nitrogen to phosphorus concentration*in receiving tributaries (mostly due to high nitrates). Because particulate concentrations of N & P were not measured, the above watershed loading rates are conservative (i.e., underestimates). Subsurface groundwater inputs are quite variable and difficult to quantify, but generally appear to be insignif- icant compared to surface runoff from ditches. However, large concentrations of nitrate (2-12 ppm) were found in the groundwater near the Bay and maylbe transported during periods of extended precipitation to the estuary. In the Choptank River, the largest tributary east of the Bay, calculations show that diffuse sources account for at least 78% of the total N loading (1500 metric tons) and at least 62% of the total P loading (275 metric tons). The implication of this is that in tributaries such as the Choptank, more efforts must be made to understand and control non-point sources. Although advanced treat- ment of effluent from sewage treatment plants (STP) in large municipalities (Easton and Cambridge) would probably make an impact 2 on the water quality of downstream segments, the upper segments of the Choptank are dominated by agricultural runoff. Thus advanced treatment in STP at small upstream towns would be inconsequential in terms of nutrient load reductions in the upper Choptank subestuary. Therefore, in order to improve water quality of non-urbanized Eastern Shore subestuaries, we must focus increasingly on agricul- tural practices which minimize nutrient runoff e.g., no-till cultivation, grass buffer strips along fields adjoining the Bay, and winter cover crops. 3 INTRODUCTION The water quality of the Chesapeake Bay is a prime factor in the maintenance of the present Chesapeake Region economic system and its supporting ecosystem. Declining water quality impacts directly not only on recreational and commercial'activities but also detracts from the image of the Bay as a healthy productive ecosystem. Several agencies of state and federal government have been charged with monitoring and maintaining standards of water quality for the Bay and its tributaries. These agencies have in the past been effec- tively concentrating their efforts on regulating inputs to the various tributaries of the Bay from point sources (i.e., industrial, commercial and municipal outfalls) in order to manage water quality. However, there are suggestions that nutrient loadings from non-point or diffuse sources (such as agricultural wastes, storm runoff, and seepage from poorly operating septic field systems) may be as much as a magnitude greater in rural areas than loadings from point sources such as sewage treatment plants (STP) (Wallace et al. 1972). Previous estimates of the pro.portion of Chesapeake Bay pollu- tion attributable to non-point sources were highly speculative due to the lack of runoff data from the eastern shore coastal plain region of Chesapeake Bay, the richest agricultural area in Maryland. Unfortunately marked differences in slope, land use patterns and agricultural practices between the rolling topography of Chesapeake Bay's western shore and the flat terrain of the eastern shore, make extrapolation of runoff loading rates to the entire Bay from one site a tenuous proposition. Therefore, to estimate non-point inputs to the eastern shore tributaries of Chesapeake Bay, an extensive 4 data set is necessary (including both water movement and water quality) from typical eastern shore watersheds. The critical issue we have addressed concerns the relative magnitudes of diffuse source pollutants from various land use patterns in the Chesapeake Bay region. Hopefully, the results of these studies will be instrumental in determining the extent that efforts should be made by government agencies to limit point source pollution sources in rural basin areas around Chesapeake Bay. If non- point source loadings greatly exceed that from point sources, it makes little sense to spend millions of dollars to install expensive nutrient removal technology at the numerous STP. Instead, more attention should be directed to understanding and minimizing diffuse sources of pollution. On the other hand relatively small diffuse source loadings would indicate that upgrading of STP with phosphorus and/or nitrogen removal might be cost effective in terms of im- proving water quality. In order to quantify the magnitude of diffuse source pollution inputs into particular sub-watersheds of Chesapeake Bay, data is required from areas representing major topographic, hydrologic and land use units. We have been studying several watersheds within the Choptank River basin, an area which is characteristic of much of the eastern shore of the Chesapeake Bay. CHOPTANK RIVER BASIN CHARACTERISTICS A comparison of the physical characteristics of major river systems in Maryland (Table 1) shows that the Choptank is the largest river of the eastern shore in terms of volume and navigable reach. MIMMMM mom MMM MOMIM ml@ TABLE 1. Physical characteristics of selected river systems in Maryland Total Total Intertidal Diffuse basin Navigab e Land Total MLW estuarine sources areaa leng* Drainagea estuarine volume volume loading: (includ area area dilution water) km sq km 106 m2 jo6 m3 106 m3 ratio sq km M2/m3 Chester R. 1,036 61 834 202 835 81.7 1.0 Eastern R. 518 14 292 226 1045 74.4 .3 Choptank R. 2,246 93 11880 366 1441 156.3 1.3 Nanticoke R. 2,111 54 2,036 75 190 52.9 10.7 Wicomico R. 619 16 572 47 107 134.3 5.3 Pocomoke R. 2,300 51 1,913 387 1073 252.0 1.8 Sassafrass 290 24 253 37 158 -- 1.6 Patuxent R. 2,409 86 2,272 137 659 58.6 3.4 Potomac R. 8,664 158 7,413 1,251 7288 241.7 1.0- aMaryland Department of Natural Resources Water Resources Administration Basin Plans bCronin and Pritchard 1975. 6 The main stem of the Choptank extends 107.8 km from its mouth (delineated by Blackwalnut and Cooks Points) to the Delaware State line. The river basin has a total area (including water surfaces) of 2,246 sq km (867 square miles.). In terms of potential influence of diffuse sources, the Choptank River is in the median range with a diffuse source ratio of 1.3 (m2m-3 ). This ratio is an index of dilution potential balanced against potential diffuse source inputs and is obtained by 2 dividing surrounding land drainage (1,880 km ) by the mean low water volume (1441 x 106m3) of the river. Although this value does not take into account different land use patterns or the relative flushing characteristics of each of the subestuaries, it is useful as a first approximation of the relative influence of diffuse source inputs from the land per unit volume (dilution potential) of each river system. The influence in terms of land forcing functions is much greater in areas having a large ratio. Since the Choptank ratio of 1.3 is in the median range of watersheds it is a par- ticularly representative basin for the investigation of diffuse source loadings on the eastern shore. The water quality of the Choptank River is also quite typical of the major eastern shore rivers (Table 2). Levels of chloro- phyll a, coliform bacteria, nitrogen and phosphorus are rather modest considering the relatively high discharge (approx. 10 MGD) from municipal sources. However, the Choptank's large volume (Table 1) produces much greater dilution potential than smaller rivers such as the Wicomico River which receives lower inputs, but has very poor water quality (Table 2). Therefore, because of its large size and 7 TABLE 2. Comparative water quality of selected river systems in Maryland in 1970's. Aver.a Mediana Aver. Total a Inorganica Approximate chl a Fecal Phosphorus Nitrogen Point Coliform Discharge mg l-, MPN jjg 1-1 jjg 1-1 MGD Sassafrass R. 70 90 81b 579d Chester R. 50 - 31 949c .57 Eastern B. 37 - 149 439d .04 Choptank R. 74 800 229 526d 10.04 'Nanticoke R. 54 160 81 935 1.19 Wicomico R. ill 1500 399 3164 4.00 Pocomoke R. & S. 46 730 480 916 .73 Patuxent R.e 147 2100 4100 -- 24.54 dValues are not average for the entire river but means of segment having highest concentrations. All data from Maryland Resources Administration "Maryland Water Quality 1975", Department of Natural Resources bTotal phosphate CN02 + N03 dNitrate epatuxent data from EPA Tech Report 58 (1973) 8 typical loading patterns, the Choptank River watershed is an ideal area for the study diffuse source and point source loadings on a highly agricultural flat coastal plain. The soil series in the upper Choptank (Fincher 1976) consists of the following: Pocomoke 38%, Fall-sington 25%, Sassafras 18%, Woodstown 6%, Rumsford 5%, Evesboro 4%, minor soils 4%. A detailed listing of types in the lower basin, more representative of our study area, is presented in Table 3. Drainage problems are associ- ated with the Pocomoke, Fallsington and Woodstown soil series (see Table 4). Because of poor overall topographic relief, these soils are prone to be problematic for agriculture unless drainage ditches are utilized. However, corn yie Ids can be comparable to that of the midwestern U.S. corn belt ( 160 bush/acre) on the Sassafras and other rich upland soils where drainage problems are negligible. In the higher elevation areas of the Choptank wate@shed in Queen Anne and Talbot Counties the highest corn yields in the state of Maryland are often reported. Poor drainage in low lying fields can result in protracted periods of waterlogging producing anaerobic soils. In addition to stresses induced to crop-plants from oxygen depletion, dentrifica- tion may occur when soil carbon levels are high (Denmead et al. 1979, Firestone et al. 1979, Terry and Tate 1980). High dentrifica- tion rates can result in a substantial loss of nitrate in field soils causing reduced fertility. This was apparently the case in the wet spring of 1979 when there was considerable rainfall just after planting. Therefore, variable amounts of nitroge n in the fertilizers are lost into the atmosphere immediately after application. Thus, 9 TABLE 3. Aerial coverage (hectares) of soil types in the two lower counties of the Choptank River Basin. Soil Type Dorchestera Talbotb Total % Total County County AGRICULTURAL SOILS Barclay 3,995 3,395 2.16 Bayboro 2,212 2,212 1.19 Bibb 79 79 .04 Downer 1,089 1,089 .59 Elkton 10,202 10,202 5.51 Fallsington 9,146 3,824 12,970 7.00 Galestown 5,483 285 5,768 3.11 Johnston 390 390 .21 Keyport 2,782 5,455 8,237 4.45 Klej 2,258 130 2,388 1.29 Lakeland 765 765 .41 Matapeake 3,826 5,177 9,003 4.86 Mattapex 5,317 7,298 12,615 6.81 Othello 15,622 719 16,341 8.82 Plummer 269 40 309 0.17 Pocomoke 2,634 170 2,804 1.51 Portsmouth 664 145 809 .44 Sassafras 20,460 15,838 36,298 19.60 Woodstown 6,471 5,574 12,045 6.50 BORROW PITTS 157 157 .08 COASTAL BEACHES 86 47 133 .07 MADE LAND 34 282 316 .17 MIXED ALLUVIAL 816 1,980 2,796 1.51 STEEP LAND 904 904 .49 SWAMP 7,047 7,047 3.80 TIDAL MARSH 33,060 2,478 -35,538 19.19 119,421 65,789 184,610 100% aMathews, 1963 bReybold, 1970 TABLE 4. Soils of uplands and terraces of the Choptank River Basin on Maryland's Eastern Shorea Somewhat Moderately Very Poorly Parent Material Excessively Well Drained Well Drained Poorly Drained Drained Drained Sand and loamy sand Galestown Klej Plummer Rutlege Lakeland Sand, silt and clay 'Sassafras Woodstown Fallsington Pocomoke Mantle of silt over sand Matapeake Mattapex Othello Portsmouth Clay or silty clay Keyport Elkton Bayboro SOILS OF FLOOD PLAINS OR BOTTOM LANDS Sand, silt and clay Bibb Johnston aMathews, 1963 M Aw 00 'am as no law an there are questions concerning the fate of nitrogen in fertilizers in any particular year. Denitrification rates of from 5 to 50 percent have been reported for a wide range of agricultural prac- tices (see Nielson and MacDonald 1978). It is of utmost significance whether the nitrogen from fertilizers used in farming activities on the eastern shore ends up in Che@sa'peake Bay, in the atmosphere, or is lost to groundwater. The land use statistics for the upper and lower Choptank Basin are shown in Table 5. The most extensive use is agriculture (66%) with forested land being the second most important category (29%). Urban areas with commercial and residential development presently comprise a relatively small fraction (4%) of the land use, while the marsh interface which buffers the Chesapeake Bay is less than 1% of the land area. Therefore, analysis of the land use pattern reveals that approximately 95% of the surface area (above mean high water) can be accounted for with projected data from forested and crop land in the Choptank watershed. BACKGROUND OF HORN POINT WATERSHEDS Three watersheds draining into LeCompte Bay, Dupont Cove and Lakes Cove were chosen for the study of diffuse source inputs to the Choptank River watershed (Figure 1). All of these watersheds are situated on the 850 acre (3.44 sq km) campus of the Horn Point Environmental Laboratories, a branch of the University of Maryland Center for Environmental and Estuarine StudiRs. This area was originally patented in 1659 and was undoubtedly cleared for the planting of tobacco soon after. The remains of a 12 TABLE 5. Land use in four segments of Choptank River Basin (hectares)c Land Lowera Upper b Tuckahoec Delaware Use Choptank Choptank Creek Segment Total Agriculture 32,916 42,390 28,978 11,631 115,915 Forested 11,591 18,353 10,848 9,591 50,383 Development 3,344 1,746 ill 1,864 7,065 Marshes 483 929 0 0 1,412 48,334 63,418 39,937 23,086 174,775 adownstream town of Choptank (includes Hunting Creek Watershed) bupstream from town of Choptank to the Delaware line ccompiled from Solyst and Davidov 1979 (Md) and Fincher 1975 (Del) 13 HORN POINT LECOMPTE BAY 04 LAKE'S W\FO R E S T COVE FLUME AGRICULTURAL DuPONT FLUME COVE VL SceLle- IV% MaIr-5 Figure 1. Map of study area showing sites of agricultural and forest flumes. 14 brick house dating from the late 1600's adjacent to Dupont Cove (Figure 1) indicate a rather impressive plantation in this area over 300 years ago. In the 1700's vacillating tobacco prices and in- creasing impoverishment of organic matter in soils caused farmers to shift to less nutrient demanding crop species. Wheat and corn became the principal crops in the area by the late 1700's and continued to be extensively planted in the 1800's. In the early twentieth century many farmers began using inorganic fertilizers and diversified their farming operations to include vegetables which were canned in the nearby town of Cam- bridge. A resident of the area remembers when the watershed which is now entirely a pine forest supported a tomato farm, a common cash crop in the early 1900's. When T. Coleman Dupont purchased Horn Point in the 1920's, he restored a major portion of the property to forest and loblolly pines were planted over most of the watershed. Thus, the forested area of our study has not been fertilized in any way for over 50 years. The pines have been systematically cut in various portions of the watershed since then. The USGS map of 1942 shows that the central portion of about one-quarter of the watershed was not forested at that time. Also, an aerial photograph from a conservation plan reveals that the southeastern portion of the watershed was thinned in the 1960's. In addition to selective cutting, Rhus radicans vines have taken over much of the canopy. This makes it known to those who have had to spend extensive amounts of time sampling in it as a "pine-poison ivy" subclimax forest. A few hardwood species are in the shrub layer, but seldom has succes- sion progressed far enough to have these transgressive species in 15 the canopy. The I m deep ditches in the watershed were undoubtedly dug when the area was still under cultivation to help relieve the high water table conditions. The crops now regularly planted in the agricultural watershed consist of three species: corn, small grains (wheat or barley) and soybeans. These are planted in a 2-year rotation described in detail in the methods section. This is presently the typical sequence of cropping on the Delmarva Peninsula. Thus the Horn Point runoff data should have wide applicability to many sites on the eastern shore of Chesapeake Bay. 16 METHODS The first factor in estimations of watershed loading rates is the quantification of the runoff component within the overall water budget of the study area. The second includes the periodic measurement of con- centrations of materials of interest (nitrogen and phosphorus in this case) contained in the runoff. Our approach to measuring each of the above factors is detailed below under respective sub-divisions fol- lowed by a description of agricultural practices carried out at Horn Point during this study. WATER BUDGET Waterborne materials move from the land to the estuary either through surface or groundwater flows. These two flows are part of the larger hydrologic cycle of the low flat coastal areas around Chesapeake Bay which needs to be quantified for an accurate assessment of diffuse- source pollution. Precipitation is either intercepted by vegetation such as crop or forest canopies or bare ground. After the rain hits the land it may move across the ground surface or soak into the soil depending on the previous fi-eld moisture levels. Most of the precipita- tion is returned to the atmosphere via evaporation or transpiration. Some of the soil moisture moves to deep aquifers, but most of it moves laterally through the soil to eventually reach ditches, streams or the estuary. Main pathways are depicted in Figure 2 from Daniels, et al. (1976) where the line width approximates the relative annual volume of water in that direction. Components of the water budget which require field measurements 17 DISPOSITION OF RAINFALL ON 0 A NEARLY LEVEL COASTAL PLAIN. SURFACE C9 -R n o f f Aqu'ifer Leakage Deep Aquifer Recharge Figure 2. description of water movement.' 18 are precipitation, interception, surface flow, groundwater levels, and moisturd. These measuremen ts. in combination with calculations for evapotranspiration and groundwater flow will roughly describe the water budget. Measurements of precipitation, surface flow, an'd groundwater levels are report ed below with additional details using 0":0" methods available in Christy 1980. Determination of Surface Flows The surface flows were measured at the mouths of the watersheds by Parshall flumes installed in existing drainage ditches. Selection of Parshall flumes as the measuring devices was based on their ability to remain accurate with a relatively high percentage submergence, a problem in low flat coastal plain areas (Lomax et al. 1980). For example, Parshall flumes will remain accurate to 70% submergence and only need a 5% cor- rection in head fo r 80% submergence. Also they remain clear of debris which often catches in V-notch weirs giving erroneously high water flow estimates. Flow meter/water sampling instrumentation was calibrated by the manufacturer (Leopold & Stevens) for standard prefabricated three-foot Parshall flumes (Fisher & Porter Co., Towson, Md.). At 15-minute intervals, a punch tape recorded the head in feet (Stevens Model 1001), providing 6 digital record of the height of water on the inlet side (ha) of the flume. Also on the inlet side, a Stevens totalizing flow meter with stripchart recorder (Stevens Model 61R), triggered the sampling pump. (See Figure 3.) To correct the head and flow meter records for submerged conditions, *the outlet or downstream head (hb) was recorded with a Type level 19 PARSHALL FLUME Sectional View Flow Crest Flow 3 ha hb PLAN VIEW 61R 7000 TF DR Type F Sampling INSTRUMENT Pump and SHED Storage 74 000 DR Sam 3n p Iig Pump and Sto ra ge Figure 3: Diagramatic representation of flow measuring and sampling apparatus at the Parshall flumes installed in the HPEL Agricultural and forest watersheds. 7000 DR= Stevens 7000 digital recorder; 61R TF=Stevens 61R totalizing flowmeter; Type F=Type F Staqe level recorder. 20 F-recorder (Leopold & Stevens). If the outlet head was less than 70% of the inlet hea'd, no submergence adjustments of the upstream hydro- graph were necessary for determination of flows. For submergence values between 70% and 100%, standard corrections for Parshall flumes were used to obtain the equivalent inlet head without submergence. The surface water flow records were more complete for the agricul- tural watershed than for the woods watershed because of instrument failures. Despite the instrument problems encountered during flume flow measurements, sufficient reliable data were obtained to calculate a yearly budget. Base flow rates were often less than critical for this flume size, requiring an estimation calibration of the flow when the head was lower than 3 cm. (There was insufficient variation in base flow to have much effect on the accumulated runoff). Determination of Groundwater Flows Groundwater movement was calculated from water table measurements and a detailed sediment mapping from the grid of 290 shallow wells at HPEL. Ten cm (4 in), thin-walled P.V.C. pipes were installed in 10 cm (4 in) hand-augered bore holes. Upon completion of the bore hole, the sediments usually maintained enough integrity for pipe insertion and were sealed with clay around the upper portion of the casing. When encountering saturated sands, the hole walls tended to c ave in and normal augering became impossible. In this instance, the P.V.C. casing was pushed down into the sands as far as possible. An 8.3-cm (3.1@4-in) sand auger was then inserted down the inside of the casing to bail out the sands. In some cases, wells were sunk as deep as 2.9 m (%2 ft) using this method until encountering an underlying tight 21 sedimentary layer. In order to prevent temporarily ponded water from flooding the well, at least 10 cm (4 in) of the P.V.C. pipe was left above the ground surface. In areas of known ponded water extensions were added so that the pipes were above the average ground level by 30 cm (I ft) or more. Each well top was capped with P.V.C. plugs to exclude precipitation. The sediment map (Figure 4) was developed for the 1-3 m deep sedimentary horizon from the drilling logs recorded for each ground- water well. Each location was classified into one of the four categories. Shallow sand indicated that a sandy stratum at least 0.3 m (1 ft) thick was found within 1.5 m (5 ft) of the ground surface. When a profile lacked a sandy stratum, but contained layers of sand and silt intermixed, then the location was designated Sand/Silt. The Deep Sand category indicated a sandy stratum starting below 1.5 m (5 ft) and con- tinuing at some places below 3.0 m (10 ft). Grain size was generally larger for deep sands than for shallow sands. When a profile showed uniform silt with no extensive sand it was categorized as Silt. NUTRIENT CONCENTRATIONS Triggered by the flow meter instrumentation in the flumes, samples of the flowing water were taken at intervals equivalent to 150,000 liters of discharge. The volume-integrated samples were collected weekly and subsampled for laboratory analysis. Additionally, grab samples of surface water were analyzed for nutrients. Ground water samples were taken from selected wells on a biweekly schedule and analyzed immediately in the laboratory. The laboratory procedures for nutrient concentration were L 6 -aj@s Xpnjs JULOd UJOH aq4 42 UOZLjoq dol @141 MOLaq sadki IU@WLP@S 10 UOL41120LJ@ssPLO -t, ajn6Lj 7 ............. Ut, L;. 'If rill. 11 at 44:@ 0 till", Ap 't@@ :.4, rf-, V, W 4:i:, V" @ ar ed @ - : . , . ,:! IP IV. ."T n 4: r ig Lip, JP@O; - . -yj -IpI '@:, ., "Iff -;tl igl. h iq N - - - 41 'k,"; I':, L. "it P P..s d_(j "V..I. ., , of! 4.:N It 'ilkI s$ "R. "uh 4'L 4.11 I It .13 ". . P.-S -.11-4111 If 4,fil M. -Ali..4 if of 00" @T All 411 -f I. @ , Ill, "I Oft. 104, .111'. 111 191 lots rd 'A .11 1, 7/0@1 �R` lj@j -,h, I., L !N@ I + a 3P 7' Y- @O 0 41 it, :j,,,qpr I/ I I -Ij;,.qI1IIlIIlIb * I X 911 It'll. 41,4 I.N1 OF V Z, S) u a w I Pa S "A 'all fill qt - 3111,41 OutI Vill -4,11m!J11. All N, u lilt -:j 1 If 7Z -x, %1 '7 -fir :,40 A,Ail ? IF;, 4 It J, If Ihgl@, qk 1r) -:2 :A1, - :d . 0 00S 10 23 carried-out as follows. Nitrate and nitrite nitrogen were determined by cadmium reduction of a filtered sample followed by colorimetric measurement of nitrite (APHA, 1975). Nitrite nitrogen was measured on a filtered (pore size = 0.45 micron) sample prior to reduction of the nitrate to nitrite. Ammonia nitrogen was determined colorimetrically by a modified phenol-hypochlorite technique (Strickland and Parsons, 1972). Orthophosphate was determined on a filtered sample by the ascorbic acid method (APHA, 1975). The total phosphate concentration was measured after persulfate digestion of a whole sample by the orthophosphate pro- cedure. Chloride ion concentration was determined by the argentometric method (APHA, 1975). AGRICULTURAL PRACTICES During the initial phase of diffuse source pollution research at Horn Point, tenant farming continued without alteration of cultivation practices common to this region. The majority of farmers on the Eastern Shore of the Chesapeake Bay rotate their crops over a two year period. Corn is planted the first spring and harvested in early fall so that small grains (i.e., wheat, barley or millet)-can be pl-anted that fall. When the small grains are harvested in early summer, soybeans are planted in the stubble without plowing using a contact herbicide to control weed populations. After soybeans are harvested in late fall, the land is not usually cultivated again until the following spring when corn is again planted. Fertilizers are applied at various times of the year depending on which crops are being planted. Figure 5 shows that of the 86 total hectares in the agricultural watershed, 54 hectares are cropland with predominant coverage in soybeans b 0 V, I Doo' z WAT E RSHEDS F-I All- Agr icu It vre Morsh Wood s so. S b* C IIf S S S S N' It Z* S %% IN S 61 4P -1 . . . . . . . . . K E Y Ditches F I u m e Buidings 0 0 oe .It \Pt ...k- Figure 5. Map of HPEL study site showing man made features and crop locations in agricultural watershed. Crop symbols 1979:- C = corn,-S = soybeans, H = hay. 25 during 1979. Soybeans were planted in 37 ha, corn in 7 ha, and hay in 10 ha. In general, the farming operations at HPEL are standard agricul- tural practices recommended by the Cooperative Extension Service for heavy soils in low lying areas on the Eastern Shore. The corn was fertilized at planting using 357 kg/ha (400 lbs/acre) of 5-20-30 (N:P:K). This rate is equivalent to 18 kg N/ha nitrogen (20 lbs/acre) and 71 kg P/ha phosphorus (80 lbs/acre). At about eight weeks, the corn was booster-fertilized with anhydrous ammonia at 135 kg N/ha (120 lbs/acre). The soybeans received much less nitrogen of 268 kg/ha (300 lbs/acre) of 5-20-30 at planting. The portion of watershed planted in soybeans had an equivalent of 13 kg N/ha nitrogen (15 lbs/acre) and 54 kg P/ha phosphorus (60 lbs/acre). The red clover hay crop was fertilized with an application of 268 kg/haw (300 lbs/acre) of 10-20-20 at planting. Of the remaining 32 ha, in the agricultural watershed, approximately 25 ha were forested with the remaining 7 in miscellaneous categories such as grass and roads. 26 RESULTS Precipitation records (Table 6) indicate that the n on-point source studies at Horn Point were begun in the relatively dry year of 1976 and continued until the relatively wet year of 1979. When precipitation is corrected for evaporative losses from the soil surface to obtain an indication of soil moisture charge and dis- charge patterns, both 1976 and 1977 are obviously,years in which no net recharge occurred (Table 7). The resulting low water tables were monitored using the well system in the latter part of 1976. Recharge occurred in 1978 (29 cm) and 1979 (71 cm) because of increased. precipitation which also produced ample runoff events. High intensity, high volume precipitation events provide overland flow or quick flow. Those storms which exceeded 1.8 cm (.70 inches) during 1979 are listed in Table 8. This storm size was selected to show the temporal variation in rainfall events which would most likely provide overland flow. Some of these storms provtded so little quickflow that the gradual rise and fall of the hydrograph did not show any overland flow period. The soil moisture indication on Table 8 was obtained in relative terms from the water table depth and the time since the previous rain. Surface water discharge on a monthly basis was calculated from flume head measurements. Both the upstream and downstream heads were used to calculate the flow rate,of water leaving the watershed for each storm. A sample analysis and hydrograph is shown in Appendix A. During all of calendar year of 1979, there was surface discharge continuously from the agricultural watershed. Taking into account 27 TABLE 6. Monthly precipitation at Horn Point Environmental Laboratory (HPEL) in cent imeters DATE YEAR MONTH 1973 1974 1975 1976 1977 1978 1979 January - 7.3 13.4 11.8 5.9 19.3 15.6 February 4.3 6.1 2.9 2.3 3.1 18.2 March - 13.0 12.1 6.4 4.7 18.7 8.5 April - 3.6 9.9 0.7 5.6 8.9 8.4 May - 15.9 10.4 7.7 10.5 14.5 9.9 June - 10.0 17.7 1.5 9.1 7.9 8.4 July - 2.4 17.5 9.1 4.6 16.6 19.4 August - 17.9 9.6 3.9 10.1 13.2 23.4 September - 7.3 19.9 8.4 9.3 1.3 17.4 October - 1.9 8.4 16.1 9.5 2.9 11.7 November 4.7 3.1 7.4 3.5 10.4 7.2 10.2 December 10.5 12.5 10.2 6.9 15.5 9.8 4.8 Yearly - 155.9 Totals 99.0 142.44 79.0 97.6 123.5 28 Table 7. Pan-evaporation data at Horn Point Environmental Laboratory (HPEL) cm per month, MONTH 1975 1976 1977 1978 1979 March 'UO 6.2 1.3 3.6 April 12.3 11.2 10.5 8.4 May 13.7 .12.5 12.9 10.5 12.6 June 14.8 15.9 14.2 15.2 13.2 July 12.3 15.9 16.5 14.9 13.4 August 15.7 14.9 15.1 14.4 13.3 September 7.7 10.2 10.9 10.5 8.9 October 6.4 6.3 7.0 8.8 7.2 November 5.3 4.5 4.6 6.3 4.3 December 1.6 -"0 1.0 2.2 %0 @Yearly Totals 77.6 92.5 98.8 94.5 84.9 net chargea discharge +23.0 -13.5 - 1.2 +29.0 +71 aTotal Precipitation (Table 6) minus pan-evaporation. Plus (+) indicates net charge and minus (-) indicates net discharge. 29 TABLE 8. Storm event data at Horn Point Environmental Laboratory from August 1978 through August 1979 DATE Precipitation Total Duration Prestorm Soil (CITO (Hours) Condition 8/2/78 2.1 2.5 Wet 8/3 1.8 2 Wet 8/5-6 1.9 18 Wet 8/31 4.9 10 Dry 11/26-27 2.4 15 Dry 12/4-5 2.7 9 Wet 12/9 1.9 12 Wet 1/1-3/79 4.4 - Dry 1/20-22 5.1 Frozen 1/24 2.8 - Wet 2/18-19 4.6 10 Frozen 2/24-26 10.7 32 Wet 3/5-6 3.5 36 Wet 3/11 1.8 9 Wet 3/24 2.3 6 Dry 4/3-4 2.6 48 Dry 4/26-27 3.2 - Dry 5/25 4.5 - Wet 6/4 2.5 - Wet 6/11 4.6 - Wet 7/1-2 5.8 - Wet 7121 2.6 - Dry 7/24 2.7 - Wet 7/29-30 6.9 - Saturated 8/3 4.5 - Saturated 8/12 4.6 - Wet 8/21 2.9 - Wet 8/28 2.9 - Saturated 8/29 4.6 - Saturated 30 the area of the watershed, the surface discharge is presented in Table 9 with units of centimeters allowing for direct comparison with precipitation data. One of the largest runoff events in the last 30 to 40 years occurred in February 1979 when a relatively large snowfall, equiv- alent to 4.5 cm precipitation, was followed closely by heavy rain on frozen ground. This event caused sufficient surface water flow to cau-se the depth of water at the agricultural flume to exceed the height of the flume 0 meter). That storm sequence was of such a magnitude that it destroyed many small bridges, dams and other structures on small creek's on the eastern shore. From the flume discharge measurements, it was calculated that most of the snow and rain were discharged in the relatively short time of three days. As a result of the soil conditions and the rapid rate of rainfall, the runoff for the month of February is approximately two-thirds of the total precipitation. This event produced the largest percentage of runoff any month on record at Horn Point. The remaining one-third of February's precipitation which was not measured as surface water runoff was lost to the atmosphere (evaporation or sublimation) or lost to the soil and sediment for storage or deep recharge. The twelve months shown in Table 9 are not from the same year but are from three calendar years. To achieve accurate nitrogen and phosphorus discharge values, the months having reliable nutrient concentration data were combined into an idealized model year. Although the idealized model year is composed of non-sequential months, the total precipitation is very close to the expected precipitation for calendar year 1979. The alternative to this 31 Table 9. Monthly surface water discharge of nitrogen and phosphorous from agricultural watershed, HPEL. Nitrate & Nitrite Total Phosphate Precip. Runoff Nitrogen Month Cm cm mgN/k Kg/ha pgP/k__. g /ha Jan. 79 15.6 10.3 2.0 2.0 240 250 Feb. 79 18.2 12.2 1.0 1.2 130 160 Mar. 79 8.5 3.2 1.1 0.4 100 32 Apr. 79 8.4 3.8 1.2 0.4 150 57 May 79 9.6 3.1 5.0 1.5 50 15 Jun. 79 8.4 2.5 0.7 0.2 160 40 Jul. 79 19.4 7.7 0.7 0.5 60 46 Aug. 79 23.4 7.8 0.6 0.5 100 78 Sep. 76 8.4 1.4 0.2 0.0 200 28 Oct. 76 16.1 4.9 0.3 0.1 60 29 Nov. 77 10.4 3.6 0.3 0.1 170 61 Dec. 77 15.5 5.8 0.3 0.2 260 150 TOTAL 161.9 66.3 7.1 946 7.1 Kg N/ha/yr I Kg P/ha/yr 32 approach would be to have only nutrient concentrations without runoff or vice versa. The hydrology of the woods watershed is markedly different from that of the agricultural watershed. Presentation of surface water runoff in length units, that is centimeters, allows for direct comparison of the watershed hydrology, even though the area of the woods watershed is much smaller than that of the agricultural watershed. As shown in Table 10, runoff in February 1979 at the woods flume was almost the same as that from the agricultural flume. Throughout the winter months the runoff from the two watersheds is similar, but the annual total is quite different. The woods water- shed would be expected to have a lower percentage of precipitation appear as runoff because of the increased evapotranspiration rates associated with the forest canopy which would increase water loss compared to the agricultural watershed. The movement of nutrients from the forested and agricultural watersheds to the estuary are presented in Tables 9 and 10. Using these concentrations of N and P presented in Tables 11 and 12 and the runoff measurements, the flux of nitrogen and phosphorus were calculated. Nitrogen discharge from the agricultural watershed in May 1979 appears to reflect the application of fertilizer. The January 1979 discharge is not as easily explained, but probably reflects both reduced winter assimilation of nitrate by vegetation and denitrification as well. Marbury and Stevenson (1980) suggest that ice reduces denitrification substantially during the winter at Horn Point Marsh. Therefore, more nitrate is available for runoff during cold winter months than in warmer months. 33 Table IO.Monthly surface water discharge of nitrogen and phosphorous from woods watershed, HPEL. Nitrate & Nitrite Total Phosphate Precip. Runoff Nitrogen Month cm cm jig.N/z g/ha lig P/2' g/ha Jan. 79 15.6 9.1 50 45 70 64 Feb. 79 18.2 11.8 50 59 20 24 Mar. 79 8.5 3.1 60 19 90 28 Apr. 79 8.4 1.9 0 0 80 15 May 77 10.5 0.2 100 2 40 Jun. 79 8.4 0.5 20 1 100 5 Jul. 79 19.4 2.1 40 8 80 17 Aug. 79 23.4 1.9 10 2 150 28 Sep. 79 8.4 0.4 20 1 100 4 Oct. 76 16.1 2.3 0 0 140 32 Nov. 78 7.2 1.8 90 16 30 5 Dec. 77 15.5 4.8 10 5 40 19 TOTAL 159.2 39.9 158 242 .16 Kg N/ha/yr .24 Kg P/ha/yr 34 Table 11. Concentration vaiues for agricultural watershed, HPEL. Ortho Total Total Total Ni tra te Nitrite Aianon i a Phosphate Phosphate Particulate Dissolved N N N P P Chloride Ma tt e r BOD Solids Date Ij g/I Pg/I JALE I Vg/I mg/I Vg/I mg/I mg/I 04-10-78 136 0 5 25 is 05-16-78 130 1062 07-08-78 136 260 360 38 07-31-78 Go 120 16 08-07-78 132 265 4DO 5 08-14-78 30 50 12 09-01-78 38 11-27-78 1 280 334 4,700 11-27-78 91 1 460 65 80 4.000 12-04-78 13 0 12 117 (11 am) 12-04-78 8 a 30 94 (2 pm) 12-05-78 2 >1.000 165 260 13 (10 am) 01-02-79 2,000 19 3,000 175 210 6 246 124 01-08-79 21 3,000 115 200 11 177 8 230 01-21-79 46 1,640 232 295 8 200 165 01-22-79 2,050 28 >2,000 165 265 13 190 5 257 02-25-79 912 3 106 163 1 02-26-79 1,000 5 360 135 54 1 61 4 49 02-27-79 800 10 710 145 200 4 212 5 392 03-06-79 1.100 20 1.540 185 90 8 235 8 183 Peak Flow 04-04-79 700 6 102 42 10 90 166 End Flow 04-05-79 1,200 16 100 200 17 30 178 05-14-79 5.766 3 0 43 50 05-23-79 7.808 1 0 51 41 Baseline 06-31-79 587 5 18 56 12 06-01-79 570 7 140 47 140 14 26 207 06-04-79 510 7 6? 134 10 161 2 203 D6-11-79 1,145 6 186 16 203 6 1.090 6 134 07-30-79 685 6 29 62 12 68 174 08-13-79 656 3 30 100 9 27 2 195 35 Table 12. Concentration of selected components for woods watershed, HPEL. Ortho Total Total Total Nitrate Nitrite Aninon I a Phosphate Phosphate Particulate Dissolved N N N P P Chloride Matter BOD Solids Date -1'9@1 -- 1jq/1 mq@k mg/t 04-10-78 16 3 10 40 3 05-16-78 130 07-08-78 4 20 80 22 07-31-78 20 90 16 08-07-78 32 20 90 12 08-14-78 20 45 160 49 09-01-78 44 11-17-11 1 50 94 11-27-78* 90 1 690 30 18 4,750 12-04-78 56 9 80 94 3,500 (11 am) 12-04-78 1 57 64 3,000 (2 pm) 12-05-78 7 4 45 68 91 01-02-79 6 2,780 40 70 16 0 214 01-08-79 55 3 3,780 10 35 9 17 5 125 01-22-79 40 16 72,000 5 75 2 2 89 02-27-79 48 4 1,280 10 22 2 63 5 0 03-06-79 58 3,080 9 90 4 9 4 90 04-05-79 6 0 25 84 4 10 130 06-01-79 24 6 28 Interference 12 2 2 139 06-04-79 17 5 Interference 120 2 11 1 145 06-11-79 1 0 245 67 89 2 21 5 41 07-3D-79 38 7 30 78 8 0 108 08-13-79 10 4 51 150 0 32 1 166 *Composite 36 According to calculations and measurements for the agricultural watershed, the runoff at the flume accounted for approximately 42 percent of the precipitation for one year. This percentage value is higher than might have been expected and can possibly be explained by subsurface water movement to the drainage ditch. Characteristics of groundwater movement have been approached in three ways. First, through the use of two transects of groundwater wells; secondly, from data collected on a closely spaced grid of wells; and third, from the entire network of groundwater wells on the HPEL site. Two transects on the study site were selected for more intense observation and sampling. These two transects both originate near the estuary and cross the higher ground toward the next potential groundwater outlet with the intention that the transect will cross the groundwater divide. Variations in water table elevation in the two transects have not been useful in describing groundwater divide or peak from which the water would move one way or the other. The va riation in water table along the transect indicates that the water table divide moves without simple explanation. If this variation could be accounted for, it would require a three dimensional analysis (see Christy, 1980). The elevations have, however, shown that during parts of the year the groundwater is moving in one direction, toward and under the woods, and in the other part of the year it is moving toward the estuary. Groundwater elevations for the entire study site have not been analyzed sufficiently to include a picture of these data. Some significant findings, however, can be mentioned-The groundwater regime is not at all uniform on the study site. There are more 37 valleys and ridges than might be expected for the relatively flat landscape. It has also been observed that the groundwater does not necessarily follow the surface watershed in extent and direction (Christy, 1980). However, Figure 6 shows two transects which give a reasonably accurate representation of the spatial patterns in groundwater quality. The most interesting data collected from the transects are presented in Table 13. These mean values for all available data indicate that throughout the year there is a difference between various parts of the landscape. Perhaps the most striking con- stituent is the nitrate nitrogen. Figure 7 shows the variation in nitrate nitrogen with time at the two wells close to the estuary. Figures 8 and 9 show the nitrogen concentrations as a function of the transect distance. It is rather obvious from these figures that the nitrate nitrogen is higher close to the estuary. This observed phenomenon has several possible explanations (elaborated in the discussion). Other constituents such as chloride do not have an obvious relationship to physical location. Neither lateral distance, depth, nor their interaction, correlate with the chloride concentra- tions. One untested hypothesis is that chloride concentration relates to sediment "cracks", which would provide increased hydrau- lic conductivity. The intense groundwater elevation experiment during the spring and summer of 1979 shows how the groundwater moves toward the wooded area at a rate seemingly related to evapotransporation. As shown in Figures 10 and 11 the slope on the groundwater is flatter in March than it is in July. In July the groundwater slope approaches one 38 Vf. 0 0 5 0 1 000 A.- 1@4 -y"I"A' -@M"@ j 2 r 3 p. i L '27 @35 o r '4a 25 N 'A @3 nz) wK 3 j f -A Q W L) 7 Vegetation ?.4 3 C.Iti-tion Pi.. Plontat,on C., 0- F.-, @Nv r De-d... F.-, _AJ Figure 6. Location of well transects used for groundwater nutrient study. Wells A-2 through W-163 are the east transect. Wells M-52 through W-18 are the west transect. 39 Table 13. Summary of nutrient concentrations in two well transects at HPEL, 1978-1979. (Values are means for all available data.) Nitrate Ortho Total +Nitrite Nitrite Ammonia Phosphate Phosphate Chloride Depth Ii gN/k ljgNIY- jjgN/Y, Pgplk jjqP1k mqcl1k m A-2 4,000 4 130 7 33 50 3.04 A-11 700 5 1140 27 51 45 2.43 A-27 55 6 690 3 30 100 1.77 M-25 800 4 150 20 57 15 3.04 M-34 75 3 800 8 44 20 2.90 M-52 1,600 2 180 17 38 25 1.22 W-16 120 7 1010 11 20 140 3.04 W-18 205 7 320 39 125 535 4.27 W-32 120 4 210 27 63 350 3.04 W-83 340 9 640 62 142 50 1.52 W-84 270 3.0 90 2.90 W-135 120 4 970 .2 22 15 2.90 W-141 35 1 1470 4 27 35 2.90 W-143 90 3 740 4 24 30 2.90 W-144 40 3 310 6 33 50 2.90 W-163 20 10 480 7 32 2.90 (3) 4-) E 4-) 4-) A-2 4--) (0 S- 4--) 3.0- M-52 0.3- AUG SEFT OCT NOV DEC JAN FES -HAR APN-- I MAY JUNE JULY Figure 7. Time variation in nitrogen concentration at the two wells nearest the estuary at the end of each transect, HPEL, 1978-1979. Z: 2.0. 4-) S- 4-) 1.0- 0.5 O'l S 0 E 5 0' 0 -1000 A A A A A A A A-2 A-11 A-2 7 W-135 W-141 W-145 W-144 W-163 Figure 8. Nitrogen concentrations in groundwater along east transect, HPEL, mean values for 1978-1979. S- 4-) 4--) 0.4 4-) 0.1 4-) 0 METERS 560 10,0 Q A A A A M-25 M-34 W-3, W- %6 W-83 8 Figure 9- Nitrogen concentrations in groundwater along west transect, HPEL, mean values for 1978-1979. 4t:- NO 43 N FOREST 0 3.35 0 0 0. 0 0 3AI 0 0 0 0 0 0 0 0 0 0 0 0 tr- 0 0 10 meters -AGRICULTURAL FIELDS Figure 10. Water table contour lines showing slope of ground- \N water towards the woods. Circles represent well locations. HPEL, March 6, 1979 (meters above sea level). 44 N FOREST 0 0 2.87 2.93 0 2.9 0 0 0 0 3.0 3. 0 0 0 0 10 meters AGRICULTURAL FIELDS Figure 11- Water table contour lines showing slope of ground- \N water towards the woods. Circles represent well locations. HPEL, July 25, 1979 (meters above sea level). 45 percent which is significantly different from zero and significantly different from the flat ground surface at the point where these wells were installed. This intense groundwater elevation study substantiates the hypothesis that the groundwater flows away from the estuary even during part of a wet year! Using the intense grid groundwater slope and the surface watershed runoff totals, there is an indication that groundwater is not moving to the estuary at a significant flow rate. From a crude water budget, the precipitation of 162 cm is accounted for by 66 cm of runoff in the agriculture watershed and approximately 90 cm of pan evaporation. The sum of runoff (66) and evaporation (90) is 156 cm, which is only 6 cm less than the total precipation. It had been expected that the subsurface lateral movement of water would be a larger percentage of the water budget than the 6 cm implied in this calculation. The small lateral movement is somewhat substantiated by the intense grid values of water table slope. Using the July, 1979 contour lines (Figure 11), it can be calculated from slope, conduc- tivity, permeable depth and area, that the lateral flow in July accounts for about one centimeter of precipitation. It is hypothe- sized that some groundwater is reaching the drainage ditches and appearing at the flume to be measured as surface water. From this hypothesis it is suggested that subsurface groundwater movement as a pathway for pollutants to reach the estuary may not be as important as previously anticipated. The relatively deep drainage ditches appear to be the main mode of transport for nitrogen and phosphorus to the Bay ecosystem in this low flat coastal plain area. 46 DISCUSSION Surface Export A substantial number of diffuse source studies have now been completed on various land use types which can be used for comparison with the Horn Point watersheds. Table 14 reviews several studies where a variety of basins have.been investigated along with con- trasting types of development (e.g., suburban, shopping centers, urban). Kauppi (1979) found very high correlations of percent cultivation in a series of small basins with the amount of phos- phorus and nitrogen export in each. In totally forested basins 'he calculated .04 kg ha-Iyr-1 P and 1.3 kg ha -1 yr-1N export. In contrast, in basins under 70% cultivation, P was 0.34.kg ha-1yr-I 1 1 and N was 7.4 kg ha- yr- . Kauppi also concluded that drainage density and distance of fields from streams in the basin determined their relative influence on export. The greater the distance of fields from feeder streams, the less culitvation seemed to affect water quality. At Horn Point, our agricultural areas are immediately adjacent to the drainage ditches where flux measurements are made. This lack of buffering around the drainage ditches is one of the major reasons why the agricultural watershed at Horn Point has a higher value of P 0 kg ha- 1yr-I ) and N export (7.1 kg NO3+NO2 ha-1yr-1) than the average for the eleven watersheds at Rhode River studied by Correll et al. (1977). We estimate that unmeasured nitrogen fractions (NH 43 dissolved organic nitrogen) are approximately 50% of the NO 3+NO2 export at the TABLE 14. Dissolved export rates (kg ha- Iyr- from basins with varying degrees of development LAND USE AREA TOTAL TOTAL N:P REFERENCE PHOSPHORUS NITROGEN RATIO 70% cultiv. Loytaneenoja Basin, Finland .34 7.4 22 Kauppi, 1979 13% cultiv. Kuokkalanoja Basin, Finland .15 4.6 30 Kauppi, 1979 0% cultiv. Vaha-Askanjoki Basin, Finland .04 1.3 33 Kauppi, 1979 10c,38f,18o,17p,6r* N.Br. Muddy Cr. Rhode R., Md. 1.4 4.0 3 Correll et al., 1977 17c,31f,49o,2p,11r N.Br. Sellman Cr. Rhode R., Md. .6 2.4 4 Correll et al., 1977 28c,45f,5o,21p,lr S.Br. Sellman Cr. Rhode R., Md. 1.9 8.6 5 Correll et al., 1977 16c,46f,I2o,IOp,jIr Mean Rhode R. Watersleds, Md. .9 3.8 4 Correll et al., 1977 Single Fam. Suburb. Florida 0.2 1.5 8 Mattraw and Sherwood, 1977 Shopping Center 2.1 30.2 14 Hartigan et al., 1978 General Urban Gt. Lakes 0.3-2.1 6.2-10.0 5-20 PLUARG 1978 Developing Urban Gt. Lakes 23.0 63.0 3 PLUARG 1978 Presettlement forest Lake George, New York .04 1.2 30 Watson et al., 1979 Post settlement (96% forest) Lake George, New York .08 1.6 20 Watson et al., 1979 Presettlement forest Lake Wingra, Wisconsin .35 10.5 @30 Watson et al., 1979 Post settlement (75% urban) Lake Wingra, Wisconsin .61 10.6 17 Watson et al., 1979 *c=% crops; f=% forest; 0=% old fields; p=% pasture; r% residential 4@s 48 Horn Point agricultural watershed. Thus the total dissolved N export -1 -1 would be on the order of 10 kg ha yr This is also higher than any of the watersheds on the western shore studied by Correll et al. (1977) at Rhode River (see Table 14). This figure is in close agreement with the nitrogen exports reported on Lake Wingra and Lake George by Watson et al. (1979), but is lower than figures for most developed urban and suburban areas reported from similar flat terrain around the Great Lakes and Floria (Table 14). The dif- ferences between loadings reported at Rhode River and Horn Point watersheds can be partially attributed to the increased amount of land under cultivation in our agricultural watershed than reported by Correll et al. (1977). A detailed analysis of the inputs and outputs from the agricul- tural watershed is-presented in Table 15. Since soybeans comprised the largest crop cover, the input of nitrogen fertilizer was only 1.5 metric tons (M.T.), a small amount compared with what it would have been if corn was planted in a percentage more reflective of the equal mix of soybeans and corn normally planted in the Choptank basin. Although nitrogen fixation associated especially with the legumes (soybeans and clover) was in the range 3.5 - 7.8 M.T., most of this fixed nitrogen goes directly into organic matter and is not immediately available in the runoff. Therefore the nitrogen flux (0.9 M.T.) we report is lower than expected in years when corn is planted in the watershed. Present studies where corn is th6 only crop appear to confirm that the flumes had higher nitrogen concentra- tions (Fisher pers. com.). Another factor which may have diminished the potential export 49 of nitrate is the relatively wet spring of 1979. Alternating wet and dry conditions increase denitrification rates in agricultural fields (Ni elsen and Macdonald 191). In many areas of the eastern-shore, obvious nitrogen deficiencies were apparent on corn grown in the wetter fields in 1979. Therefore, because the high proportion of soybeans in the watershed in this year plus atmospheric losses, we suspect 10 kg ha-1yr-I N export to be a somewhat conservaive estimate for agricultural lands of the Choptank Basin. For compari- son in Delaware, Ritter et a]. (1979) found that Blackwater Cr. watershed (57% cropland) exported 20.6 kg N ha-1 yr- 1, while Stockley Branch (45%'cropland) exported 18.2 kg N ha- Iyr- 1, in 1976 and 1977. Also they report higher areas phosphorus (.58 kg ha-1 yr-I) from their watersheds during the same time period. Table 15 shows that twice as much phosphorus (3.0 M.T.) than nitrogen was applied to the agricultural watershed in 1979. However only a tenth of that moves in the soluble phosphorus fractions that we measured. We assume that a substantial amount of phosphorus moves with the particulate fraction. Table 16 shows that the forested watershed has a hundred times less phosphorus inputs -- all as precipitation and only a fourth of input is exported in the dissolved fraction of the runoff. The net difference may be taken up by the forest or exported in the particulate fraction. The nitrogen budget for the forested watershed (Table 16) is very unbalanced with a very small fraction of the nitrogen being exported. Our runoff rate is not quite as low as Bedient et al. (1978) reported (Table 17) but is much lower than Borman et al. (1977) found at Hubbard Brook (4.0 kg N ha yr The latter 50 TABLE 15. Mass balance calculation of inputs and outputs of nitrogen and phosphorus in the Horn Point agricultural watershed during 1979. ha. Parameter kqN/ha kgP/ha kgN kgP Fertilizers: INP 0 1 37 Soybeans (268 kg/ha 5-20-30) 13.4 53.6 496 1983 7 Corn (357 kg/ha 5-20-30)+ 17.9 71.4 125 500 (107 kg/ha Anhydrous Ammonia-82%N) 87.7 614 - 10 Red Clover (268 kg/ha 10-20-20) 26.8 53.6 268 536 1503 3019 N-Fixation: 37 Soybeansa 55-140 2035-5180 39 Corn and Otherb *4-3. 16-117 10 Red Cloverc 140-250 1400-2500 ---------- 3451-7797 86 Precipitationd 10.5 0.9 903 77. Estim. Inputs 6000-10000 3000 OUTPUTS Harvested Crops: 37 629 bu Soybeans (1.6kgN & .16 kgP bu) 27.2 2.72 1006 101 7 504 bu Corn (.41 kgN & .073 kgP bu) 29.5 5.26 207 37 10 30 T Clover (17.1 kgN & 1.4 kgP T) 153.9 4.2 1539 42 2752 180 54 Deni-trification (15% of applied N)e 225 - 86 Flume Export 10.0 0.9 860 81 Estim. Surface Outputs 4000 300 Net Difference 2000-6000 2700 Net Diff. per ha 23-70 31 allardy and Holsten 1976 bTiepkema and Van.Berkum 19,77 cStewart 1965 dMiklas et al. 1977 eAllison 1955 51 TABLE 16.' Mass balance calculation of inputs and outputs of nitrogen and phosphorus in the forested watershed at Horn Point during 1979. ha. kgN/ha kgP/ha kgN kgP INPUTS 35 N-Fixationa 1-17 -- 35-595 -- 35 Precipitationb 10.5 0.9 368 32 Estim. inputs 403-963 32 OUTPUTS 35 Denitrificationc ?. -- 0 35 Flume Export .16 .24 5.6 8.4 Estim. surface outputs 5.6 8.4 Net difference 397-957 23.6 Net diff. per ha 11.3-27.3 .67 aBorman et al. 1977 bMiklas et al. 1977 cViets 1978 TABLE 17. Nutrient export rates (kg ha- 1yr-1) assoicated with various crops and forested watersheds LAND Ortho P TSP TP N02t N03 NH3 TKN TN REFERENCE Contour Corn 0.16 1.65 1.62 .0.84 59.3 Alberts'et al., (1978) Terrace Corn 0.08 0.23 0.90 0.21 6.35 Alberts 6t al., (1978) Pine Forest 0.06-0.11 0.22-0.37 Duffy et al., (1978) Cultivated Duxbury and Muckland 0.06-30.7 39.2-87.5 1.0-1.9 Peverly(1978) Fallow 0.1-1.2 0.4-2.9 0.2-0.3 0.4-4.1 Nicholaichuk and Read(1978) Prairie 0.02. 0.03 0.11 0.12 0.14 0.71 Timmons and Holt(1978) Forest 0.21 0.06 Bedient et al., (1978) Cotton 1.11 6.7 11.6 Menzel et al., (1978) Wheat 0.3 2.2 7.2 Rangeland 0.04-0.06 0.54-1.86 1.7-6.3 Agric 1.0 7.1 This study Pine, .24 16 This study 53 investigators concluded that the 55 yr old Beech-Map.le Forest at Hubbard Brook is very conservative in terms of nitrogen retention. Therefore the pine forest at Horn Point and that studied by Bedient et al. (1978) have extremely "tight" nitrogen budgets. The reason that pine forests might have comparatively tight nitrogen cycling is that successional systems tend to be more efficient in trapping nutrients than systems nearer climax, where steady state (input=output) is approximated (Vitousek and Reiners 1975). Ground Water Concentrations The most remarkable aspect of the groundwater concentrations is the enormous increase,in nitrate in wells adjacent to the marsh. These concentrations (1.54 - 4.0 mg 1-1) are higher than the maximum reported by Stevenson et al. (1977) for the marsh embayment (1.1 mg 1-1) at Horn Point. It is not yet clear why this concentration occurs in this zone. Since there is no concurrent increase in chloride concentrations, there is little reason to suspect that this increased concentration is associated with brackish water ground- water intrusions from the estuary. Another possibility which seemed initially plausible was high nitrogen fixation rates in this area. However, a recent study of nitrogen fixation by Lipschultz (1978) in adjacent marsh areas where the high concentrations are present showed relatively insignificant N-fixation potential. A third hypothesis appears reasonable involving the loess cap which is deepest in zones surrounding the marsh. Boyce et al. (1976) have found up to 50-60 mg 1-1 nitrate in loess soils in Nebraska. The highest concentrations were found in low rainfall areas where 54 the nitrate remains unleached in the parent material. As rainfall increases the nitrate decreases to concentrations from l.Q - 5.0 mg 1- 1 -_ which are in the range we found. Boyce et al. (1976) speculate that the origin of the nitrate in the parent loess material might be due to nitrification of organic matter associated either with grassland during deposition or from the palesol. Biggs (pers. com.) doubts that this soil is really wind deposited since few radiocarbon dates are available. Further study of the nitrogen cycle of Mattapex soils is needed to promote our understanding of a soil type which has wide distribution around Chesapeake Bay. Perhaps the simplest explanation for the high nitrate concentra- tions is that they.are the result of the attempt at cultivation of essentially marsh muck. The highest NO2+NO3 value in Table 17 is associated wit'h cultivated muckland in New York. Duxbury and Peverly (1978) concluded that most of the nitrate associated with muck histosols is the result of mineralization of organic material and not directly from additions of fertilizers. Thus there is reason to believe that high nitrate concentrations found at Horn Point are also only indirectly related to cultivation and not directly to f erti I i zati on. Diffuse Source Loadings in the Choptank Basin In order to determine whether the N & P loadings measured at Horn Point watersheds reflected those that occur in other areas of. the CKoptank Basin, we compared our data to that simultaneously collected by the U.S. Geological Survey at Greensboro, Md. Since the Greensboro gaged station drains 293 square km of the upper basin it 55 can be used for testing whether the comparatively small scale watersheds at Horn Point reflect larger basin segments which have more complex land use patterns with more potential sources and sinks. Table 18 shows that the nitrogen export of the Upper Choptank River is in excellent agreement with our adjusted value for the agricultural watershed (10 kg N ha-1yr-1). Furthermore the phos- phorus export at Greensboro is only slightly higher than our agri cultural watershed. Therefore it appears that the land use mix in the predominantly agricultural watershed at Horn Point produces a very close approximation to the output of the larger upper basin. The results at Horn Point were then used to obtain the diffuse source loading of the Choptank River in Table 19. Of the four land use categories given in Table 1, marshes were omitted because of the continuing controversy whether they serve as net nutrient sources or sinks to the estuary (see Stevenson et al. 1977) and comprise less than 1% of the watershed. Although we did not study any developed lanq use categories, a range of values were chosen from studies of urban and suburban areas enumerated in Table 14. Since developed land comprises such a small proportion of the watershed (4%), only a small amount of error is expected with this approach. Total non- point loading was then estimated at 1.16 to 1.23 thousand metric tons (M.T.) of nitrogen and 160 to 180 M.T. of phosphorus. These values were then compared with those projected from most recent available data of point -source inputs to major segments of the- Choptank Basin (Table 20). Table 21 presents the final percentage diffuse source contribu- tion of N and P in each part of the Choptank River. For both 56 TABLE 18. Total nitrogen and phosphorus flux of upper Shoptank north of USGS Greensboro Gage (drainage area = 293 km ) for water year 1979a DISS. DISS. DISSOLVED DISSOLVED MONTH DISCHARGE CONC CONC TOTAL N TOTAL P MEAN CFS N P k g k,@ M 2d-' k9 knf d-' mg/1 mq/1 Oct 21 1.6 .07 0.32 .012 Nov 28 - - 0.32 .016 Dec 96 1.9 .11 1.5 088 Jan 417 1.6 .10 5.6 .348 Feb 646 - - 8.6 .917 Mar 371 1.,4 1.2 4.3 .185 Apr 183 1.2 .04 1.8 .061 May 135 1.9 .09 2.1 .101 Jun 241 1.7 .12 3.4 .241 July 85 1.5 .18 1.1 .123 Aug 77 1.1 .08 0.7 .052 Sep 83 1.2 .08 0.8 .055 2.75 0.183 Total export (kg N ha-lyr-1 10.04 0.67 all.S. Geological Survey (1979) M M Wd VMW M M AM M 404 ON 00 TABLE 19. Estimated nitrogen and phosphorus non-point (103 kg/yr)d loadings from various land use types in Choptank Basin TOTAL NON-POINT LOADING Segment Croplanda Forestb Developedc Low Est. High Est. NITROGEN: Lower Choptank 325.9 1.9 5.0 - 33.4 332.8 - 361.2 Upper Choptank 419.7 2.9 2.6 - 17.5 425.2 - 440.1 Tuckahoe Cr. 286.9 1.7 0.2 - 1.1 288.8 - 289.7 Delaware Segment 115.1 1.5 2.8 - 18.6 119.4 - 135.2 Basin Total 1147.6 8.0 10.6 - 70.6 1166.2 - 1226.2 PHOSPHORUS: Lower Choptank 42 * 8 2.8 .7 - 7.0 46.3 - 52.6 Upper Choptank 55.1 4.4 .3 - 3.7 59.8 - 63.2 Tuckahoe Cr. 37.7 2.6 .0 - .2 40.3 - 40.5 Delaware Segment 15.1 2.3 .4 - 3.9 17.8 - 21.3 Basin Total 150.7 12.1 1.4 - 14.8 164.2 - 177.6 aAssuming a loading of 9.9 kg N/ha and 1.3 kg P/ha bAssuming a loading of 0.16 kg N/ha and 0.24 kg P/ha cAssuming loadings of from 1.5 to 10.0 kg N/ha and from 0.2 - 21. kg P/ha (see Table 14) d I X 103 kg = 1 metri c ton = 2 205 1 bs. 58 TABLE 20. Estimated municipal discharge of nitrogen and phosphorus in the Choptank Basin in late 1970,sa Design Aver. flow N b P c Segment MGD MGD M.T./yr M.T./yr Lower Choptank R 10.582 7.026 291.3 97.0 (downstream from town of Choptank) Upper Choptank R .734 .673 27.9 9.3 (from town of Choptank to Delaware line) Tuckahoe Creek 0 0 0 0 11.316 7.699 319.2 106.3 a *Source: Solyst J and R Davidov. 1979.. The "208" Water Quality Management Plan for the Choptank Basin. Maryland Department of Natural Resources, Annapolis, MD. bAssumes a N loading = .03 9/liter wastewater Source: U.S. EPA Process Design Manual for Nitrogen Control C Assumes a P loading = .01 g/liter wastewater Source: U.S. EPA Process Design Manual for Phosphorus Removal (EPA 625/1-76-001a) 0 00 TABLE 21. Comparative nitrogen and phosphorus loadings associated with major Choptank River segments. a Diffuse So 9rce Estimated Percent Calculated nd MLW Volume Loading Total Loading Attributable to Concentratio Segment 106 M1 Metric Tons Metric Tons Diffuse Sources mg/L NITROGEN: Lower Choptank 1497 347.0 638.3 54% .42 Upper Choptank 68 432.6 460.5 94% 6.77 Tuckahoe Creek 8 289.3 289.3 100% 36.16 Delaware segment 2e 127.3 127.3+ 100% 63.65 Total Basin 1575 1196.2 4915.4 78% .95 PHOSPHORUS: Lower Choptank 1497 49.4 146.4 4910,10 .10 Upper Choptank 68 61.5 70.8 87% 1.04 Tuckahoe Creek 8 40.4 40.4 100% 5.05 Delaware segment 2e 19.6 _19.6+ 100%. 9.80 Total Basin 1575 170.9 277.2 62% 0.18 aCronin an d Pritchard 1975. bAverage non-point loading estimate from Table (19). CFrom Tables (19) and (20). dAssumes no losses due to: biological uptake, sedimentation or denitrification in the river or adjoining wetlands. eAssuming that drainage density is 1% of total land area of the segment (230 km') and with an average dep th of 1 meter. 60 nitrogen and phosphorus, non-point sources account for from approxi- mately 50% in the lower portion of the Choptank River t@) gsTentially 100% in the upper fresh water portions. The overall diffuse source loading percentage is 78% for N and 62% for P. One conclusion of our study is that diffuse source nutrient loadings are significant in the rural eastern shore tributaries of Chesapeake Bay with land use mixes and soil types similar to the Choptank River. Furthermore, our calculations suggest that nitrogen and phosphorus of point source inputs upstream in the Choptank-are minimal compared with diffuse sources. To improve water quality in the fresher portions of the Choptank River, efforts should be directed toward reducing outputs of N and P associated with present agricultural practices. However, significant reductions in algal blooms in the lower portions of the Choptank River could be obtained by improved treatment of sewage. Nitrogen removal appears much more critical than phosphorus, since it appears to be the limiting nutrient in late spring and summer in this area (Stevenson et al. 1977) when algal blooms are most prolific. Because advanced sewage treatment systems are presently very expensive, it might be more cost-effective to apply wastewater to forested land. Our study shows that the pine forest at Horn Point is very effective at retaining nitrogen inputs, and systems like this may be good prospects for spray irrigation. A study of spray irrigation has indicated that this disposal technique works well on a coastal plain site on the western shore at St. Charles, Maryland with only minor problems when the forest is oversprayed with sewage (Athanas et al. 1981). Species could be planted which have high 61 tolerance to waterlogging such as loblolly pine, white cedar or bald cypress. These species all have high commercial value and could be harvested periodically to help offset treatment costs. Finally Table 21 shows projected concentrations of N and P in the major segments of Choptank River. However, actual measured concentrations reported by Water Resources Administration (see Solyst and Davidov 1979) in the Choptank, during the late 1970's are about aL magnitude lower, with the same trend of increasing N and P in an upstream direction. This indicates that the river itself is assimilating N and P into organic material and "sinks out" a large proportion of the input loading. Also processes such as denitrifica- tion may be operating in it surrounding wetlands to liberate nitrate in gaseous forms. 62 FUTURE RESEARCH One problem which emerges from past research at Horn Point is the lack of accounting for the initial input of nitrogen and phosphorus in the mass balance calculation. It is obvious in Figures 12 and 13 that particulates could be a major term in the budgets of these watersheds. Although particulate N and P were not measured in this study, a subsequent year's data on sediment outputs is now being analyzed (Fi sher pers. com.). If particulate export of N and P do not turn out to be significant, the possibility of nutrient accumulation in the soils should be investi gated. Phosphorus is more likely than nitrogen to accumulate in the agricultural watershed. Both N and P are assimilated by the forest in proportion to 'its net productiv,ity which needs to be quantified for an understanding of its importance in the forested watershed. Also, effort should be made to determine the magnitude of organic and inorganic phosphorus.and nitrogen pools in both watersheds. More research is also needed to ascertain the relative loss of nitrogen attributable to denitrification and nitrogen fixation in both forested and agricultural watersheds. Rapid denitrification might occur when water tables are oscillating, accounting for a large percentage of the nitrogen imbalance seen in Fig. 12. In addition, the possibility that nitrates move into the estuary below the inter-flow zone intercepted by the ditches during periods of high rainfall, needs to be examined. This hypothesis could be tested by determining groundwater seepage into the bottom of Chesapeake Bay using techniques similar to those used by Lee NITROGEN k g h a/ y r 63 FERTILIZATION DENITRIFICATION N-FIXATION A 17.4 65.4 2.6 PRECIPITATION HARVEST 10. 5 AGRICULTURAL 32.0 10.0 ;;,- EXPORT WATERSHED Dissolved '- ? ,(thru flume) Particulate ? (IN) - (OUT) (EXCESS) GROUNDWATER 93.3 - 42-0 51.3 N-FIXATION FERTILIZATION DENITRIFICATION 0 9.0 ? PRECIPITATION 10.5 FORESTED 0.16 WATER8HED Dissolved >- EXPORT ? (thru flume) Particulate (IN) - (OUT)= (EXCESS) 19.5 - 0.2 = 19.3 GROUNDWATER Fi gure 12. Yearly nitrogen budget for agricultural and forest watersheds at Horn.Point PHOSPHORUS k g h a y r 64 FERTILIZATIOIN 35.1 PRECIPITATION HARVEST 0.9 AGRICULTURAL 0.9 WATE RSHED Bissolv EXPORT j ? "-(thru flume) p- -ar-t@i-c' u I a t e (IN) - (OUT) (EXCESS) 36.0 3.0 33.0 GROUNDWATER PRECIPITATION 0.9 FORESTED 0.24 Dissolved )I- EXPORT WATERSHED (thru flume) 2@. Particulate (IN) - (OUT) (EXCESS) )-9 GROUNDWATER 0.9 - 0.24 0.66 Figure 13. Yearly phosphorus budget for agricultural and forest watersheds at Horn Point 65 (1977) or Fellows and Brezonik (1979). The latter were able to measure subsurface hydraulic inputs into Lake Conway, Florida by using 1@simeters along the shoreline in the shallows and measured nutrient loadings simultaneously. Finally efforts should be made to evaluate the effects of alternative BMP's (e.g., buffer strips, using winter cover crops, grassed waterways, instituting "no-till" practices, and etc.) at reducing non-point loadings. Walter et a]. (1979) have cautioned that BMP's derived from previously developed soil and conservation practices have little direct effect on non-adsorbed or soluble pollutants (e.g., nitrate). More research is necessary to evaluate options to encourage removal of nitrates from runoff. A system of experimental watersheds equipped with flumes is needed to study effects of manipulating agricultural practices on reducing nitrate concentrations. In addition, it would serve as a more convincing longer term experiment to the local farm community, which now is skeptical of short term studies which are sometimes extrapolated beyond their limitati ons because of time necessities. A series of well designed long-term watershed studies would provide coastal resources managers with a unique and valuable data base.for guiding land use decisions in future years. 66 MANAGEMENT OPTIONS Previously the 208 plans mandated in Public Law 92-500, attempted to catalog and control pollution loadings when there was little understanding of the actual extent of the non-point source problems in various portions of Chesapeake Bay. For example, runoff from feedlots was thought to be a major diffuse source problem. However, overall budgets show these activities occur in such small proportions in this region that they are trivial compared with cropland loadings. Only after considerable amount of data is available, on surface and subsurface loadings and mass balance calculations made for each major watershed, can realistic control measures be formulated (Schmidt, 1979).. Coastal Zone Management could make a major impact in this area if it would promote the implementation of a groundwater/surface water quality monitoring system for major tributary segments of the Bay. This management option would have maximum impact by providing non-point source information essential for effectively carrying out provisions of the Clean Water Act. The State of Maryland Departmeht of Health and Mental Hygiene monitors core stations in Chesapeake Bay to determine concentrations over long time periods. To date, however, no scien- tific evaluation of what information is needed for ti.me-series statistics for trend analysis has been attempted. Other states, such as Illinois have already analyzed their monitoring network and found they could reduce by two-thirds the number of stations necessary for detecting trends (Wallin and Schaeffer 1979). The basic statistics for developing an evaluation of sampling freq.uencies monitoring 67 networks has been recently reviewed by Ward, et al. (1979). One management necessity that emerges from our study is the control of soils with very high nitrate concentrations. This area is adjacent to the mar5h areas and tends to be in the Mattapex series. Many Eastern Shore farmers cultivate very close to the marshes and Bay shorelines often disturbing the muck soil so that surface losses become probable. Efforts could be made to encourage or mandate wider buffer strips alongside the Bay and its marshes which would prevent this soil from moving into the estuary. We suggest that strong incentives such as easements are necessary to promote these green areas. Sharp and Bromley (1979) point out that one of the obstacles in reducing agricultural pollution is that although technology is currently available, cordination between governmental.agencies is the limiting factor in the implementation of a financial incentive program for enhancement of rural water quality. More research needs to be done to determine what type of vegetation should be encouraged in the buffer strips. A high nitrogen requiring non-leguminous crop which could be grown with no-till cultivation would be ideal. One possibility might be Reed Canary grass (Phalaris arundinacea), a leafy perennial of wide agricultural importance as a wetland grass. It can take up an average of 300 kg N ha-lyr-1 (Kardos and Sopper 1973). Precaution should be taken to exclude species which have any nitrogen fixation ass ociated with them, since that would only compound the high nitrogen concentrations in this zone. 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Inter., Fish and Wildlife Service, Biological Services Program (FWS/OBS-78166) National Technical Information Service, Springfield, VA. 335 p. Stewart, W.D.P. 1965. Nitrogen fixation in plants. Athalone Press, London. Strickland, J.D.H. and T:R. Parson. 1972. A practical handbook of seawater analysis. Fisheries Research Board of Canada, Ottawa. 310 p. Terry, R.E. and R.L. Tate 111. 1980. Denitrification as a pathway for nitrate removal from organic soils. Soil Sci. 129:162-166. Timmons, D.R. and R.F. Holt. 1978. Nutrient losses in surface runoff from a native prairie. J. Environ. Qual. 6:369-373. Tjepkema, J.D. and P. Van Berkum. 1977. Acetylene reduction by soil cores of maize and sorghum in Brazil. Appl. Environ. Microbiol. 33:626-629. Viets, F.G. 1978. Mass balance and flux of nitrogen as aids in control and prevention of water pollution. p. 173-182. In D.R. Nielson and J.G. MacDonald (eds.), Nitrogen in the envi-ronment. Academic, N.Y. Vitousek, P.M. and W.A. Reiners. 1975. Ecosystem succession and nutrient retention: a hypothesis. Bioscience 25:376-381. Wallace, McHarg, Roberts and Todd. 1972. Maryland Chesapeake Bay Study. A report to the Maryland Department of State Planning Committee. 403 p. Wallin, T.R. and D.J. Schaeffer. 1979. Illinois redesigns its ambient water quality monitoring network. Environ. Manage. 3:313-319. Walter, M.F., T.S. Steenhuis and D. Haitch. 1979. Nonpoint source pollution control by soil and water conservation practices. Trans. Agric. Soc. Agric. Engin. 22:834-840. Ward, R.C., J.C. Loftis, K.S. Nielsen and R.D. Anderson. 1979. Statistical evaluation of sampling frequencies in monitoring networks. J. Water Pollut. Control Fed. 51:2292-2300. Watson, V.J., O.L. Loucks, J. Mitchell and N.L. Clesceri. 1979. Impact of development on watershed hydrologic and nutrient budgets. J. Water Pollut. Control Fed. 51:2876-2885. I I I APPENDIX A I I I I I .. I 0 1 I I a I I I I I I I Al One Day Record of Storm Hydrograph for Parshall Flume at Agricultural Watershed, HPEL February 25,.1979 $10kM OF 25 1979 TIME OF IST PLADING. @J: do UPSTRM DWNSTR SUBMRG CO 110 CN FREFLO ACTUAL I1EAD HEAD NA710 FACTOR DISCH DISCH TIME HA KH H A / HB Q C 10 F 0 F QC OT D a 07 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - (FT) (FT) (CFS) (CFS) (MIN) (CU.FT) (IN) ------------------------------ ----------------------------------------------- U 3.44 3.3o :983 .511 03.06 42.47 30.0 76440.2 .0000 3u 3.34 3.?Y .985 SC3 79.33 39.87 .0989 oU 3'. 28 3.23 .985 SC4 77.11 30.82 30.0 71760.3 .1917 VU 3.25 3.18 .970 .525 76.no 39.94 30.0 69884.1 .2821 110 3.17 3.11 .981 .516 73.10 37.74 30.0 7im.4 .3750 15U 3.09 3.03 .981 .518 7n.23 3 3 8 30.0 67935.8 .46?9 3o.0 65485.6 lbu 3.00 2.95 .955 .508 67.05 34.09 30.0 61367.5 .5476 d1U e.91 Z.btj .963 .510 63.93 32.62 30.0 58715.4 .6270 24U 1.0 2.79 .986 SCO 61.20 30.59 30.0 -55038.5 .7029 Z70 2.76 2.72 .986 .501 58-04 29.47 .7741 30.0 53053.6 300 2 . 70 2.66 .985 .502 56.85 ?b.54 30.0 51373.2 .8427 1.5 U 2.66 2.62 .985 SC3 55-54 2?.92 .9091 30.0 50263.6 360 2.60 2.57 .98b .491 53.59 26.21 .9741 3vu 1.55 2.53 .992 .4 78 51-9b 24.84 30.0 47324.6 1.0354 30.0 44703.5 44U 2.50 2.48 .99k .478 50-40 ?4.1c 1.0932 30.0 43387.9 45U 4.45 2.44 .996 .465 48.83 22.69 1.1493 4bU 2.41 2.41 1.000 .450 47.58 21.43 30.0 40837.8 1.2021 30.0 3b531.5 51u 2.39 2.3b .996 .465 46.97 21.84 1.2520 30.0 39312.t@ 54U 2.36 2.35 .996 .465 46.05 21.42 1.3028 30.0 3057.9 57U ?.34 2.32 .991 .4dO 45.44 21.82 1.352? 30.0 39274.4 6UU 2.31 ?.30 .994 .466 44.53 [email protected] 1.4035 6JU 2.26 2.24 .991 .481 43.03 20.71 30.0 37311.b 1.4518 66U 2.22 2.21 .995 .466 41.84 19.50 30.0 37273.6 1.5000 30.0 35106.4 6vo 2.18 2.16 1.000 .450 40.67 16.32 1.5454 140 2.16 2.14 .991 .4a3 40.08 19.35 30-0 32973.0 1.5880 30.0 34826.1 75U 2.16 2.15 .995 .467 40.08 18.70 1.6331 30.0 33663.3 Ido 2.19 Z.17 .991 .4b? 4n.96 19.75 30.0 35554.0 1.6766 slu 1.22 ?.23 1.005 .000 41.?14 too 1.7226 30.0 .0 040 2.29 2 . 2 is .996 .466 43.93 20.45 1.7226 30.0 36817.5 87U @.17 2.15 .991 .483 4n.37 19.48 30.0 35068.1 1.7702 YUU 2.18 2.16 .991 .482 40.67 19.62 1.8156 YSU 2.19 2.16 .986 .498 40.96 20.40 30.0 35310.8 1.8612 30.0 36725.9 v&U 2.20 2.17 .986 .4 96 41:25 20 54 30.0 36972.8 1.9087 9yu Z.20 2.16 .982 .514 41 25 21:19 30.0 36147.8 1.9566 IUZO 2.19 2.15 .982 .514 4n.96 21.05 30.0 37897.9 2.0059 1U5U 2.25 2.?6 1.004 .000 42.73 .00 2.0549 30.0 .0 1Oa0 2.43 2.33 .959 .594 40.20 28.62 30.0 51513.3 2.C1549 MU Z.53 2.41 .953. .616 51.35 31.61 30.0 .56892.2 2.1215 1140 2.54 2.4b .976 .533 51.66 27.52 30.0 4.9537.3 2.1951 111U 2.52 2.45 .972 .547 51.03 27.92 30.0 50256.5 2.2592 IdUO 2 .'49 2.44 .980 .520 50.08 26.06 30.0 46907.2 2.3242 123U e.46 2.40 . 97c) .535 49.14 26.31 30.0 47332 .2 2.384a lktlu 2.41 2.34 .971 .@52 47.58 26.25 2.4461 12VU 2.40 2.33 .971 .55Z 47.27 26.09 30.0 47241.7 2.5072 30.0 46970.9 1320 2.39 2.31 .967 .567 46.97 Z6.63 2.5679 135u @.39 2.31 .967 .567 46.97 26.63 30.0 47932.0 2.6299 13tO 2.35 2.27 .96t .569 45.74 26.02 30.0 47932.0 2.6919 141U Z.45 2.35 .959 .593 .F.. 8 5 28.93 30.0 46844.9 2.7525 --------- ------------------------------------------------------------------- 10 C OhVt R 7 j -Y (HE S ru C U . F T , P'U L I I I'L Y UY . 7 7 32. ot, A2 One Day Record of Storm Hydrograph for Parshall Flume at Agricultural Watershed, HPEL February 26, 1979 SYUNM Of z 26 1979 TIMF Of IST PtAVIN6: U:00 UPSTRA DWNSTA SuS.46 CoRRC,@ FREFLO ACTUAL HEA D HLAD pATI 0 FAC T0 , DISCH 0 1 S C H TImE HA HH A/"b 0 C / a F OF cc DT Do OT ---- ---- ----- ----- ----- --- (FT) (FT) CCFS) (CFS) (MIN) (CU !T) ---- N - - - - - - - - - - - - - - - 2- -. Z 3 . . - -- - 'j 6 2 30.0 51513.8 .00;0 3U Z.41 .30 .951. .0 Gi, 47.58 2ti . 9 9 30.0 52190.3 .0666 0 11 z . 7 1 2.51 .926 .705 57.18 40-28 30.0 72512.9 .1341 YU 2 . 7 @' 2.56 .921 .721 59.51 42.88 30.0 77181 .3 .2279 12U 2. ?6 z.56 .9zb .7CO $8.84 41 .2 1 30.0 74181 .2 .3277 150 2.65 2.46 .9?b .698 55.21 36- 54 30.0 69366.0 .4237 lau 2.50 2.36 .922 .718 52.30 37.53 30.0 67552.7 .5134 ZIU 2.4e 2 . L, Y .923 .713 49.77 35.49 30.0 63873.4 .6008 240 Z.39 2.23 .933 .6a3 46.97 32.07 3o.o 57721.1 .6834 270 2.30 2.17 .943 .647 44.23 2b.62 30.0 515ZZ-9 .758D JUU 2.23 2.10 .942 .653 42.14 27.53 30.0 49556.8 .8247 33U 'e: 14 ?.UI .931 .691 40.08 27.69 30.0 1-9845-5 .8987 Jou 2 IV 2 .1 ti .995 .466 40.96 19.10 30.0 34382.1 .9532 3qu 2.1t 2.05 .949 .628 40.08 25.16 30-0 45291.2 .9977 4,c U 2 . b4 1.96 .961 .587 36.65 21.51 30.0 30 23 - 8 1.0563 450 . 1 . 14 1.92 .965 .573 35.25 20.20 1.1063 30.0 36355-3 4au 1.94 1.88 .969 .558 33.88 18.91 1 .1534 51U 1.90 1t4 .96t .560 32.79 18.37 30.o 34033.2 1 1974 30.0 33074.5 540 I.b6 1- b 0 .96b .563 31.72 17.85 30.0 32125.5 1.2402 57U I.b3 1.75 .956 .603 30.92 18.63 30.0 33537.4 1.2817 6UO 1.83 1.?y .97b .527 30.92 16.2e 30.0 29302.9 1.3251 6JU 1.79 1.73 .966 .567 29.87 16.94 30.0 30488.4 1.3630 6C. U 1.81 1.70 139 .662 30.34 20.12 30.0 3621?.b 1.4024 ovo 2.09 1.68 .804 .912 38.07 34.73 30.0 62519.7 1.4492 '74eu 1.92 1.93 1.005 .000 33.33 .00 1.5301 30.0 .0 7bu 1.78 1o73 .972 548 29.60 16.23 30.0 ?9214.8 1.5301 hi U 1.73 1.67 .965 .571 28.31 16.17 30.0 29109.4 1.5679 bio 1.70 1.65 .971 .553 27.55 15.23 30.0 27413.0 1.6055 64U 1.69 1.63 .964 .5 74 27.29 15.67 1.6410 30.0 28202.6 70 1.65 .971 .553 27.55 15.23 1.6775 30.0 27413.0 VaQu 1.73 1. f, 8 .971 .551 28.31 15.60 30.0 28OS3.9 1.7129 v3u 1.76 1.11 .971 .549 29.09 15.98 30.0 28760.6 1.7492 960 1.76 1.?3 .983 .510 29.09 14.83 30.0 20689.6 ioa64 Yqu 1.73 1.71 .98b .491 28.31 13.89 1.8210 luio 1.('6 1.6d 1.012 .000 26.54 .00 30.0 25007.5 1.8533 iv@u 1.59 1.61 1.013 OUO 24-61 OU 30.0 .0 1.8533 Jobo 1.50 1.52 1.013 . .000 22.64 .00 30.0 0 1.8533 1110 1.44 1.45 1.007 .000 21.24 U0 30.0 .0 1.8533 114U 1.3? 1.3b 1.007 XCO 19.65 :Clo 30.0 .0 1.8533 1170 1.30 1-30 1.000 .450 18.10 8.15 30.0 .0 1.8533 leuu 1.24 1.25 1.00b .000 16.81 .00 30.0 14674.0 1.8723 1M I-IM 1.20 1.017 OGO 15.55 .00 30.0 .0 1.8723 Ilt,U 1.12 1.23 1.09b .0G'0 14.33 .00 30.0 .0 1.8723 30.0 .0 IZYU 1.06 1.06 1.000 .450 13.15 5.92 30.0 10659.4 1.8723 132U 1.01 1.02 1.010 .000 12.19 .00 30.0 .0 1.6861 1350 Y 7 .95 9 79 .522 11-44 5.97 '30.0 107S4.6 1.8861 3CU 4" .525 1 rj. 71 5.63 1.9000 1 .91 7 t lo.0 10127.8 141U 7 1 .5 e 14 19-00 5.29 1.9131 ------------ ------------------------------------------------------------------ 0 *,v i R 7 1 N L P4 E 5 TO F I - - 0 L T I Y .771"- CY) a 2 Go a s 2-0000*01+ O.OOUO +----------- ----------- ----------- ----------- 0. 200. 1.00. 600. 600. 1000. 1200. 1400. 1600. TIME *AINS* Figure Aa Calculated hydrograph for agricultural watershed at HPEL, February 25, 1979. 4-UOU0401. Q D I 3.0oo0ioli S A G E C I DOUD 40 1 9 Q Q 0.0000 - - - - - - - - - - - - - - - - - - - - - - - - - - - - 4----------- 4 - - - - - - - - - - - - - - - - - 0. 200. 4.00. 600. $00. i0ob. 1200. 1400. 1600. TIME AMINS* Figure Ab Calculated hydrograph for agricultural watershed at HPEL, February 26, 1979. I I I I v I APPENDIX B I I - -1 I I i I . . I I I I I I I I I i I Bl TABLE WELL NO. A- 2 SAMPLEI vg NIL jig NIL jig NIL lig PIL vg P/I OATE NITRATES NITRJTES AMMONIA ORTHO TOTAL mg Cl/t PHOSPHATE PHOSPHATE CHLORIDE! 08-17-78 1 15 20 08-23-78 2 9 18 28-31-78 5 50 29-07-78 5 18 09-14-78 5 09-21-78 2,600 4 0,5 30 46 09-27-78 3 200 0 5 30 q9 10-12-78 3,200 5 0 is's 44 10-26-78 3.200 5 10 9 39 11-09-78 1,900 0. 9 10 48 11-23-78_ 2,300 1 0 a 40 12-07-78 1,800 1 0 20 47 12-21-78- -- 2,200 1 5 14 36 01-04-79 - 0 0 50 45 01-18-79 3.400 1 20 0 90 47 09-01-79 3.000 2 80 5 40 42 02-15-79 4,600. 2 320 0 24 48 03-01-79 4,600 1 130 0 20 1 48 03-15-79_ 5,200 3 - 0 34 58 03-29-79 5.800 5 30 0 32 so 04-11-79 6.400 2 26 9 26 49 04-26-79 6.600 2 270 0 so 49 OS-10-79 6.200 3 38 7 40 48 05-24-79 11.000 2 83 8 24 49 8 142 17 94 204 4,292 6 -- 16 -30 44 07-06-79 2,364 7 63 20 22 07-19-79 2,740 7 36 7 28 36 08-09-79 3,109 is 470 36 86 39 08-23-79 3.770 8 87 a 68 38 B2 TABLE WELL NO. A-11 SAMPLE vg NIL V9 NIL pq NIL )jq P/1 lig PIL DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg CI/l PHOSPHATE PHOSPHATE CHLORIDES 08-17-78 40 20 08-23-78 100 110 08-31-7u 15 18 09-07-78 9,9 10.10 09-21 8 -78 0 3U 64 09-27-78 3 0 5 66 10-12-7u 340 0 5 12-07-78 7bO 2 0 18 54 12-21-78 410 1 9 24 01-04-79 0 jo 51 01-18-79 Z40 9 11,380 0 90 b6 02-01-79 240 2 6UO 5 12 02-15-79 Z20 3 11.300 3 22 b2 03-01-79 38o 4 640 0 12 50 03-15-79 080 3 - 0 0 47 03-29-79 660 3 80 51, 50 20.0 2 04-11-79 580 5 1 166 32 68 6 04-26-79 440 5 581 190 274 1 6 -05--10-'79 60 1 2.19B- 165 246 20 05-24-79 72 4 > 2450 - 140 34 06-07-79 253 58 1414 6 58 50 06-21-79 638 12 7 24 49 07-06-79 842 11 1587 4 17 54 07-19 -79 270 4 1717 out 28 out 08-09-79 2.201 21 1.090 0 8 82 08-23-79 3,232 50 790 1 49 80 B3 TABLE WELL NO. A- 27 SAMPLE jig Ng tig N/l ijg N/,t ug P/1 tig PIL DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg Cl/l PHOSPHATE PHOSPHATE CHLORIDE! 08-17-78 4 30 80 08-23-78 3 9 100 08-31-78 18 5 18 09-07-78 58 5 10 09-14-78 20 0 - 09- 21- 78 60,66.82 4 0.0 30 el 09-27-78 34 1 8 5 9 90 10-12-78 10 u 0 0 )Do 10-26-78 14 1 - 9 82 11-09-78. 12 5 6 a 90 11-23-78 20 2 0 0 84- 12-07-78 30 1 0 20 loo 12-21-78 22 5 0 u 90 01-04-79 115 5 0 40 loo 01-18-79 - - 900 0 64 97 02-01-79 16 10 640 0 12 45 02-15-79 28 10 1620 1 '28 98 03-01-79 28 16 590 0 14 1 98 03-15-79 46 a - 0 0 89 03-29-79 53 10 350 0 60 100 04-11-79 100 11 322 0 40 97 04-26-79 84 10 050 12 26 107 05-16i-79 92 10 -252 0 Z? 78 05-24-79 110 9 45S 11 40 98 06-07-79 137 9 403 6 9 240 48 24 07-06-79 61 4 352 0 0 Be 07-19-79 27 6 1,290 0 48 108 08-09-79 42 a 1,349 2 38 92 08-23-79 18,22 4 752 1 123 95 B4 TABLE WELL NO. M- SAMPLE lig NIL V9 NIX jig NIL lig PIL jig P/I DATE NITRATES NITRITES AW40NIA ORTHO TOTAL mg Cl/L PHOSPHATE PHOSPHATE CHLORIDES m-17-78 0 30 130 08-23 2 185 300 8-31-78 20 5!) 70 9-07-78 10 35 70 09- 1 -78 12 9 20 09-21-78 520 21 0 30 28 10-12-18 1 15 12-07-78 920 0 u ISO 13 12-21-78 800 0 11 16 11 01-04-79 680 6 is 60 14 01-18-79 610 3 420 20 15 02-01-/9 800 0 300 5 64 12 02-15-79 1,040 1 470 4 24 14 03-01-79 1.000 1 110 -5 22 14 03-15-79 1,020 1 0 0 12 03-29-79 1,000 1 50 9 6 18 04-11-79 1.250 3 178 9 44 22 04-26-79 1.150 1 58 45 80 36 05-11-79 1,080 a 20' 15 50 10 05-24-79 960 4 42 17 42 26 06-07-79 960 8 96 13 64 47 06-21-79 876 20 21 36 8 07-06-79 585 1 17 0 0 10 07-19-79 806 1 17 contax. 28 11 08-09-79 1.0.81 4 192 6 1 48 11 08/23/79 920 3 61 6 103 10 00 '0 r6 17 17 B5 TABLE WELL NO. M-34 SAMPLE jig NIL 9 jig NIL jig OAT NITRATES NJ ITES AMMONIA OR P P/- T:/f THOL 'TOTAL' mg C11L PHOSPHATE IPHOSPHATE CHLORIDES 08-17-7B 0 45 120 08-23-78 74 1 15 0 OB-31-M 210 12 0 09-07-78 152 12 18 .09-14-78 110 0 - 21-78 -11Z,126 5 0 0 24 10-12-78 46 0 5 35 3 12-07-78 70 0 7 18 24 12-21-78 23 2 5 14 20 01-04-79 60 3 0 30 23 01-18-79 20 10 1300 5 90 24 02-01-79 20- L 2 680 5 76 21 22 02@15-79 50 4 765 5 22 03-01-79 34 6 660 2 34 23 03-15-79 44 3 0 0 20 03-29-79 67 4 305 0 52 22 04-11-79 58 2 298 5 32 22 D4-26-79 2 05-04-79 69 4 13 52 20 05-10-79 74 3 360 6 32 20 05-24-79 82 4 770 17 48 24 06-07-79 106 2 662 11 70 31 06-21-79 108 0 12 39 20 07-06-79 86 4 1306 o 30 18 07-19-79 77 3 1400 1 33 19 08/09/74 85 6 1098 14 94' 22 08/2 50 3 838 11 168 20 6 18/A/7, B6 TABLE WELL NO. W- 1L I SAMPLE Sig NIL lig NIL jig NIL lig PA jig P/1 DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg CIA PHOSPHATE PHOSPHATE CHLORIDES 08-17-78 8_4 1 9 30 08-23-78 56 3 0 24 09-21-76 31 60 1 1 10-12-70 92 9 0 01-18-79 240 T.T. 24 T.T. T.T. 02-01-79 120 6.6 - 20 60 48 02-15-79 280 3 >10,000 30 70 86 03-01-79 160 4 3,500 a 6 125 03-15-79 44 z a 0 188 03-29-79 48 7 -1-65 0- 0 220 05-11-79 72 22 938 a 14 245 05-24-79 60 3 980 7 10 255 06-07-79 130 14 1.539 5 10 175 06-21-79 --- I T. Turbid 25 07-06-79 250 6 655 0 11 82 07-19-79 37 2 695 out -11 out 08-08-79 194 8 348 6 29 78 08-23-79 146 19 286 2 17 56 B7 TABLE WELL NO. m- 5z SAMPLE jig N/I pq N11 jig N/L lig P/,t lig PIL DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg Cl/L PHOSPHATE PHOSPHATE CHLORIOES 08-17-78 60 90 08-23-76 50 60 08-31-78 30 50 09-07-78 25 10 09-14-78 40 - 09-21-7ti 6 20 30 28 10-12-78 -700 0 0 15 18 12-07-78 900 0 12 40 27 12-21-78 1,000 0 25 22 24 01-04-79 1.400 6 5 30 27 01-18-79 1,000 0 140 7 90 25 02-01-79 1,9DO 0 1200 6 20 22 02-15-79 2.000 2 350 is 28 24 03-01-79 2,100 0 120 7 22 23 03-15-79 2,700 0 0 0 22 03-29-79 2,300 1 12 8 32- 24 04,-11-79 2.300 3 42 9 44 22 04-26-79 2,000 1 104 6 44 21 06-10-79 2.100 1 18 22 .90 20 05-24-79 2.050 3 48 12 32 22 06-07-79 1,750 2 15 8 60 32 06-21-79 1,125 0 16 24 38 07-06-79 1,358 2 21 0' 0 20 07-19-79 1,400 3 275 8 16 18 08-09-79 1.146 7 122 34 65 20 08/23/79 741 1 20 66 20 B8 TABLE WELL NO. SAMPLE jig N/1 jig N11 lig N/l jig P/t ljg P" DATE NITRATES NITRITES AMMON I A ORTHO TOTAL mg Cl/L PHOSPHATE PHOSPHATE I'CHLORIDES 0A.17-7A 5 35 210 la-_w- .8 1 90 75 120 OY-01-7H 224 85 80 09-11-7fl 0 09-il-76 132,11600 70 10-12-78 - 600 47.44 12 40 450 12-07-78 127 6 300 400 3bO 01-04-79 13 03-01-79 152 4 1420 0 475 03-15-79 58 5 0 Interf. 490 03-29-79 38 13 330 5 104 490 05-04-79 43 1 0 INTER.PRECII- 450 480 05-10-79 450 2 131 0 INTER PRECIP. 505 05-24-79 78 5 160 12 Interf. 535 06-07-79 106 3 119 Greei 11 Interf. 1895 06-21-79 44 3 11 Interf. 442 07-06-79 221 3 161 Greei 2 Interf. 392 07-19-79 2 132 2 51 455 326 08-09-79 368 3 136 20 86 335 08-23-79 40B 5 276 21 129 316 41 326 L 38 f4OB B9 TABLE WELL NO. W- 32 SAMPLE lig N/l pg NIX jig NIL vig pht V9 PIL DATE NITRATES NITRITES AMMONIA ORTHO TOTAL nv Cl/l PHOSPHATE .-PHOSPHATE CHLORIDES 0 -17-78 70 130 08-23-78 85 120 iio 160 09-07-78 40 80 09-21-78 9 20 60 26 10-'12-78 340 2 9 20 25 12-07-78 480 32 65 96 335 -01-04-79 184 7 10 50 135 01-18-79 133 1 -270 30 86 255 02-01-79 20 0 560 25 64 360 02-15-79 58 1 640 8 30 390 03-01-79 67 1 590 5 26 405 03-15-79 60 1 0 0 390 03-29-79 52 50 8 42 165 05-11-79 64 0 66 13 50 465 Qq_24-7Q 72 S 12 400 06-07-79 91 6 55 17 -88 1150 06-21-79 100 1 11 29 340 07-06-79 75 1 53 0 39 350 07-19-79 76 1 54 12 25 360 08-09-79 68 2 110 70 360 08-23-79 94 5 -49 13 95 360 B10 TABLE WELL NO. W. g3_ SAMPLE tig N/I jig N/I jig N/R. jig P/I jig P/I DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg CI/l PHOSPHATE IPHOSPHATE- CHLORIDES 08-17-7R 2 60 8U 01-04-79 13 18b 340 14 01-18-79 490 21 1790 - 420 29 U2-UI-lg 360 0 680 25 40 34 3-91-79 440 4 500 13 50 42 03-15-79 280 0 20 52 47 03-29-79 310 11 190 25 60 56 05-11-79 460 43 >360 145 220 58 05-24-79 400 3 805 84 132 80 06-07-79 610 13 826 117 204 55 06-21-79 2 45 so 59 07-06-79 103 2 250 0 37 66 07-19-79 out W.E.S 585 -- -- 57 DB-09-79 123 3 957 0 yellow 55 08-23-79 154 3 113 92 157 43 Bll TABLE WELL NO. W- 135 SAMPLE jig N/I jig N/1 lig N/L lig P/t jig P/1 DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg CIIL PHOSPHATE PHOSPHATE CHLORIDE! 08-17-78 56 10 0 60 08-23-78 100 5 0 10 08-31-78 96 0 e4 09-01-78 64 u 0 09-14-78 70 20 09-21-7a 61.62 5 0 0 84 09-27-78 80,58 0 5 82 10-12-78 10 0 0 0 98 10-26-78 51 0 0 5 100 11-09-78 46 0 5 0 102 fl-Z3-78 80 1 0 0 100 12-07-78 85 8 5 10 118 12-?1-78 70.75 5 5 6 110 01-04-79 - 4 6 44 59 01-18-79 300 10 1700 -- .70 51 02-01-79 200 2 620 0 20 42 OZ-15-79 34U 3 4100 4 24 42 OJ-01-79 340 7 1500 u 18 bo 03-l!)-79 290 1 0 0 52 03-29-79 273 4 72 8 32 56 04-11-79 247 2 173 0 20 57 04-26-79 ;53 3 102 0 30 56 05-10-79 18 4 300 0 16 185 05-24-79 19 6 386 8 6 185 06-07-79 39 0 320 0 6 120 06-21-79 25 11 7 15 104 07-06-79 is 1 524 0 0 102 1 56 0 19 90 U8-09-79 43 4 957 0 100 102 08-23-79 ill 8 680 4 100 73 B12 TABLE WELL NO. W- 141 SAMPLE Vg N/l jig N/I vg N/L lig PA pg P/1 DAT E N I I RAT ES NITRITES AMMONIA ORTHO TOTAL mg CIA PHOSPHATE PHOSPHATE CHLORIDES 08-17-78 0 08-23-78 0 -08-31-78 136 9 18 ug-07-78 30 5 70 1 09-14-78 50 5 0 Oq-,2i-78 50,44.84 0 0 17 09-27-78 T.T. 25 12 18 10-1?-78 38 2 0 9 32 10-26-78 --60 0 9 16 11-09-78 10 0 5 10 19 11-23-78 fl 2 0 8 15 12-07-78 19 0 0 14 18 12-21-78 14 1 5 0 16 01-04-79 28 0 0 46 1 19 01-18-79 12 2 280 0 70 19 02-01-79 8 0 280 0 20 15 02-15-79 28 1 640 3 16 16 03-15-79 10 2 0 0 1 lb 03-29-79 55 1 145 9 44 17 04-11-79 40 3 352 8 26 16 04-26-79 32 2 7350 7 32 15 05-11-79 _16 2 7350 6 30 14 05-24:79 4 441 17 -60 16 06-07-79 42 0 565 0 44 14 06-21-79 37 0 - 5 24 .9 1 396 4 15 15 07-19-79 29 1 367 3 28 -14 08-09-79 44 1 393 0 97 14 08-23-79 2 570 5 85 16 B13 TABLE WELL NO. W- 143 SAMPLE jig NIX lig NIXES vg NIX P/1 DATE NITRATES NITRIT AMMONIA 01J&THIL ITJ90TAL .9 CIIL PHOSPHATE PHOSPHATE CHLORIDES 12 nA-21-7A -5 10 nA.11-2g 5 18 nq-nZ-_7A_ 6 5 0 ng-14-7g 20 5 ng-23 -za_ -lAaU-U- 0 0 32 04-27--70- V? -- 4 .5 15 34 10-12-7B 100 0 0 0 10-2 -78 64.71 0 0 9 30 11-09-78 58 0 15 0 36 11-23-78 42 0 0 0 32 12-07-78 52 0 0 16 31 12-21-7-8 --80 - 1 0 0 34 01-04-79 51,68 0 0 32 38 01-18-79 ----- ------ 140 -------------- 37 02-01-79 52 0 95 0 12 36 02-15-7.9 92 2 240 5 16 36 03-01-79 84 2 240 0 12 36 03-15-12____@ 60 0 -0 0 36 03-29-79 90 8 207 0 24 36 04-11-79 82 7 3 6 42 35 04-26-79 80 4 126 0 34 34 44 2 7350 13 54 16 05-24-79 50 10 315 17 44 36 06-07- 79 101 0 171, 10 66 36 06- 21- 72--- 126 14 11 35 34 7= a L- 7 9 ----j 5j 7- low 0 14 33 07-19-79 IH8 0 IDW 32 08-09-79 164 26 1 62* 34 -08-23-79-- --233 5 22 4 107 34 B14 TABLE WELL NO. W- 144 SAMPLE vg N/l jig N/l jig N/k lig PA lig PA DATE NITRATES NITRITES AMMONIA ORTHO TOTAL mg CI/I PHOSPHATE PHOSPHATE CHLORIDES 08-17-78 72 9 20 08-31-78 108 9 24 09-07-78 --70 12 24 09-14-78 18 9 0 09-21-78 64,50 10,0 40 30 09-27-78 SZ,66 1 9 5 42 10-1-2-78 23 3 0 0 14 10-26-78 44,36 0 0 5 28 11-09-78 84 1 0 0 32 11-23-78 17 2 0 0 26 12-07-78 15 1 0 14 @8 IZ-21-78 12 1 5 0 Z9 01-04-79 1 1 9 36 90 30 01-18-79 19 3 280 5 70 31 02-01-79 4 0 500 0 76 36 02-15-79 30 2 350 3 18 28 03-01-79 34 1 640 2 20 28 03-15-79 30 27 - 0 0 Z8 03-29-79 40 2 212 0 32 28 05-11-79 34 2 236 10 32 25 05-24-79 34 7 207 16 22 28 06-07-79 43 0 251 0 50 36 06-21-79 45 0 10 30 27 07-06-79 38 1 318 5 13 27 07-19-79 11 0 282 5 31 26 08-09-791 40 2 213 3 114 26 L 08-23-7 42 4 231 10 167 22 B15 TABLE WELL NO. W- 163 SAMPLE1 pq N/A vig N/l jig Nlk pg P/1 jig P/A DATEJ NITRATES NITRITES AMMONIA ORTHO TOTAL mg Cl/l PHOSPHATE PHOSPHATE CHLORIDES 08-17-78 48 0 40 40 08-23-78 52 6 20 30 08-31-78 24 9 24 09-07-78 8 9 0 09-14-78 24 @20 0941-78 32.18 -4_ 16 30.50 09-27-78 20 1 12-07-78 10 12-21-78 9 3 0 0 12 Ul-04-79 16 13 5 32 30 01-18-79 20 43 1390 0 50 60@ 02-01-79 18 860 3 20 59 02-15-79 36 21 900 4 22 58 03-01-79 20 20 900 10 60 03-15-79 14 6 0 0 58 03-29-79 25 16 180 0 20 58 04-11-79 16 -18 206 0 48 60 04-26-79 21 12 92 0 28 60 05-10-79 0 21 21 212 0 50 60 05-24-79 24 16 235 22 36 62 06-07-79 27 0 21-3 0 88 28 06-21-79 27 9 10 24 53 07-06-79 8 3 832 0 0- 57 07-19-79 9 4 261 1 25 52 08-09-79 1 32 6 6 67 55 56 105 0843-79 21 7 286 3 91 I I I. APPENDIX C I I I I I I to I I . . I I . I I I I I1 -1 I I Othello Silt Loam C1 Horizon Profile Description Al 0 to 2 inches, dark grayish brown (2.5Y 4/2) silt loam, very weak medium granular structure, friable, slightly sticky, very strongly acid, abrupt smooth boundary. A2g 2 to 16 inches, light gray (2.5Y 712) silt loam with common medium dis- tinct yellowish brown (10YR 5/8) mottles, weak medium granular structure friable, slightly sticky, very strongly acid, clear smooth boundary. B2g 16 to 28 inches, grayish brown (2.5Y 5/2) silty clay loam with common coarse distinct yellowish brown (10YR 5/6) and a few medium distinct mottles of strong brown (7.5 YR 5.6), moderate medium subangular blocky structure, friable, sticky, continuous clay films, very strongly acid, clear wavy boundary. B 28 to 34 inches, light gray (5Y 712) silt loam with many medium distinct yellowish brown (10YR 5/8) mottles, weak medium subangular blocky structure, friable and slightly sticky, some dark gray coats in large cracks, very strongly acid, clear wavy boundary. 11 34 to 40 inches, grayish brown (10 YR 5/2) and dark gray (10YR'4/1) loam with about 15 percent small rounded gravel, common medium distinct yellowish brown (10 YR 5/6) mottles, massive to very weak medium subangular blocky structure, friable, slightly sticky, very strongly acid, clear to abrupt smooth boundary. Ilcg 40 to 55 inches, light brownish gray (2.5 Y 6/2) loamy sand with about 20 percent rounded gravel, coarse blotches of yellowish brown (10 YR 5.6) single grained, loose to very friable, very strongly acid. Site Characteristics Location: Dorchester County: Center for Environmental and Estuarine Studies, 3 miles west of Cambridge, Maryland, woods on east side of road between Horn Point Road and Route #343, 3/8 mile north of inter- section with Route #343 Vegetation: Loblolly pine, sweet gum, black gum, and red maple Parent Material: Coastal Plain sediments, silty materials over sands Physiography: Coastal Plain Slope: less than 1 percent Elevation: 12 feet Drainaqe: Poorly drained Permea6i ity: Moderate Root distr-i-Eution: Few small roots down to IIc. Moiture: Ground Water 45 inches Date: December 15, 1976 Description by: Richard L. Hall Mattapex Silt Loam C2 Horizon Profile Description Ap 0-10 inches, very dark grayish brown (10YR 3/2) silt loam, weak medium granular structure, very friable, mildly alkaline, abrupt smooth boundary. BI 10-15 inches, yellowish brown (10YR 5/4) silt loam, weak medium sub- angular blocky structure, friable, very dark grayish brown filled worm holes, mildly alkaline, clear smooth boundary. B21 15-24 inches, light yellowish brown (10YR 6/4) silt loam, moderate medium subangular blocky structure, friable, grayish brown thin coats #d filled old root channels, mildly alkaline, clear smooth boundary. B22 24-30 inches, pole brown (10YR 6/3) silt loam, common medium distinct light gray (5Y 6/1) and a few medium distinct strong brown (7.5 YR 5/8) mottles, moderate medium subangular blocky structure, friable, discon- tinuous clay films, mildly alkaline, abrupt wavy boundary. IIB23g 30-34 inches, grayish brown (2.5YR 5/2) loam, common medium distinct light gray (2.5YR 712) and brownish yellow (10YR 6/6) mottles and few pockets of dark gray (N 4/0), weak coarse angular structure parting to moderate medium subangular blocky, firm, continuous clay films and compressed roots in large cracks, moderately alkaline, clear wavy boundary. IIAg 34754 inches, dark grayish brown (10YR 4/2) sandy loam, common medium faint pole brown (10YR 6/3) and a few coarse distinct strong brown (75YR 5/8) mottles, massive in place parting to weak medium subangular blocky structure when disturbed, firm in place, pockets of light brownish gray (10YR 6/2) friable loamy sand, about 15 percent rounded gravel coated with thin clay films, mildly alkaline, clear wavy boundary. IIIB2g 54 to 69 inches, light gray (2.5Y 712) silty clay loam, many medium distinct strong brown (7-5 YR 5/8) and olive gray (5Y 5/2) mottles, weak coarse subangular blocky structure parting to moderate fine sub- angular blocky, friable, discontinuous clay films and dark grayish brown (2.5Y 4/2) filled old root channels, mildly alkaline. Site Characteristics Location: Dorchester County, Center for Environmental and Estuarine Studies 3 miles west of Cambridge, Maryland, 2000 feet north of Horn Point Road and 50 feet east of enterance road. VeRttation: Corn stubble Parent Material: Coastal Plain Sediments, silts over medium textured materials - C Physiography. oastal Plain Slope: less than 1 percent ETevation: 13 feet Drainage: Moderately well drained Permeability: Moderate Richard L. Hall Soil Scientist C3 Bertie Silt Loam Horizon Profile Description Ap 0-8 inches dark grayish brown (10YR 4/2) silt loam, moderate fine granular structure; friable; medium acie; abrupt smooth boundary. B21 8-15 inches light yellowish brown (2.5Y 6/4) heavy silt loam; faint brown (10 YR 5/2) and light brownish gray (10YR 6/2) mottles; weak medium sub- angular blocky structure; friable; grayish brown clay skins; slightly acid; clear smooth bounddry. B22 15-25 inches light yellowish brown (2.5Y 6/4) heavy silt loam; common medium brownish yellow (IOYR 6/6) and light brownish gray (10YR 6/2) mottles; weak medium subangular blocky structure; friable; light olive brown clay skins slightly acid, gradual boundary. B3g 25-32 inches light gray (5Y 6/1) silt loam; common fine distinct strong brown (7.5 YR 5/6) and a few coarse faint gray (5Y 5/1) mottles; weak medium subangular blocky structure; firm; medium acid; clear smooth boundary. IIA-B 32-45 inches; dark gray (IOYR 4/1) heavy gravelly loam common meidum dis- tinct strong brown (7.5YR 5/6) and brown (7.5YR 5/4) mottles, weak medium subangular blocky structure; friable; very strongly acid; clear smooth boundary. IIA-B 45-52 inches; very dark grayish brown (10YR 3/2) gravelly loam; common coarse distinct grayish brown (10YR 5/2) mottles; weak coarse subangular blocky structure; friable; very strongly acid; clear smooth boundary. IIICg 52-60 inches; light gray (2-5Y 712) silty clay loam; common medium pro- minent strong brown (7.5YR 5/8) and common coarse distinct brown (7.5YR 5/2) mottles; structureless, massive; friable; extremely acid. Site Characteristics Location: Dorchester County, Center for Environmental and Estuarine Studies 3 miles west of Cambridge, Maryland, 100 feet north of Horn Point Road and 100 feet east of main entrance road. Vegetation: Corn stubble. Parent material: Coastal Plain sediments; silts over medium textured materials. Physiography: Coastal Plain Slope: less than 1 percent Elevation: 12 feet Drainaqe: Somewhat poorly drained Permeability: Moderate Root distribution: few below 15 inches Moisture: Moist Described by: R.L. Hall Date: November 11, 1976 Map Legend for Soils maps C4 �ymbol Soi1 Type BoA Bertie milt loam, 0 to 2 percent slopes BcB Bertie milt loam, 2 to 5 percent slopes Bec Bertie milt loam, 5 to 15 percent slopes Bx Bibb silt loam MsA Mattapex silt loam, 0 to 2 percent slopes MaB Mattapex silt. loam, 2 to 5 percent slopes MsC Mattapex silt loam,, 5 to 15 percent slopes OhA Othello silt loam, 0 'to 2 percent slopes OhB Othello silt loam, 2 to 5 percent slopes OhC Othello silt loam, 5 to 15 percent slopes Ot Othello silt loam, possibility Xof ponded water Su Sulfihemist WoA Woodstown loam, 0 to 2 percent slopes WoB Woodstown loam, 2 to 5 percent slopes Woc Woodstown loam, 5 to 10 percent slopes Special-Symbols Pond - Pond Fill - Fill #Kitchen midden Wet spot Peremial stream Drainage ditch, not crossable with farm machinery Gravel C5 C:v re lee- 01 del !k Soils map of agricultural areas, HPEL. C6 0'Ix @Oo Soils map of wooded land, HPEL. C7 DRILLN LOG Max. Depth Hole A-17 Geologist: Christy Date: 4-12-77 Augered 10, Location: Approximately 82' South-west of Md. State Wildlife.building, at the side of the road Wall Soil Casing SoiL DEscgipnm Column Depth 0 to 3' Gray-brown SILT, with some Clay and a trace 01 of fine Sand 3' to 3.11' Light brown SAND, with some Silt and a trace of Clay 2 3;j to 611' Light, cream-brown SILT, with some fine Sand and some Clay. Ratio of silt and fine sand variable in any one zone I 3 NOTE: water filling hole at about 5'. 612 to 10' Light, gray-brown SILT with fine Sand and 4 a trace of Clay. 7.' 6. 7 8 9 Jo/ C8 DRILING LOG Max. Depth Hole W-25 Geologist: Christy Date :3-23-77 Augered 10, Location: Approximately 1250 ft. West of the turn in Lover's lane. Wall Soil Casing SoiL DEscginn Column Depth 0 0 to 2k' Gray-brown, mottled SILT, with some Clay and a trace of fine Sand NOTE: water seepage filled hole at about 21-2' 2@ to 3' Gray-brown, mottled SILT, with Sand and a trace of Clay 2 NOTE: this is a transitional zone 3 to 4' Yellowish-brown, mottled SAND, with a trace 3 of Silt NOTE: some gravel, but less than 4% 4 to W Yellowish-brown mottled SAND- SILT transition 4.1-, to io' Gray-brown mottled SILT, with some Clay and a trace of fine Sand. . Very tight and difficult augering. 6 7 9 10 C9 DRILLING LOG ax. ep h Hole W-42 Geologist: Christy and Jones Date: -,-77 Augered 9.8' Location: Approximately 650' east of Lover's Lane on Rt. 343 34' north from edge of woods Wall Soil Casing SOIL DESCRIPTION Column Depth 0-2@' Gray brown SILT, mottled, some Clay and trace of 0 fine Sand 215'-3' Gray brown SILT with some Sand, some Clay and a 1@/ trace of Gravel 2'-3Yt.' Very light brown SILT with some Sand, trace of 2 Gravel 3@4 -9@4' Gray brown SILT with some Clay trace of Sand NOTE: somewhat moist at 7' color chinge at 8y4' light chocolate brown brightly mottled with some gray 5 7- a 9 10 C10 DRILING a Max. Deptfi iiale W- 149 Geologist:. Christy Date: 9-15-77 Augered 9 3/4' Location: Approximately 84' South-west of Horn Point Road. Along woods Lane opposite the Golf Course Road. and 24' east of lane Wall Soil Casing SOIL DESCRIPTION Column Depth 0 0 to 2Y Gray-brown mottled SILT, with some Clay and a trace of,fine Sand 2@2- to 2Y4' Light brown, lightly mottled SILT, with some Clay and some Sand (Transitional layer) 2 2Y4 to 5h' Lightbrown SAND, with some Silt and a trace of Clay NOTE: this deposit has alternating layers, the more sand rich are light brown and the more silt rich are brightly mottled. Each layer is about 6"thick 5@ to 71 Light brown to gray blue SAND, with a trace of SILT 5d -7 7 to 8' Uniform dark blue gray SAND, with a trace of Silt NOTE: Seepage at about 7' 8 to 9' Uniform dark blue-gray SAND with some silt and a trace of Clay 7 NOTE: silt in several lenses at a higher percent than Sand 1oL__ 1111011111milmol 3 6668 00000 8724