Water Resources Investigations Report 96-4288 "Ground-water quality and its relation tohydrogeology, land use, and surface-water quality in the Red Clay Creek Basin, piedmont Physiographic Province, Pennsylvania and Delaware" by L.A. Senior       The Red Clay Creek Basin in the Piedmont Physiographic Province of Pennsylvania and Delaware is a 54-square-mile area underlain by a structurally complex assemblage of fractured metamorphosed sedimentary and igneous rocks that form a water-table aquifer. Ground-water-flow systems generally are local, and ground water discharges to streams. Both ground water and surface water in the basin are used for drinking-water supply.       Ground-water quality and the relation between ground-water quality and hydrogeologic and land-use factors were assessed in 1993 in bedrock aquifers of the basin. A total of 82 wells were sampled from July to November 1993 using a stratified random sampling scheme that included 8 hydrogeologic and 4 land-use categories to distribute the samples evenly over the area of the basin. The eight hydrogeologic units were determined by formation or lithology. The land-use categories were (1) forested, open and undevloped; (2) agricultural; (3) residential; and (4) industrial and commerical. Well-water samples were analyzed for major and minor ions, nutrients volatile organic compunds (VOC's), pesticides, polychlorinated biphenyl compounds (PCB's), and radon-222.       Concentrations of some constituents exceeded maximum contaminant levels (MCL) or secondary maximum contaminant levels (SMCL) establisehd by the U.S. Environmental Protection Agency for drinking water. Concentrations of nitrate were greater than the MCL of 10 mg/L (milligrams per liter) as nitrogen (N) in water from 11 (13 percent) of 82 werlls sampled; the maximum concentration was 38 mg/L as N. Water from only 1 of 82 wells sampled contained VOC's or pesticides that exceeded a MCL; water from that well contained 3 ug/L chlordane and 1 ug/L of PCB's. Constituents or properties of well-water samples that exceeded SMCL's included iron, manganese, dissolved solids, pH, and corrositvity. Water from 70 (85 percent) of the 82 wells sampled contained radon-222 activities greater than the proposed MCL of 300 pCi/L (picoCuries per liter).       Differences in selected major and minor ion concentrations and radon-222 activites were statistally significant between some lithologies and are related to differences in mineralogy. Ground water from felsic gneiss and schist generally contained higher radon-222 activities than the other lithologies; activities as high as 10,000 pCi/L were measured in a water sample from the felsic geniss.       Flow-routing studies were made to evaluate the response of the Lehigh and Delaware Rivers to low-flow augmentative releases from two reservoirs --Francis E. Walter Reservoir and Beltzville Lake--in the Lehigh River basin. Digital routing models that use diffusion-analogy methods to convolute flows with system-response functions were developed to simulate daily flows at selected sites. Model errors, for five sites and for peridos of 1 year or more, were mostly between 3 and 12 precent in terms of absolute errors in daily flows and were mostly within 4 percent for flow volumes.       The developed models were satisfactory for predicting hydrographic response at eight sites in the reach from White Haven, Pennsylvania to Trenton, New Jersey. However, abrupt changes in the flow rate of the Lehigh River at the Bethlehem and the Glendon gaging stations could not be adequately replicated with the model. The model tends to underestimate peaks by as much as 30 percent and to overestimate some low flows of short duration by as much as 20 percent. This occurs primarily because inflows from ungaged areas could not be reliably modeled throughout their ranges by use of flow records for gaged streams. The model will underestimate long-duration low flows at the Glendon site for periods when underflows at the gaging stations on Little Lehigh and Monocacy Creeks are significant.       The models were used to route hypothetical releases from Francis E. Walter Reservoir during a low-flow period. The model for the Lehigh River indicated that an added release of 50 ft3/s (cubic feet per second) over a 64-day period during the severe drought in the summer of 1965 would have increased minimum flows for this period at Bethlehem and Glendon by approxi- mately the same amount. A hypothetical release of 200 ft3/s for the period July 20-22, 1965, which is about eight times the actual release in this period, would have been attenuated by about 25 percent when it reached the Bethlehem gage. The synthesized hydrograph for the Bethlehem gage showed such a release would have passed their by July 27. Unresolvable timing errors in the models created an unrealistic hydrographic response for this release at the Trenton gage; but, such a release probably would have passed Trenton by July 29.       In order to time the movement of a release wave more accurately than could be done with the developed model, travel times for the wave of an augmentative low-flow release were obtained by field observations and compar- isons of gage-height records. The observed leading edge of an abrupt release of 153 ft3/s from Francis E. Walter Reservoir, which ended a 2-day release at a rate of 48 ft3/s, arrived at the gage below the reservoir in 0.5 hour, at White Haven in 3.7 hours, at the mouth of Pohopoco Creek in about 23.1 hours, at Walnutport in 27 hours, at Bethlehem in 39 hours, and at Glendon in 42 hours.       This release could not be detected in the record for the Trenton gage. Travel time for an augmentative release in the Lehigh River is dependent upon the pre- release discharge, the relative magnitude of the release, and antecedent rain- fall. Relationships are provided for estimating the time of arrival at Walnutport, Bethlehem, and Glendon of the leading edge of waves generated by autmentative releases of 75 to 600 ft3/s. Stage observations on Pohopoco Creek indicated a 2.1-hour travel time between Beltzville Lake and the Lehigh River for the elading edge of a wave produced by a typical augmentative release from this reservoir.       Differences in the concentrations of nitrate, sodium, and chloride, and the frequency of pesticide detections in ground water were statistaclly significant between samples from wells in some land-use categories. Concentrations of nitrate can be attributed to the use of fertilizers on the land surface and other agricultural activities. Much of the industrial and commercial land use is in areas previously used for or related to mushroom production. Concentrations of chloride and sodium also were greatest in water from wells in agricultural and industrial and commercial areas, probably because of the use of fertilizer and road salt. Concentrations of nitrate, chloride, and sodium in water samples from wells in forested and residential land use did not differ statistically signifiantly from each other. The herbicides metolachlor and atrazine were the most frequently detected pesticides and were detected more frequently in agricultural areas than in areas with other land uses; their presence is related to their use in crop production. VOC's were detected infrequently and only in residential and industrial and commercial areas.       The relation between ground-water quality and surface-water quality is assessed by comparing nitrate and chloride concentrations in the 1993 ground-water samples and 1993-94 base-flow samples. Base-flow samples were collected at eight stream sites in the headwaters of the West Branch of Red Clay Creek in 1994 and at two long-term stream-monitoring sites on the East and West Branches of the Red Clay Creek in 1993-94. The average concentrations of chloride and nitrate in ground-water samples from wells in areas above the headwater stream sites and two long-term stream-monitoring sites were similar to the concentrations of chloride and nitrate in base flow at those sites. An observed increase in nitrate concentration in base flow at the long-term monitoring site on the West Branch of Red Clay Creek from 1970 to 1995 may be related to an increase in nitrate concentrations in ground water in that area of the basin. Return to the Water Resources of Pennsylvania Home Page or go directly to: The URL for this page is http://pa.water.usgs.gov /abstracts/wrir_96-4288.html Please note our privacy statement and disclaimer Accessibility Answers to many common questions can be found on our Frequently Asked Questions (FAQ) page. 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