Geology topics

Research about Conestoga River headwaters

Source-linked reports with geographic coverage including Conestoga River headwaters.

5 recordsLinked to original sources

USGS1997

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania: Hydrology of a small carbonate site near Ephrata, Pennsylvania, prior to implementation of nutrient management

The U.S. Geological Survey, in cooperation with the U.S. Department of Agriculture and Pennsylvania Department of Environmental Protection, investigated the effects of agricultural best-management practices on water quality in the Conestoga River headwaters watershed. This report describes environmental factors and the surface-water and ground-water quality of one 47.5-acre field site, Field-Site 2, from October 1984 through September 1986, prior to implementation of nutrient management. The site is partially terraced agricultural cropland underlain by carbonate rock. Twenty-seven acres are terraced, pipe-drained, and are under no-till cultivation. The remaining acreage is under minimum-till cultivation. Corn is the primary crop. The average annual rate of fertilization at the site was 480 pounds per acre of nitrogen and 110 pounds per acre of phosphorus. An unconfined limestone and dolomitic aquifer underlies the site, Depth to bedrock ranges from 5 to 30 feet below land surface. Estimated specific yields range from 0.05 to 0.10, specific capacities of wells range from less than 1 to about 20 gallons per minute per foot of drawdown, and estimates of transmissivities range from 10 to 10,000 square feet per day. Average ground-water recharge was estimated to be about 23 inches per year. The specific capacity and transmissivity data indicate that two aquifer regimes are present at the site. Wells drilled into dolomites in the eastern part of the site have larger specific capacities (averaging 20 gallons per minute per foot of drawdown) relative to specific capacities (averaging less than 1 gallon per minute per foot of drawdown) of wells drilled into limestones in the western part of the site. Median concentrations of soil-soluble nitrate and soluble phosphorus in the top 4 feet of silt- or silty-clay-loam soil ranged from 177 to 329 and 8.5 to 35 pounds per acre, respectively. Measured runoff from the pipe-drained terraces ranged from 10 to 48,000 cubic feet and was 1.7 and 0.8 percent, respectively, of the 1985 and 1986 annual precipitation. An estimated 90,700 cubic feet of surface runoff carried 87 pounds to total nitrogen and 37 pounds of total phosphorus, or less that 0.65 percent of the amount of either nutrient applied during the study period. Rainfall on the snow-covered, frozen ground produced more that half of the runoff and nitrogen and phosphorus loads measured in pipe-drained runoff. Graphical and regression analyses of surface runoff suggest that (1) mean-storm concentrations of total nitrogen species and total phosphorus decreased with increasing time between a runoff event and the last previous nutrient application, and (2) mean total-phosphorus concentrations approached a baseline value (estimated at 2 to 5 milligrams per liter for total-phosphorus concentrations) after several months without nutrient applications. Dissolved nitrate concentrations in ground water in wells unaffected by an on-site ammonia spill ranged from 7.4 to 100 milligrams per liter. Average annual additions and removals of nitrogen were estimated. Nitrogen was added to the site by applications of manure and commercial fertilizer nitrogen, as well as by precipitation and ground water entering across the western site boundary. These sources of nitrogen accounted for 95, 3, 1, and 1 percent, respectively, of estimated additions. Nitrogen was removed from the site in harvested crops, by ground-water discharge, by volatilization, and in surface runoff, which accounted for 42, 28, 29, and less than 1 percent, respectively, of estimated removals.

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USGS1997

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania: Effects of nutrient management on quality of surface runoff and ground water at a small carbonate-rock site near Ephrata, Pennsylvania, 1984-90

The U.S. Geological Survey and the Pennsylvania Department of Environmental Protection conducted a study from 1984 to 1990 to determine theeffects of the implementation and practice of nutrient management [an agricultural best-management practice (BMP)] on the quality of surface runoff and ground water at a 55-acre crop and livestock farm in carbonate terrain nearEphrata, Pa. Implementation of nutrient management at Field-Site 2 resulted in application decreases of 33 percent for nitrogen and 29 percent for phosphorus. There wereno significant changes in nitrogen or phosphorusloads for a given amount of runoff from the pre-BMP to the post-BMP periods. However, less than 2 percent of the applied nutrients weredischarged with runoff throughout the study period.After the implementation of nutrient management, statistically significant decreases in concentrations of nitrate in ground-water samples occurred at threeof the four wells monitored throughout the pre- and post-BMP periods. The largest decreases in nitrate concentrations occurred at wells where samples hadthe largest nitrate concentrations prior to nutrient management. Changes in nitrogen applications to the contributing areas of five wells were correlated with nitrate concentrations of the well water. The correlations between the timing and amount of applied nitrogen and changes in ground-water quality met the four conditions that are characteristic of a cause-effect relation: an association, consistency, responsiveness, and a mechanism. Changes in ground-water nitrate concentrations lagged behind changes in loading of nitrogen fertilizers (primarily manure) by approximately 4 to 19 months.

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USGS1997

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania: A summary report, 1982-90

Pipe-outlet terracing was effective in reducing sediment losses from a field site, but total nitrogen and phosphorus losses with runoff were not significantly different before and after terracing. Median concentrations of dissolved nitrate in several ground-water sampling locations increased after terrace installation. Dissolved nitrate concentrations in ground water decreased significantly after nutrient-management implementation. Findings indicate that agricultural-management practices to improve water quality are most effective if their overall design effects on surface- and ground-water systems are considered in their design.

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USGS1996

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania: Characterization of surface-runoff and ground-water quantity and quality in a small carbonate basin near Churchtown, Pennsylvania, prior to terracing and implementation of nutrient management: Water-quality study of the Conestoga River headwaters, Pennsylvania

The U.S. Geological Survey, in cooperation with the Pennsylvania Department of Environmental Protection1 , conducted a study as part of the U.S. Department of Agriculture's Rural Clean Water Program to determine the effects of agricultural best-management practices on surface-water and ground-water quality in the Conestoga River headwaters basin. This report describes Field-Site 1 and characterizes the surface-runoff and ground-water quantity and quality at the site from January 1983 through September 1984, before the implementation of terracing and nutrient-management best-management practices. The 22.1-acre site, part of two dairy farms, was cropland used primarily for the production of corn and alfalfa, and is underlain by carbonate rock. During the 21-month study period, 91.2 inches of precipitation fell, of which 66 percent occurred during the 1984 water year. Of the 169 storms of 0.10 inch or larger, 97 produced measurable runoff. The average annual application of nutrients to the 14.4 acres of cornfields was 410 pounds per acre of nitrogen and 110 pounds per acre of phosphorus. About three times more nutrients were applied during 1984 water year than during the 1983 water year. The approximate soil-nitrate concentration as nitrogen for the study period was 8.2 milligrams per kilogram in the top 8 inches of soil. Runoff for the study period totalled 714,000 cubic feet, or 9.8 percent of total precipitation. Eighty-eight percent of the runoff occurred during the 1984 water year. Regression analyses indicate that total runoff was controlled primarily by total precipitation amounts during storms and by antecedent moisture conditions; mean event and maximum instantaneous discharges are controlled by precipitation intensity and by antecedent moisture conditions. Regression analyses also suggest that crop cover on the corn acreage affected runoff amounts and rates. Mean concentrations in runoff ranged from 24 to 73,000 milligrams per liter for suspended sediment, 0.45 to 24 milligrams per liter for total phosphorus, and 1.5 to 55 milligrams per liter for total nitrogen. Of the total nitrogen in instantaneous runoff samples, a median of 72 percent was total organic nitrogen. Results of multiple regression analyses suggest that mean nitrogen concentrations in runoff (1) increased with increased surface-nitrogen applications made prior to runoff, and (2) were diluted with increased precipitation duration. Runoff from storms on frozen ground produced the highest loads of nitrogen in runoff. Over the 21-month study period, an estimated 258 tons of suspended sediment, 314 pounds of nitrogen, and 176 pounds of phosphorus were transported with runoff from the site. Of this, 88 percent of the nitrogen and phosphorus loads and 94 percent of the suspended-sediment load were discharged during the wet 1984 water year. The loads for the study period represent 2.5 percent of the total nitrogen and 5.5 percent of the total phosphorus applied to the site as manure and commercial fertilizer. The ground-water basin at the site is slightly larger than the surface-water basin. Ground-water levels, except at one well, responded quickly to recharge; water levels peaked several hours to a day after precipitation. Surface-applied materials moved rapidly to the water table through macropores and slowly by transport through micropores in the unsaturated zone. Median concentrations of dissolved nitrate ranged from 9.2 to 13 milligrams per liter as nitrogen for ground-water samples collected monthly from five wells and a spring. Dissolved nitrate comprised 93 percent (median percentage) of the total nitrogen in ground-water samples. The effect of recharge on ground-water nitrate concentrations was affected by variations in nutrient availability at the land surface and in the unsaturated zone. A lag time of 1 to 3 months was observed between the time that nitrogen was applied to the land surface and local maximums in nitrate concentrations were detected in ground water unaffected by recharge events. Approximately 3,187,000 cubic feet of ground water and an associated 2,200 pounds of nitrate-nitrogen discharged from the site during the study period. For the study period, 42 percent of the precipitation recharged to ground water, 10 percent became runoff, and 48 percent evapotranspired. Inputs of nitrogen to the study area were estimated to be 93 percent from manure, 5 percent from commercial fertilizer, and 2 percent from precipitation. Nitrogen outputs from the system were estimated to be 38 percent to crop uptake, 39 percent to volatilization, 20 percent to ground-water discharge, and 3 percent to surface runoff.

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USGS1996

Evaluation of agricultural best-management practices in the Conestoga River headwaters, Pennsylvania: Effects of nutrient management on water quality in the Little Conestoga Creek headwaters, 1983-89

Water quality in the headwaters of the Little Conestoga Creek, Lancaster County, Pa., was investigated from April 1986 through September 1989 to determine possible effects of agricultural nutrient management on water quality. Nutrient management, an agricultural Best-Management Practice, was promoted in the 5.8-square-mile watershed by the U.S. Department of Agriculture Rural Clean Water Program. Nonpoint-source- agricultural contamination was evident in surface water and ground water in the watershed; the greatest contamination was in areas underlain by carbonate rock and with intensive row-crop and animal production. Initial implementation of nutrient management covered about 30 percent of applicable land and was concentrated in the Nutrient-Management Subbasin. By 1989, nutrient management covered about 45 percent of the entire Small Watershed, about 85 percent of the Nutrient- Management Subbasin, and less than 10 percent of the Nonnutrient-Management Subbasin. The number of farms implementing nutrient management increased from 14 in 1986 to 25 by 1989. Nutrient applications to cropland in the Nutrient- Management Subbasin decreased by an average of 35 percent after implementation. Comparison of base- flow surface-water quality from before and after implementation suggests that nutrient management was effective in slowing or reversing increases in concentrations of dissolved nitrate plus nitrite in the Nutrient-Management Subbasin. Although not statistically significant, the Mann-Whitney step-trend coefficient for the Nutrient-Management Subbasin was 0.8 milligram per liter, whereas trend coefficients for the Nonnutrient-Management Subbasin and the Small Watershed were 0.4 and 1.4 milligrams per liter, respectively, for the period of study. Analysis of covariance comparison of concurrent concentrations from the two sub- basins showed a significant decrease in concen- trations from the Nutrient-Management Subbasin compared to the Nonnutrient-Management Subbasin. The small, positive effect of nutrient management on base-flow water quality should be interpreted with caution. Lack of statistical significance for most tests, short-term variation in climate and agricultural activities, unknown ground-water flow rates, and insufficient agricultural-activity data for farms outside of the Nutrient-Management Subbasin were potential problems. A regression model relating nutrient applications to concen- trations of dissolved nitrate plus nitrite showed no significant explanatory relation.

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