Ground‐Water Recharge and Its Effects on Nitrate Concentration Beneath a Manured Field Site in Pennsylvania

Abstract

Ground‐water recharge to a shallow, unconfined, fractured dolomite aquifer underlying agricultural land in Lancaster County, Pennsylvania occurs by two mechanisms. Direct recharge occurs through pathways such as near‐surface bedrock fractures and sinkholes, and affects dissolved nitrate concentration of ground water within two to three days; its effects last only about one week. Gradual recharge occurs through small channels and pores in the unsaturated zone and affects dissolved nitrate concentration for several weeks or more after the effects of direct recharge have dissipated. Whether recharge causes an increase or decrease in dissolved nitrate concentration depends on the amount of nitrogen‐rich manure spread on the site prior to the storm. Direct recharge from a storm in March 1984, a month in which 18 tons of manure were spread, resulted in a rapid decrease in dissolved nitrate concentration of about 2.5 milligrams per liter (mg/1) as nitrogen. Direct recharge from a storm in May 1984, after 384 tons of manure had been spread in April, resulted in a rapid increase in dissolved nitrate concentration of about 3 mg/1 as nitrogen. Concentration changes caused by gradual recharge several weeks or more after the storms were of the same magnitude as those caused by direct recharge during the storm.

Ground-water flow, geochemistry, and effects of agricultural practices on nitrogen transport at study sites in the Piedmont and Coastal Plain physiographic provinces, Patuxent River basin, Maryland

“…Additionally, the unsaturated zone is thinner and probably more permeable at the Coastal Plain site than at the Piedmont site, and flow velocities in the zone probably are faster and traveltimes shorter. For comparison, faster recharge than that found at either of the sites for this study was observed throughout the year in an agricultural area underlain by a karst flow system in Pennsylvania (Gerhart, 1986;Hall, 1992b), where water percolates through sinkholes and bedrock fractures enlarged by solution weathering. Storage of the water in the unsaturated zone and removal by evapotranspiration were probably larger at both study sites than in karst areas.…”

Spatio‐temporal analysis of groundwater recharge and mound dynamics in an unconfined aquifer: a GIS‐based approach

“…A number of studies (Swamee and Ojha, 1997) attempted to simplify the existing solutions, but the resulting equations are still too complicated for routine applications in recharge basin design and require an iterative solution. The water-table fluctuation (WTF) method has been used in various studies (Gerhart, 1986;Hall and Risser, 1993), and is found to be best applied over short time periods in regions having shallow water-tables that display sharp rises and declines in water levels. The present study employs the theories of distribution of mound rise obtained from the WTF method and groundwater volume balance residual by Darcy law (Bear, 1979) in the aquifer system.…”

Geohydrology, water availability, and water quality of Jefferson County, West Virginia, with emphasis on the carbonate area

“…The beds of shaly limestone, shales, and sandy limestones in the Conococheague Formation (Grimsley, 1916, p. 287) tend to be less permeable than limestone and may cause the mounds in the Conococheague Formation. BEEKMANTOWN LIMESTON 197019711972197319741975197619771978197919801982198319841985198619871989 Figure 6.--Noon daily water levels at well 20-5-7 at Martinsburg, West Virginia, showing seasonal fluctuations and approximate water levels at time water-quality samples were collected. …”