Ground-Water Flow, Geochemistry, and Effects of Agricultural Practices onNitrogen Transport at Study Sites in the Piedmont and Coastal Plain Physiographic Provinces, Patuxent River Basin, Maryland

摘要

The report describes the flow and geochemistry of ground water and the transportof nitrogen at two study sites in the Patuxent River Basin in Maryland. Ground-water data are presented for the period from August 1986 through June 1992. Characteristics of aquifers, directions and rates of ground-water flow, and relations among different components of flow through the study sites are described. Ground-water flow is simulated by use of numerical models. Simulated ground-water flow is compared to measured precipitation and surface runoff and to other unmeasured flow components, including evapotranspiration and storage and interflow in the unsaturated zone. The chemical composition of ground water at the study sites is described. Possible chemical-weathering reactions and solute-transport processes are examined to account for the observed major-ion composition of the water. Nitrogen concentrations in surface runoff, soil water, and ground water are analyzed to determine the effects of agricultural practices and other factors on nitrogen transport at the study sites. Spatial and temporal distributions of nitrogen concentrationa re examined to infer controls on nitrogen transport, and nitrogen loads in surface runoff and ground water are estimated by using nitrogen-concentration and flow data.