Preliminary evaluations of regional ground-water quality in relation to land use

The U.S. Geological Survey through its Toxic-Waste— Ground-Water Contamination Program began studies during 1984 to evaluate the degradation of regional ground-water quality as a result of human activities. The studies are designed to quantitatively relate human activities, expressed as land use, to the quality of ground water at a regional scale. Preliminary results from six of the studies in New York, New Jersey, Connecticut, Florida, Nebraska, and Colorado summarized in this paper indicate that regional ground-water quality has been affected by human activities. The frequencies of detection of volatile organic compounds and some trace elements were larger in ground water underlying urban or industrial areas in comparison to undeveloped areas. Ground water in agricultural areas generally had larger concentrations of nitrate and had an increased frequency of detection of pesticides in comparison to undeveloped areas. Effects of human activities on water quality increased as the intensity of urbanization or irrigation increased. Ground-water pumpage, waste-water discharges into a stream that is hydraulically connected to an alluvial aquifer, and consumptive use of ground water affected the ground-water quality in one study area to a greater extent than land-use practices. These preliminary results indicate that in specific areas, surficial nonpoint sources, expressed as land use, have altered regional ground-water quality. Additional studies are being made to determine if these results are consistent and widespread.