COMPARISON OF FIVE REGIONAL GROUND-WATER STUDIES

A comparison of the ground-water conditions for regional aquifers in the northeastern and north-central United States was conducted to contrast the ground-water-resources issues in the Great Lakes and New England areas. Regional Aquifer-System Analysis (RASA) studies conducted between 1978 and 1995 by the U.S. Geological Survey provided quantitative assessments of 25 of the most important regional aquifer systems in the United States. The studies were conducted in response to concerns about lowered water levels and reductions in ground-water storage in response to large-scale ground-water withdrawals and drought conditions. Five of these studies were located in the northeastern and north-central parts of the United States: the Northern Midwest, Michigan Basin, Midwest Basins and Arches, North Atlantic Coastal Plain, and Northeast Glacial Valleys aquifer systems. Based on these studies, the effects of large-scale ground-water withdrawals differ among the regional systems. For example, intrusion of saline water into freshwater aquifers is an important issue along the Atlantic Coastal Zone as well as in the Michigan Basin systems. Ground-water/surface-water interaction is particularly important in the Northeast Glacial Valleys system. Comparison of water budgets and issues related to water availability from these studies is helping to formulate a new series of issue-based regional ground-water assessments that are being conducted as part of the U.S. Geological Survey's Ground-Water Resources Program.