Regional Groundwater Declines in the Atlantic Coastal Plain Aquifer System

The Atlantic Coastal Plain aquifer system underlies more than 100,000 mi² of the east coast of the United States, extending from Long Island, New York, to northern Florida and is the predomi­nant source of water for more than 20 million people. Over the last century the aquifer system has been developed extensively over wide areas resulting in substantial declines in water levels and areas of salt-water intrusion, raising concerns regarding the sustainability of the water supply in places.

To define areas of past and current declines in ground-water levels, as well as to document changes in those levels, historical water-level data from more than 4,000 wells completed in 13 regional aquifers in the Atlantic Coastal Plain were evaluated. Regional water-level change maps for intervals spanning predevelopment time (generally about 1900 or earlier) to circa 1980, and circa 1980 to circa 2000 have been developed and provide a broad view of the effects of ground-water development and conservation measures across the region.

From predevelopment to 1980, water-level declines of more than 100 ft were common in the Atlan­tic Coastal Plain with declines of as much as 200 feet or more in areas of east central New Jersey, southern Virginia and southwestern Georgia. Water-level data for the period 1980 to 2000 show that conservation measures have served to limit with­drawals in some affected areas, moderating or stabilizing water-level decline, and in some cases, resulting in substantial recovery. In other cases, increases in ground-water withdraw­als have resulted in continued rapid water-level declines. The nature of regional water-level changes within specific aquifers are evaluated on the basis of available water-use data. Regional variability in water-level change in the Atlantic Coastal Plain aquifer system is the result of regional differences in aquifer properties as well as changing pat­terns of ground-water withdrawals.