Emerging Information on Groundwater of the Virginia Eastern Shore

Presentation: PowerPoint

Author(s): E. Randolph McFarland Hydrogeologist Virginia Water Science Center U.S. Geological Survey

Abstract: Understanding of groundwater conditions on the Virginia Eastern Shore is being advanced by a revision of the hydrogeologic framework, improved characterization of buried paleochannels, and delineation and monitoring of the saltwater-transition zone. Groundwater withdrawals from the shallow sole-source aquifer system have lowered water levels and increased the potential for saltwater intrusion. Withdrawals are regulated by the Virginia Department of Environmental Quality (VA DEQ) using a computer model, but which is based on outdated information. Using newly compiled borehole data, the U.S. Geological Survey in cooperation with the VA DEQ is delineating complex spatial relations between confined aquifers and deeply incised paleochannel sediments. Moreover, and based on spatial analysis of groundwater chemical-quality samples, the saltwater transition zone has been found to exhibit a ridge-like feature possibly resulting from differential flushing of fresh groundwater beneath a paleochannel. Movement of saltwater is being monitored in cooperation with the Accomack-Northampton Planning District Commission using well-logging techniques that detect small changes in groundwater salinity.