HYDROGEOLOGIC SCIENCE TO SUPPORT LONG-TERM AQUIFER MANAGEMENT: THE CASE OF THE VIRGINIA COASTAL PLAIN AQUIFER SYSTEM

Groundwater is an important water supply in the Virginia Coastal Plain, providing an estimated 1.1 million people with potable water in 2005. As groundwater withdrawals increased over the 20^th century, particularly from the 1950s on, water levels in the confined aquifers declined sharply and now are below sea-level over most of the coastal plain. With growing awareness of the water-level declines in the Virginia Coastal Plain aquifer system, hydrogeologists’ science priorities are moving from basic characterization towards assessment of aquifer sustainability and long-term risk and resource management.

Regulation of groundwater withdrawals by the state started in the late 1970s and grew along with use of groundwater and improved understanding of the aquifer system. Hydrogeologists have advised Virginia’s regulators in the development of state groundwater regulations and developed aquifer management tools. Data, hydrogeologic conceptual models, and numerical simulation models provide the foundation for understanding the aquifer system and for answering questions about current and future groundwater availability. Milestones in hydrogeologic understanding of the Virginia Coastal Plain aquifer system have included: discovery of the Chesapeake Bay impact crater, completion of a numerically detailed hydrogeologic spatial model, and completion of a correspondingly detailed numerical groundwater simulation model. Possible future hydrogeologic efforts may include adding land subsidence, detailed saltwater transport, and conjunctive use and optimization to the numerical groundwater simulation model and development of a regional groundwater simulation model to simulate groundwater flow across multiple state boundaries. A recent effort by the state to incorporate the most up-to-date hydrogeologic science into the regulatory program will be presented from a hydrogeologist’s viewpoint.