THE LIFETIME BEHAVIOR OF AN ARTESIAN GROUNDWATER SYSTEM: A MODEL FOR WATER SUPPLY PLANNING

The once abundant groundwater supply of the Virginia Coastal Plain is now threatened by overdraft. Accelerating rates of groundwater withdrawal and a long-term, persistent, and system-wide decline of artesian water levels warn of a coming crisis. In recognition of the problem, the Virginia legislature amended the Code of Virginia to require the development of a comprehensive water supply planning process, and the State Water Control Board has proposed expanding the current Eastern Virginia Ground Water Management Area to include the entire Virginia Coastal Plain. If planning and management of the groundwater supply is to be successful, then a clear understanding of the hydrologic functions and the lifetime behavior of the region's artesian aquifer system, from pre-development to socioeconomic maturity, is essential. The lifetime of a regional artesian groundwater system, such as that of the Virginia Coastal Plain, may be illustrated by a descriptive model composed of five interdependent elements: rate of groundwater withdrawal, groundwater supply (resource stock), artesian water levels, extraction and distribution costs, and scale of water supply planning and management. The model describes the tracks of these elements as they change with respect to time. Based on the behavior of the elements of the system, the lifetime of an artesian groundwater supply may be divided into five distinct eras: Era of Natural Equilibrium, Era of Abundance and Complacency, Era of Mounting Crises, Era of Supply Restructuring, and Era of Sustainability. These eras, while artificial, are not arbitrary; the boundaries between them are not hard and rigid lines but rather gradational zones in which some elements may overlap. This model provides a basic picture of the changes in the groundwater supply of the Virginia Coastal Plain during the decades ahead. Consequently, it can serve as a useful framework for water supply planning and management.