NEAR-SURFACE AQUIFER DEVELOPMENT, NITROGEN SATURATION, AND THEIS CAPTURE: LESSONS FROM LIZZIE

Ground-water development of North Carolina’s coastal aquifer systems has upset a long-term equilibrium condition between aquifer recharge, and discharge to streams, rivers, and other water bodies. Increasing overdrafts in the deeper Cretaceous aquifers has led the state to impose restrictions on withdrawals from these aquifers. These restrictions are forcing ground-water users to consider development of overlying aquifers nearer to land surface. Development of these near-surface aquifers, however, raises serious conjunctive use and sustainability issues. North Carolina has twin goals of sustaining Coastal Plain water supplies and preserving healthy rivers and estuaries. As aquifer development migrates to near-surface aquifers, conflict between these goals can be expected to increase.

In this presentation we apply the basic hydrodynamics of aquifer recharge and discharge developed by C. V. Theis to illustrate the potential impacts of near-surface aquifer development on stream health. Stream health is characterized in terms of wetlands preservation, nitrate concentration, and the state’s goal of reducing nitrogen loading by 30 percent. To link aquifer development and stream health, we introduce the notion of nitrogen saturation and its potential implication for coastal aquifer systems. These surface water-ground water interactions are illustrated by example using the Lizzie intensive study site in Greene County, NC, developed collaboratively by state and federal agencies and local landowners. An accompanying poster presents development of a geologic framework at Lizzie that forms the foundation for the hydrogeologic analysis of the site. This research suggests that the state may benefit from a more holistic approach in management of its coastal aquifer systems and interconnected stream network.