Ground water is an important natural resource that provides water supply for coastal communities and freshwater discharge for coastal ecosystems. Aquifers along the Atlantic coastal zone of the United States, for example, are among the most productive in the United States, supplying drinking water to an estimated 30 million people from Maine to Florida. Saltwater intrusion caused by ground-water pumping, however, can contaminate coastal ground-water supplies and make ground water unfit for public consumption. Saltwater intrusion has been documented throughout the Atlantic coastal zone, but the degree and mechanisms of saltwater intrusion vary widely among localities and hydrogeologic settings. Moreover, coastal ecosystems are vulnerable to ground-water contamination caused by human activities, such as by nutrients and toxic compounds. Discharge of nutrient-contaminated ground water to coastal waters, for example, can trigger dense algal blooms that result in habitat changes and oxygen depletion, ultimately affecting the structure and function of coastal ecosystems.

During the past year, the U.S. Geological Survey Ground-Water Resources Program has begun to work collaboratively with other water-resource agencies and research programs to provide geoscience data and information to support ground-water-resource management decisions in the Atlantic coastal zone. The overall objectives of this work are (1) to collect data that will provide improved understanding of the hydrogeologic controls on coastal ground-water systems at local and regional scales and (2) to develop and apply new geophysical, geochemical, and numerical-modeling methods for analysis of subsurface freshwater-saltwater interactions. Current activities include development and testing of new geophysical methods for monitoring saltwater intrusion and ground-water discharge to coastal bays in Massachusetts, Maryland, and Delaware, and data collection and model development for saltwater intrusion in Virginia, North and South Carolina, Georgia, and Florida. This presentation will describe the objectives, scope, and recent findings of a few of these ongoing activities.