U.S. Geological Survey Groundwater Resources Program, 2001

Priorities for Regional Ground-Water Evaluations

Many ground-water systems extend across county, State, or other political boundaries. Despite this fact and the national importance of ground water, there is little ongoing assessment of ground-water resources availability at regional and national scales (National Research Council, 2000).

From 1978 to 1995, the U.S. Geological Survey (USGS) developed quantitative assessments of 25 of the Nation's most important regional aquifer systems, as part of the Regional Aquifer-System Analysis (RASA) Program. Most of the RASA assessments are 10 to 20 years old, and ground-water issues have increased in scope as competing demands on the resource have grown.

Concerns by Congress about declining efforts to evaluate the Nation's principal aquifers led to a 1998 USGS Report to Congress that outlines a strategy for addressing key regional issues about the Nation's aquifers, including the effects of lowered water levels and reductions in ground-water storage, saltwater intrusion, land subsidence, and reduced ground-water discharge to streams.

Following the Report to Congress, the National Research Council (NRC) conducted an evaluation of the Ground-Water Resources Program and, in November 2000, presented their findings in a report titled “Investigating Groundwater Systems on Regional and National Scales.” Based on the report to Congress and the NRC findings, the following seven scientific issues have been identified as high priority for the Ground-Water Resources Program.

1) Support for Aquifer Management Decisions—As pumping and other stresses placed on our ground-water resources intensify, new approaches being used to optimize ground-water extraction while limiting undesirable effects such as depletion of ground-water reserves, land subsidence, and harm to ecosystems. Innovations in artificial recharge, water reuse, and conjunctive use of ground-water and surface-water resources are leading to new challenges for USGS scientists to provide the data analyses, and predictive tools to support sound aquifer management decisions.

2) Natural Ground-Water Recharge—Information about the amount of water entering (recharging) the Nation's aquifers is vital, but the recharge rates are difficult to quantify. Improved knowledge of recharge processes, development and testing of new recharge estimation techniques, and methods to scale up specific site-recharge estimates to regional values are needed.

3) Ground-Water Flow in Shallow Aquifers—Ground water is pumped from shallow aquifers to supply water to homeowners with private wells, some municipalities, and agricultural users throughout much of the United States. These shallow aquifers are particularly vulnerable to contamination from human activities and sensitive to droughts and climate change.

4) Saltwater Intrusion—Ground-water pumping has caused saltwater intrusion in the majority of U.S. coastal States, as well as some inland areas. As coastal cities grow, this problem is likely to become increasingly important.

5) Ground-Water and Surface-Water Interaction—It is now recognized that nearly all surface-water features (streams, lakes, reservoirs, wetlands, and estuaries) interact with ground water. A fundamental understanding of these interactions is needed to evaluate their effects on water availability and the environment and to support watershed planning and management.

6) Ground Water in Karst and Fractured-Rock Aquifers—New methods are needed to help understand ground-water flow in karst and fractured-bedrock aquifers, which are the principal aquifers in many parts of the Nation. Many ground-water issues are amplified in fractured-rock aquifers because responses to pumping stresses and contamination can be more rapid than in aquifers where water flows through material such as sand and gravel.

7) Improved Hydrogeologic Frameworks—Ground-water movement is affected to a large degree by the properties of the rocks and soils through which the water flows. More maps that accurately show the geology in three-dimensions, as well as improved conceptual and statistical models of the geologic framework of aquifers, are needed to adequately assess ground- water resources and determine the effects of ground-water withdrawals.

New Models, Field Techniques, and Data for Ground-Water Evaluations

Enhanced Program Activities

	Hydrogeologic characterization of alluvial basins in the arid Southwest
	Assessment of ground-water and surface-water interaction related to irrigation in the Methow Valley, Washington
	Development and testing of new geophysical methods for monitoring saltwater intrusion and ground-water discharge to coastal bays in Massachusetts, Maryland, and Delaware
	Data collection and model development for saltwater intrusion in Virginia, North and South Carolina, Georgia, and Florida
	Fractured-rock aquifer analysis and related geologic mapping in Connecticut
	Studies of ground-water depletion and water use for the High Plains Aquifer in Wyoming, South Dakota, Colorado, Nebraska, Kansas, Oklahoma, Texas, and New Mexico
	Analysis of ground-water and surface-water interaction in Indiana and Michigan using new geologic maps from the Central Great Lakes Geologic Mapping Coalition
	Evaluation of the importance of microbiological processes related to regional ground-water-flow systems, especially for karst aquifers
	Overview of water issues for caves and springs in the Nation's parks
	Improved estimation of recharge rates in the humid eastern United States

References

National Research Council, 2000, Investigating groundwater systems on regional and national scales: Washington, D.C., National Academy Press, 143 p.

National Research Council, 2001, Future roles and opportunities for the U.S. Geological Survey: Washington, D.C., National Academy Press, 179 p.