USGS Circular 1323

Ground-Water Resources Program

Ground-Water Availability in the United States

By Thomas E. Reilly, Kevin F. Dennehy, William M. Alley, and William L. Cunningham

U.S. Geological Survey Circular 1323, 70 pages (Published July 2008)

This report is available online in PDF format: Circular 1323 (Opens the PDF file in a new window. ) (19.4 MB)

Cover thumbnailGround water is among the Nation's most important natural resources. It provides half our drinking water and is essential to the vitality of agriculture and industry, as well as to the health of rivers, wetlands, and estuaries throughout the country. Large-scale development of ground-water resources with accompanying declines in ground-water levels and other effects of pumping has led to concerns about the future availability of ground water to meet domestic, agricultural, industrial, and environmental needs. The challenges in determining ground-water availability are many. This report examines what is known about the Nation's ground-water availability and outlines a program of study by the U.S. Geological Survey Ground-Water Resources Program to improve our understanding of ground-water availability in major aquifers across the Nation. The approach is designed to provide useful regional information for State and local agencies who manage ground-water resources, while providing the building blocks for a national assessment. The report is written for a wide audience interested or involved in the management, protection, and sustainable use of the Nation's water resources.



Challenges in Determining Ground-Water Availability

Ground Water—The Hidden Resource

Time Scales of Ground-Water Systems

What Do We Know About Ground-Water Availability in the United States?

Location and Description of Major Aquifers

Water Use

Changes in Ground-Water Levels and Ground-Water Storage


Ground-Water Discharge

Ground-Water Quality

Regional-Scale Approach to National Assessment

Regional Ground-Water Budgets

Selection of Regional Ground-Water Flow Systems

Regional Studies

Examples of Regional Aquifer Assessments

Middle Rio Grande Basin

California Central Valley Aquifer System

Coastal Plain Aquifer System

Great Lakes Basin

High Plains Aquifer

Future Directions


Selected References

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Suggested citation: Reilly, T.E., Dennehy, K.F., Alley, W.M., and Cunningham, W.L., 2008, Ground-Water Availability in the United States: U.S. Geological Survey Circular 1323, 70 p., also available online at

For more information, please contact Thomas E. Reilly.

This report is also available in print from:
USGS Information Services
Box25286, Federal Center
Denver, CO 80225
telephone: 888 ASK-USGS; e-mail:
Product Number: 208479 at the USGS Store
ISBN: 978-1-4113-2183-0

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