Water Resources of California
In 1950, the U.S. Geological Survey began publishing a series of water-use circulars entitled "Estimated Use of Water in the United States." Every 5 years since then the report has been updated and now provides a valuable, long-term data set of national water-use estimates. Since the inception of this series, California has always reported the largest total fresh and saline withdrawals of all states in the Nation (fig. 1). The most recent update in this series (Solley and others, 1998) reports 1995 conditions. California again accounts for the largest withdrawal of water for off-stream uses of all states, which is about 45.9 billion gallons per day, followed by Texas (29.6 Bgal/d), Illinois (19.9 Bgal/d), and Florida (18.2 Bgal/d, figs. 2 and 3).
The poster demonstrates WHY and HOW California continues to lead the Nation in many withdrawal categories (fig. 4 and 5). Withdrawals include water removed from the ground or diverted from a surface-water source for use.
WHY? California continues to be the most populous state in the United States, accounting for 12 percent of its people (more than 32 million in 1995) followed by Texas and New York with about 7 percent each (fig. 6). In 1995, California accounted for 5.62 Bgal/d, 14 percent of the Nation's public supply freshwater use (fig. 7). Public supply withdrawals are directly related to population supplied, but they also are influenced by withdrawals to supply industrial and commercial water users.
HOW? Los Angeles County's population exceeded 9.3 million in 1995 and contributed to the county's large public supply withdrawals. Only eight states have more people than Los Angeles County, which accounts for 29 percent of California's population (fig. 8).
WHY? California accounted for 28.9 Bgal/d in total irrigation withdrawals in 1995, with 22 percent of the Nation's total irrigation withdrawals (fig. 9).
HOW? The total withdrawals in the Tulare-Buena Vista Lake Hydrologic Cataloging Unit accounted for more than 8,330 Mgal/d in withdrawals for irrigation uses in 1995 (fig. 10) and 8,800 Mgal/d of total freshwater. Only 13 states had more total freshwater withdrawals. This area contains many of California's dairies and much of our irrigated acreage.
Even though California leads all states in total withdrawals, California's per-capita use rate for total off-stream use (1,130 gal/d) ranks below the national average (1,280 gal/d, fig. 11).
California Department of Food and Agriculture. Home Page. October 1998. http://www.cdfa.ca.gov/
Solley, W.B., Pierce, R.R., and Perlman, H.A., 1998, Estimated use of water in the United States in 1995: U.S. Geological Survey Circular 1200, 71 p. http://water.usgs.gov/public/watuse/
ACKNOWLEDGMENT
The author acknowledges the assistance of Michael B. Roque, Illustrator, in the layout and preparation of the original poster presented at the American Water Resources Association Annual Conference on Water Resources, November 16-19 1998, Point Clear, Alabama.
The author also acknowledges the assistance of Tammy Shelton, Management Analyst, in the development of the web page version of this information.
For more information you can contact William E. Templin at wtemplin@usgs.gov or 916-278-3177.