WASHINGTON, D.C. — The United States is using less water than during the peak years of 1975 and 1980, according to water use estimates for 2005. Despite a 30-percent population increase during the last 25 years, overall water use has remained fairly stable according to a new U.S. Geological Survey (U.S.G.S.) report.

The report shows that in 2005 Americans used 410 billion gallons of water per day, slightly less than in 2000. The declines are attributed to the increased use of more efficient irrigation systems and alternative technologies at power plants. Water withdrawals for public supply have increased steadily since 1950, when U.S.G.S. began the series of five-year trend reports, along with the population that depends on these supplies.

Nearly half (49 percent) of the 410 billion gallons per day used by Americans was for producing electricity at thermoelectric power plants. Irrigation accounted for 31 percent and public supply 11 percent of the total. The remaining 9 percent of the water was for self-supplied industrial, livestock, aquaculture, mining, and rural domestic uses.

“Because electricity generation and irrigation together accounted for a massive 80 percent of our water use in 2005, the improvements in efficiency and technology give us hope for the future,” Assistant Secretary for Water and Science Anne Castle said. “The report also underscores the importance of recognizing the limits of the drinking water supplies on which our growing population depends. While public-supply withdrawals have continued to increase overall, per capita use has decreased in many states during recent decades.

“These are just a few examples of why, if we want to understand and address the nation’s current water issues and prepare to answer future water questions, we need the data provided in this report.”

The series of reports provides information valuable to states and water suppliers because the water-use estimates are broken down by state, source, and category of water use. California, for example, is one of four states — joining Texas, Idaho, and Florida — that accounted for more than one-fourth of all fresh and saline water withdrawn in the U.S. in 2005. More than half (53 percent) of the total withdrawals of 45,700 million gallons per day in California were for irrigation, and 28 percent were for thermoelectric power.

The largest uses of fresh surface water were power generation and irrigation, and the states with the largest fresh surface-water uses were California, Texas, Idaho, and Illinois. The largest use of fresh groundwater was irrigation and the states with the largest fresh groundwater uses were California, Texas, Nebraska, and Arkansas.

The majority of irrigation withdrawals and irrigated acres are in the Western states, but significant increases in irrigation have occurred in some Southeastern states. Irrigation application rates have decreased steadily from 1950 to 2005. This decline is attributable to the increased use of more efficient irrigation systems.

The average amount of water withdrawn to produce a kilowatt-hour of electricity in the U.S. has decreased steadily from 1950 to 2005. This change is attributable to an increase in the number of power plants that use alternatives to once-through cooling.

Since 1950, the U.S.G.S. has compiled water use information by state in cooperation with state, local, and other federal agencies and organizations. The information reflects withdrawals from the nation’s rivers, streams, lakes, estuaries, and aquifers for major uses.

The full report is available at http://pubs.usgs.gov/circ/1344. Additional water use information is available at http://water.usgs.gov/watuse/.