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 past 25 years, overall water use has remained fairly stable according to a new U.S. Geological Survey report.

Assistant Secretary of the Interior Anne Castle announced the report, Estimated Use of Water in the United States in 2005, as part of her keynote speech on October 29 at the Atlantic Water Summit in the National Press Club.

The report shows that in 2005 Americans used 410 billion gallons 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 USGS began the series of five-year trend reports--along with the population that depends on these supplies.

"The importance of this type of data to the American public cannot be exaggerated," said Assistant Secretary for Water and Science Anne Castle. "The Department of the Interior provides the nation with the best source of information about national and regional trends in water withdrawals. This information is invaluable in ensuring future water supplies and finding new technologies and efficiencies to conserve water."

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," 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," Castle noted.

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 United States in 2005. More than half (53 percent) of the total withdrawals of 45,700 Mgal/d 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 United States 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 USGS 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.

Report: Estimated Use of Water in the United States in 2005

(ScienceDaily*, 16/11/2009)

*Adapted from materials provided by US Geological Survey.