Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

The Indicator

The Data

Data Source: Using raw data collected by states and other sources, the U.S. Geological Survey (USGS) compiles estimates of water use for each use category and then aggregates the estimates for each state, Puerto Rico, and the U.S. Virgin Islands and for each of the 21 water-resources regions. The data have been published every 5 years since 1950 in the USGS Circular series Estimated Use of Water in the United States. More recent compilations are available electronically at http://water.usgs.gov/watuse/. Some state and federal agencies also publish reports on water use for specific states or categories of use.

Data Collection Methodology: Sources of information and accuracy of data vary by state and by water-use category. Most public-supply water withdrawals and deliveries are metered. In some states, large irrigation and industrial users are required to have water meters to measure the amount of water withdrawn. For other categories, such as self-supplied domestic (e.g., “rural”) and small industries (e.g., self-supplied commercial), estimates of water use are derived from population or product output. Energy production data obtained from the Department of Energy are used in making water-use estimates for the thermoelectric power category. Information on acres irrigated is obtained from the Department of Agriculture’s Census of Agriculture and its Farm and Ranch Irrigation Survey and from state universities. Information on public water supplies is obtained from the Environmental Protection Agency, state agencies, and individual water suppliers.

Data Manipulation: The steps required to transform the raw data into final form vary with the category of use and with the level of detail of the available raw data. Guidelines used for preparing the most recent estimates are available at http://water.usgs.gov/watuse/. In addition, sources of information and accuracy of data are discussed in the USGS circulars published every 5 years.

Data Quality/Caveats: Because the sources of data and the level of detailed information vary for each state, it is difficult to apply an error analysis to the national aggregate water-use estimates. As part of the compilation effort, each USGS compiler is required to provide justification when estimates change by more than 10% from the previous water-use compilation. Once the data are compiled at the state level, they are peer-reviewed by USGS regional water-use specialists and again by USGS national water-use specialists.

Data Access: The data used here are available in the regular USGS Circular series Estimated Use of Water in the United States (for historical data) and at http://water.usgs.gov/watuse/ (for more recent data).

2005 Web Site Update : Data for 2000 were obtained from the USGS web site as listed under Data Access.

The USGS discontinued monitoring of “self-supplied commercial” water withdrawals—previously combined with industrial and mining withdrawals in this indicator’s “industrial” category—in the 2000 Estimated Use of Water in the United States. Ideally, “commercial” withdrawals would have been removed from the “industrial” category for all years. However, “commercial” data could not be excluded from the entire dataset, because separate totals for the “commercial” freshwater withdrawal component of the “industrial” category were not available for the years 1960-1980. Note also, 2000 data exclude “livestock” withdrawals that were not reported for 29 states.