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Estimated Use of Water in the United States in 2000
Introduction
This report, "Estimated use of water in the United States in 2000", marks 50 years of water-use data compiled by the U.S. Geological Survey (USGS). Data on water withdrawals by State, source of water, and category of use have been compiled at 5-year intervals since 1950. Data from this Circular and other USGS water-use Circulars can be used along with information on the availability of ground water and surface water to assess water-resource management needs in the face of changing demands for water. Reliable water-use data are essential to many organizations and individuals in support of research and policy decisions.
Since 1950, water supplies and their uses have been affected by population growth, economic trends, legal decisions, and periodic droughts. In response to constraints on water supplies, communities have expanded their water-supply infrastructures or instituted water-conservation measures, farmers have changed crops or agricultural practices, and industries have reused or reclaimed process water. Population changes affecting water use during the time period from 1950 to 2000 include an overall growth of 90 percent, with a shift in the population of the United States from rural areas to urban areas and a continuing shift of the mean geographic center of population west and south (Hobbs and Stoops, 2002). In some geographic areas, the availability of water and improved technology have resulted in increases in irrigated acreage and irrigation water use. In other areas, increased costs and reduced water availability have led to more efficient irrigation practices and a reduction in irrigation water use. Changes in production, technology, and economic conditions have affected industrial water use. Periodic droughts have drawn attention to limits in the reliability of local and regional water supplies and influenced short-term water use for all users.
Climatic fluctuations affect water withdrawals, particularly for irrigation, power generation, public supply, and self-supplied domestic water use. However, effects of extremes in temperature and precipitation often are difficult to isolate from other factors that affect water use; thus, climatic effects cannot be identified readily based on the aggregated data contained in this report.
The year 2000 was one of climatic extremes. Weather in the Midwest and Northeast was characterized by prolonged periods of cooler and wetter than normal conditions. During the summer months (June-August), precipitation was above average in 15 States throughout this region. The South and West experienced severe drought as a result of below-normal precipitation and above-normal temperatures. Alabama, Florida, Georgia, Louisiana, and Mississippi had the driest May-October period on record during 2000. Streams and reservoirs dropped to record low levels, and some cities imposed drought restrictions. The driest July-September period was recorded in Arkansas, Kansas, Louisiana, Mississippi, Oklahoma, and Texas. Much of the western United States also was in severe drought-including Arizona, Colorado, Idaho, Montana, New Mexico, Utah, and Wyoming. By August 2000, 36 percent of the United States was in severe to extreme drought, leading to widespread wildfires and other drought-related damages (National Oceanic and Atmospheric Administration, 2001; U.S. Department of Agriculture, 2000).
This report presents consistent and current water-use estimates by source and by State for the States, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands (referred to in the text as States or United States for brevity). The USGS has compiled similar national estimates every 5 years since 1950 (MacKichan, 1951, 1957; MacKichan and Kammerer, 1961; Murray, 1968; Murray and Reeves, 1972, 1977; and Solley and others, 1983, 1988, 1993, 1998). This series of water-use reports serves as one of the few sources of information about regional or national trends in water withdrawals. The report provides information on eight categories of water use—public supply, domestic, irrigation, livestock, aquaculture, industrial, mining, and thermoelectric power. This report contains a section on total water use for 2000, followed by more detailed discussions for each category. The final section presents a discussion on trends in water use from 1950 to 2000.
The terms and units used in this report are similar to those used in previous USGS water-use Circulars and are defined in the Glossary . For 2000, water use was defined as water withdrawals rather than as water withdrawals plus deliveries from public supplies. Saline water, defined as water that contains 1,000 milligrams per liter or more of dissolved solids, was tabulated for the industrial, mining, and thermoelectric-power categories. All public-supply, self-supplied domestic, irrigation, and livestock withdrawals were considered freshwater in this report. For aquaculture, only freshwater withdrawals were reported for 2000.
Annual water-use data are expressed in terms of million gallons per day (abbreviated as Mgal/d)
and thousand acre-feet per year in this report. The term billion gallons per day (one-thousand million
gallons per day, abbreviated as Bgal/d) is used in the Abstract and Trends sections of this report to
more simply express large numbers. Units of million gallons per day or billion gallons per day are used to
indicate an average daily rate of usage, and do not represent actual daily rates. For example, irrigation
water is applied only part of each year and at variable rates; therefore, the actual rate of application
at any given time during the growing season would be more than the average daily rate expressed as
million gallons per day or as billion gallons per day.
The water-use data in this report are rounded to three significant figures. All values are rounded independently; therefore, the sums of individual rounded numbers may not equal the totals. The percentage changes discussed in the text are calculated from the unrounded data and expressed as integers. All population data are rounded to three significant figures.
The number of reported categories and the data elements collected were reduced for 2000, and some States collected data for only certain core categories. Emphasis was placed on ensuring the quality of data that were collected, rather than attempting to provide all categories and data elements on a national scale. Additional water-use data were collected for some States as part of a broader water-use data-collection program.For 2000, self-supplied water withdrawals for the core categories of public supply, domestic, irrigation, industrial, and thermoelectric power were compiled for all States. Self-supplied water withdrawals for livestock, aquaculture, and mining were compiled for selected States that represented most of the total water withdrawals for these categories during 1995. Data not reported for 2000 included self-supplied commercial withdrawals, deliveries from public supply for domestic, commercial, industrial, and thermoelectric-power purposes, and instream use for hydroelectric power. Also not reported were consumptive use, irrigation conveyance loss, reclaimed wastewater, number of wastewater facilities, and wastewater returns. The amount of power generated by thermoelectric- or hydroelectric-power plants was not reported for 2000.
Although some States did not compile data for some categories for 2000, most of the water withdrawals are likely to be accounted for in the water-use estimates in this report. During 1995, 97 percent of total water withdrawals were used for public supply, domestic, irrigation, industrial, and thermoelectric power. All States collected and reported data for these categories for 2000. The remaining 3 percent was used for livestock, animal specialties, mining, and commercial purposes. States that accounted for the majority of the water withdrawals for livestock, aquaculture, and mining uses for 1995 collected and reported data for 2000.
Other changes for 2000 involved the reclassification of data within the thermoelectric-power and livestock categories. Thermoelectric-power water use was subdivided by cooling type (once-through or closed-loop) rather than by fuel type as in previous reports. Cooling-system type is the primary determinant of consumptive use relative to withdrawals at power plants. Most of the water withdrawn for once-through cooling is returned to the source and, therefore, generally results in a relatively smaller consumptive use. Water withdrawn for closed-loop cooling is recirculated with a large part lost to evaporation, resulting in a larger consumptive use relative to withdrawals.
For 2000, the livestock category was no longer subdivided into livestock and animal specialties. Withdrawals for some animals that formerly were reported in the animal-specialties subcategory were included in the livestock category. The aquaculture category, new for 2000, combined withdrawals for fish farms, formerly reported in the animal-specialties category, and fish hatcheries, formerly reported as self-supplied withdrawals in the commercial category.
Sources of Data and Methods of Analysis
The USGS, in cooperation with State and local agencies, compiled water-use estimates for 2000 for each county in the United States, the District of Columbia, Puerto Rico, and the U.S. Virgin Islands. The USGS National Water Use Information Program—implemented in 1978 to provide uniform, current, and reliable information on water use—coordinated the compilation effort. Water-use estimates and ancillary data were entered into a State aggregate water-use database in each USGS State office, and reviewed within the USGS and cooperating agencies. All water-use data compiled for this report are stored in the USGS Aggregate Water-Use Data System. Data collected for this report are available by county and State on the Internet at http://water.usgs.gov/watuse/.
Sources of information vary and are discussed for each category in subsequent parts of this report. Guidelines for preparing USGS water-use estimates for 2000 were developed and distributed to water-use study chiefs in each State office, and are available on the Internet. The following national data were available to each State: U.S. Environmental Protection Agency (USEPA) Safe Drinking Water Information System (SDWIS); U.S. Census Bureau, population; U.S. Department of Agriculture (USDA) Farm and Ranch Irrigation Survey; USDA Census of Agriculture; USDA, national agricultural statistics; and U.S. Department of Energy-Energy Information Administration (USDOE-EIA), steam-electric plant statistics. Each USGS study chief was responsible for determining the most reliable sources of information available for estimating water use for their State.
Each USGS study chief compiled and analyzed information from various sources, made estimates of missing data, and prepared documentation that identified the sources of water-use information and methods used to determine water use for their State. Many States published reports on water use as part of the National Water Use Information Program. A list of these publications is available on the Internet.
The authors gratefully acknowledge the USGS study chiefs in each State who compiled the data for this report and the assistance provided by the many State and local agencies that shared data and expertise with the USGS. In many States, personnel from cooperating agencies worked as full partners with the USGS in this compilation effort. Cooperators include State agencies that manage water resources, operate data-collection programs, and administer regulations on water use and natural resources. The USGS water-use points of contact for each State are identified on the Internet.
Water Use in the United States | USGS Water Resources of the United States
For more information: wu-info@usgs.gov