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Estimated Use of Water in the United States in 1990
Introduction

head rule

dot Introduction
dot Purpose and Scope
dot Terminology
dot Sources of data and methods of analyses
dot Acknowledgments
dot Water use


- INTRODUCTION

Water management in the United States has traditionally focused on manipulating the country's abundant supplies of freshwater to meet the needs of users. This "supply management" approach has resulted in the building of large dams and conveyance systems, especially in the West. Increasing development costs, capital shortages, government fiscal restraint, diminishing sources of water supply, polluted water, and a growing concern for the environment have forced water managers and planners to begin to rethink traditional approaches to management and to experiment with new ones. Experts on the subject of water (supply and demand) in the western United States agree that the area is in transition from the era of water-supply development to an era of water-demand management and conservation, (Wilkinson, 1985). Quantitative assessments derived from the type of national compilation contained in this report can be used to evaluate the effectiveness of alternative water-management policies and conservation activities.

PURPOSE AND SCOPE

The purpose of this report is to present consistent and current water-use estimates by State and water-resources region for the United States, Puerto Rico, the U.S. Virgin Islands, and the District of Columbia. Estimates of water withdrawn from surface- and ground-water sources, estimates of consumptive use, and estimates of instream use and wastewater releases during 1990 are presented in this report. The U.S. Geological Survey 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). This series of reports can be used to develop and evaluate trends in water use and to plan for more effective uses of the Nation's water resources in the future.

This report discusses eight categories of offstream water use--- public supply, domestic, commercial, irrigation, livestock, industrial, mining, and thermoelectric power---and one category of instream use: hydroelectric power. Detailed information for other instream uses, such as navigation, recreation, pollution abatement, and fish habitat, is beyond the scope of this report. Information on wastewater-treatment facilities is given in the "Wastewater Release" section.

Information on many of the water-use categories in this report is more detailed than the information presented in previous water-use circulars in this series. For each category of offstream water use, 1990 withdrawal and consumptive-use estimates are discussed and those estimates are compared with corresponding 1985 estimates. The text is supplemented with illustrations and tables showing data for each State, Puerto Rico, the U.S. Virgin Islands, and the District of Columbia and for each of the 21 water-resources regions. (Water-resources regions are shown on a map on the inside of the front cover.) Totals are highlighted in the tables for ease of reference. At the beginning of this report is a section on total water use by category and source of water, and at the end is a section on trends in water use for the period 1950-90.

TERMINOLOGY

The terms and units used in this report are similar to those used in previous water-use circulars in this series. In this report, the term "offstream use" represents all water diverted or withdrawn from a surface- or ground-water source and conveyed to a place of use. "Instream use" refers to all uses taking place within the river channel itself. Hydroelectric power generation is discussed as an "instream use," although some hydroelectric power water uses could be considered as offstream use. The terms "freshwater, " "saline water," and "reclaimed wastewater," as types of water, are defined in the glossary. Saline water is reported only for the industrial, mining, and thermoelectric power categories. Some public supplies treat saline water before it is distributed, but all public-supply withdrawals are considered as freshwater in this report. Surface water and ground water, as sources of water, and the categories of water use also are defined in the glossary. In this report, withdrawals refer to self-supplied withdrawals, and deliveries refer to public-supply deliveries. "Consumptive use" refers to that part of the water withdrawn that is evaporated, transpired, incorporated into products and crops, consumed by humans or livestock, or otherwise removed from the immediate water supply.

SOURCES OF DATA AND METHODS OF ANALYSIS

In cooperation with State and local agencies, the water-use estimates for 1990 were compiled by the U.S. Geological Survey's District Offices for each county in the United States, Puerto Rico, and the U.S. Virgin Islands, and for 2,149 water-resources cataloging units. [For an explanation of cataloging units, see (Seaber and others (1987)]. These estimates were entered into a State water-use data base in each District Office and submitted to the Survey's headquarters in Reston, Va. The information was aggregated by State (including Puerto Rico, the U.S. Virgin Islands, and the District of Columbia) and by the 21 water-resources regions for each category of water use. All the water-use information compiled for this report is stored in the U.S. Geological Survey's Aggregate Water-Use Data System (AWUDS). Sources of information and accuracy of data vary and are discussed for each category in subsequent parts of this report.

More comprehensive analyses of field data and more detailed evaluations of existing water-use data were performed in the compilation of data for this report and for the 1985 water-use circular than for previous water-use circulars in this series. The increase in analyses and evaluations result from the U.S. Geological Survey's National Water-Use Information Program designed in 1978 to provide more uniform, current, and reliable information on water use. Documentation is available from each District Office that identifies the sources of water-use information for that State and describes how the water-use estimates were determined for this report. As the State water-use information programs are developed and refined, the timeliness and accuracy of water-use data at the State and national levels will continue to improve.

Two regional meetings were held during 1990 with U.S. Geological Survey and State water-use personnel to familiarize them with available sources of water-use information and preferred methodologies for data collection. Guidelines developed by the U.S. Geological Survey for preparation of State water-use estimates were distributed at those meetings. The following national data files were made available to each District for reference: U.S. Environmental Protection Agency Industrial Facilities Discharge files and Public Drinking Water Supply files, U.S. Bureau of Census population files, and the U.S. Department of Energy, Energy Information Administration reports. Each District was responsible for determining the most reliable source of information available for that State.

Water-use numerical data are the average daily quantities used. Irrigation water is applied during only a part of each year, and at variable rates; therefore, the actual rate of application is much greater than the average daily rate given in tables in this report. In this report, the numerical data generally are rounded to three significant figures for values greater than 100 and two significant figures for values less than 100. Most tables show these data in million gallons per day. Selected tables also show per-capita-use data in gallons per day, rounded to three significant figures, and irrigation and hydroelectric power data in thousand-acre feet per year. A conversion table is given after the glossary to assist those readers who may wish to convert the data to other units of measurement. All numbers were rounded independently; thus, the sums of individual rounded numbers may not equal the totals. The percentage changes discussed in the text, were calculated from the unrounded data.

Population data, which are from the U.S. Bureau of the Census population estimates and projections (U.S. Bureau of the Census, 1991), are shown to the nearest thousand. Data on population served by public supply were compiled in cooperation with State and local agencies; these data are rounded to three significant figures.

ACKNOWLEDGMENTS

The authors acknowledge the assistance provided by the many State and local agencies that cooperated with the U.S. Geological Survey, and the many U.S. Geological Survey water-use project chiefs that participated in the collection and compilation of data for this report. Many of the States publish reports on water use as part of their participation in the National Water-Use Information Program, and a selected list of these publications is given at the end of this report.

WATER USE

Water use in this report is subdivided into offstream use, instream use, and wastewater release. The difference among these types of use is explained below.

Offstream use is a water use that depends on water being diverted or withdrawn from a surface- or ground-water source and conveyed to the place of use. To determine the total quantity of water used (self-supplied withdrawals and public-supply deliveries), five subtypes of use are evaluated, as explained below and shown in the following sketch.

Sketch of the water-use cycle

1. Withdrawal---The quantity of water diverted or withdrawn from surface- or ground-water (A in sketch).
2. Delivery/release---The quantity of water delivered at the point of use (B) and the quantity released after use (C).
3. Conveyance loss---The quantity of water that is lost in transit, for example, from point of withdrawal to point of delivery (A-B), or from point of release to point of return (C-D).
4. Consumptive use---That part of water withdrawn that is evaporated, transpired, or incorporated into products or crops. In some instances, consumptive use will be the difference between the volume of water delivered and the volume released (B-C).
5. Return flow---The quantity of water that is discharged to a surface- or ground-water source (D) after release from the point of use and thus becomes available for further use.
In this report, self-supplied withdrawals, deliveries from public suppliers (where applicable), and consumptive use estimates are given for seven categories of offstream use: domestic, commercial, irrigation, livestock, industrial, mining, and thermoelectric power. For the public-supply category, in addition to withdrawals, the report also gives water delivered to domestic, commercial, industrial, and thermoelectric power users.

Each category of use typically has different effects on the reuse potential of return flows. Reuse potential reflects the quality and the quantity of water available for subsequent use; for example, irrigation return flow may be contaminated by pesticides and fertilizers, and, because of the high consumptive use of water during irrigation, the mineral content of the return flow often is substantially greater than that of the water applied. Consequently, irrigation return flow frequently has little reuse potential. This is a significant contrast to the reuse potential of most water discharged from thermoelectric plants, where the principal change in the water is an increase in temperature.

Instream use is a water use that takes place without the water being diverted or withdrawn from surface- or ground-water sources. Examples of instream uses are hydroelectric power generation, navigation, freshwater dilution of saline estuaries, maintenance of minimum streamflow to support fish habitat, and the assimilation of wastewater.

Quantitative estimates for most instream uses are difficult to compile on a national scale. However, because such uses compete with offstream uses and affect the quality and quantity of water resources for all uses, effective water-resources management requires that methods and procedures be devised to enable instream uses to be assessed quantitatively.

The only instream-use estimates compiled for this report are for hydroelectric power generation. Unlike other instream uses, the water used for hydroelectric power generation is a measurable quantity because the amount of water passed through the plant can be documented. Consumptive use in actual hydroelectric power generation (as opposed to evaporation from impoundments created by hydroelectric dams) generally is negligible.

In this report, wastewater release refers to water released from private and public wastewater-treatment facilities. Information is provided on the number of publicly- and privately-owned wastewater-treatment facilities and on releases from only the public wastewater-treatment facilities. The releases can be either returned to the natural environment or reclaimed for beneficial uses, such as irrigation of golf courses and parks.


USGS Water Use in the United States

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