Estimated Water Use in Montana in 2000

By M.R. Cannon and Dave R. Johnson

U.S. Geological Survey
Scientific Investigations Report 2004-5223

In cooperation with Montana Department of Natural Resources and Conservation

Abstract

The future health and economic welfare of Montana's population is dependent on a continuing supply of fresh water. Montana's finite water resources are being stressed by increasing water withdrawals and instream-flow requirements. Various water managers in Montana need comprehensive, current, and detailed water-use data to quantify current stresses and estimate and plan for future water needs. This report summarizes selected water-use data for all of Montana's counties and stream basins to help meet those needs.

In 2000, the citizens of Montana withdrew and used about 10,749 million gallons per day (Mgal/d) of water from Montana's streams and aquifers. Withdrawals from surface water were about 10,477 Mgal/d and withdrawals from ground water were about 272 Mgal/d. Agricultural irrigation accounted for about 10,378 Mgal/d or about 96.5 percent of total withdrawals for all uses. Withdrawals for public supply were about 136 Mgal/d, self-supplied domestic withdrawals were about 23 Mgal/d, self-supplied industrial withdrawals were about 61 Mgal/d, withdrawals for thermoelectric power generation were about 110 Mgal/d, and withdrawals for livestock were about 41 Mgal/d. Total consumptive use of water in 2000 was about 2,370 Mgal/d, of which about 2,220 Mgal/d (93.6 percent) was for agricultural irrigation.

Instream uses of water included hydroelectric power generation and maintenance of instream flows for conservation of wildlife and aquatic life, and for public recreational purposes. In 2000, about 74,486 Mgal/d was used at hydroelectric plants for generation of about 11,591 gigawatt-hours of electricity. Evaporation from large water bodies, although not a classified water use, accounts for a large loss of water in some parts of the State. Net evaporation from Montana's 60 largest reservoirs and regulated lakes averaged about 891 Mgal/d.

Contents

Glossary
Abstract
Introduction
    Purpose and Scope
    Sources of Data
    Methods of Analysis
    Factors Affecting Water Availability and Use in Montana
    Previous Investigations
    Units of Water Measurement
Estimated Use of Water in 2000
     Water Withdrawals and Consumptive Use by Category
            Irrigation
            Public Supply
            Self-Supplied Domestic
            Self-Supplied Industrial
            Thermoelectric Power Generation
             Livestock
      Instream Water Use by Category
             Hydroelectric Power Generation
             Water Reserved for Instream Flow Purposes
Evaporation from Major Reservoirs and Regulated Lakes
Summary
References Cited
Appendix 1:  Water Withdrawals by Hydrologic Unit for Six Categories of Use

Figures

1-6. Maps showing:

1. Major river basins, counties, and selected towns in Montana.
2. Stream basins and Hydrologic Unit Codes.
3. Average annual precipitation in Montana, 1961-1990.
4. Average annual runoff in Montana, 1951-1980.
5. General extent of major aquifers in near-surface bedrock and semiconsolidated sediments in Montana.
6. General extent of unconsolidated deposits that yield water to shallow wells in Montana.

7. Graphs showing total water withdrawals in Montana by category and total water consumed in Montana by category in 2000.

8-14. Maps showing:

1. Total water withdrawals in Montana counties in 2000.
2. Total water withdrawals in Montana hydrologic units in 2000.
3. Irrigation water withdrawals in Montana counties in 2000.
4. Public-supply water withdrawals in Montana counties in 2000.
5. Self-supplied domestic water withdrawals in Montana counties in 2000.
6. Self-supplied industrial water withdrawals in Montana counties in 2000.
7. Livestock water withdrawals in Montana counties in 2000.

Tables

1. Runoff from Montana's rivers, 2000 calendar year and 1971-2000 average.
2. Common water-measurement units.
3. Total population and water withdrawals in Montana by county, 2000.
4. Total population and water withdrawals in Montana by hydrologic unit, 2000.
5. Irrigation water withdrawals and consumptive use in Montana by county, 2000.
6. Public-supply water withdrawals in Montana by county, 2000.
7. Self-supplied domestic water withdrawals in Montana by county, 2000.
8. Self-supplied industrial water withdrawals in Montana by county, 2000.
9. Water withdrawals for thermoelectric power generation in Montana by county, 2000.
10. Livestock water requirements.
11. Livestock water withdrawals in Montana by county, 2000.
12. Instream water use for hydroelectric power generation in Montana by county, 2000.
13. Montana streams with Murphy Rights instream-flow protection.
14. Estimated net reservoir evaporation for major reservoirs.

Appendix 1

1-1.  Irrigation water withdrawals and consumptive use in Montana by hydrologic unit, 2000.
1-2.  Public-supply water withdrawals in Montana by hydrologic unit, 2000.
1-3.  Self-supplied domestic water withdrawals in Montana by hydrologic unit, 2000.
1-4.  Self-supplied industrial water withdrawals in Montana by hydrologic unit, 2000.
1-5.  Water withdrawals for thermoelectric power generation by hydrologic unit, 2000.
1-6.  Livestock water withdrawals in Montana by hydrologic unit, 2000.

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