Generally, water use is divided into two types: offstream
use (fig. 1) and instream
use. Offstream use involves the withdrawal
or diversion of water from a source, treatment, distribution, and use;
and the collection, treatment, and return flow of wastewater.
Instream use is water that is used, but not withdrawn, from a
surface- or ground-water source. The relations between the water-use
processes are illustrated in figure 2.
Figure 1. Water use flow diagram
Figure 2. Relations between water-use processes
Instream conveyance (fig. 1, E) occurs when water flows or is pumped from one reservoir to another without being used. Water may flow through a chain of reservoirs, from a river to a chain of lakes, from a river to a canal or aqueduct, or even from surface water to ground water. In some cases, the rate of water flowing or being pumped from one reservoir to another may be reported to a State regulatory agency and should be tagged as in instream use to avoid double or triple accounting of offstream withdrawals.
Quantitative estimates for most instream uses are difficult to compile. 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, definitions, and procedures be devised to assess instream uses quantitatively. The only instream use described in this report is for hydroelectric power generation. Unlike other instream uses, hydroelectric power generation water use is a measurable quantity because the amount of water passed through a power plant can be documented.
Although the need to have a minimum quantity of water in the streams has long been recognized as an important component of the stream ecosystem, it is only recently that the importance of instream flows have been acknowledged legally to the point where increases in instream flows have been mandated in many court and compact decisions throughout the country.
Methodologies and terms concerning instream flows currently (1995) have not been standardized. Previously, the need for standardization of nomenclature has been noted but not acted upon. Finally, the West Division, American Fisheries Society responded to this need for standardization and developed a Glossary of Stream Habitat Terms.
The approach for determining instream flow use and requirements are significantly different from offstream use and may be addressed in a subsequent chapter.
Areas with significant seasonal climatic variation may experience attenuated seasonal variation through restrictions or conservation programs that affect uses such as outdoor watering. Temporary restriction programs resulting from a drought can decrease water use markedly; however, when restrictions are not permanent, users tend to regress to previous water-use patterns. Some communities have permanent water-use restrictions, especially in arid States. Conservation programs, including retrofitting older buildings with low-flow fixtures, replacing grass with low water-use landscaping, and increasing prices for metered water users have a more permanent impact on water-use patterns. Restrictions on use, local ordinances, and conservation practices in an area need to be investigated before estimating use.
Water also can be reused as wastewater reclamation after release from a wastewater treatment plant. Decreasing availability of freshwater and increasing treatment costs tend to increase wastewater reclamation for irrigation or even commercial and industrial uses.
Choosing whether to use site-specific data or area estimates to estimate water use will depend on the objective of the water-use data collection; availability of statewide reported data; availability of time, manpower, and funds; and the area to be covered. The objective of the water-use data collection determines the required degree of accuracy and reliability and identifies individual data elements that are relevant. For example, if the objective of a water-use study is to compare the need for water by the textile industry with the need for water by the petroleum-refining industry in the United States, an estimate based on a coefficient per textile or petroleum-refining employee and the number of textile or petroleum-refining employees could be used. Similarly, if the objective is to determine withdrawals by people with their own wells for each county in a State, a coefficient of water use per person per day (per capita) could be used. However, if the objective is to determine industrial withdrawals within a small watershed, then either a complete inventory or a statistical sample of the industries would be required.
Area estimates are determined by using coefficients relating water use to another characteristic that is available for the area of interest, such as people per county or specific types of industry per state. Livestock water use almost always is estimated from published livestock surveys and established coefficients for water used by dairy cattle, beef cattle, sheep, pigs, and other livestock. Coefficients are most reliable when they are applied to uniform groups of users from which the coefficients were developed, such as livestock water use.
Applying coefficients to groups of users that are non-uniform, such as industries, must be approached cautiously. Water use by specific types of industries varies widely because of age and condition of the plants, processes used, the amount of recycled water used at each plant, and quality of the cooling water (James and others, 1980, p. 5). Any coefficients used for non-uniform users, however, can be improved locally through field verification of large facilities in the area of interest.
An inventory of all users, either by mail or site visit, is feasible if there are only a few users in the category of interest, such as thermoelectric facilities; available resources or time and manpower are relatively abundant; or the area to be covered is small. Even if an inventory of reported data is available, the accuracy of the data must be investigated.
The objective of statistical sampling is to collect information on a small but representative segment (sample) of a population and generalize the results to the total population. Statistical sampling methods are used to make an inference about groups of water users and their water-use characteristics on the basis of information obtained from a relatively small number of users. If done appropriately, the results of the sample can be used to develop a coefficient to apply to the population of users. Statistical sampling can decrease the cost of data collection and still maintain reliable estimates of water use. More accurate data collection from each site is feasible if fewer sites are sampled and time is spent collecting detailed water-use information on how the water is used rather than merely collecting data on the rate of withdrawal of use.
Stratified-random sampling is one form of sampling that offers considerable efficiency in water-use estimation and involves separating sites with similar water-use characteristics into groups or strata. Stratified-random sampling can increase the reliability of estimates on the basis of sample "means." The technique is used when there are known groups with particular water-use characteristics (for example, corn or tobacco growers, motels with swimming pools and restaurants, or golf courses). Stratification divides the population into internally similar groups. The greater the internal similarity of a group, the smaller the sample needed to adequately characterize water use for the group. Sampling a larger percentage of the major users than the minor users improves the reliability of the overall water-use estimates.
Selected statistical methods for estimating ground-water withdrawals were analyzed by Luckey. He determined that regression analysis and random sampling maintained an acceptable degree of accuracy and markedly decreased data collection. Statistical methods to estimate historical and 1980 irrigation requirements in the High Plains of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming were successfully applied by Heimes and Luckey (1982, 1983). Shoemyen (1979) presented a detailed description of the statistical sampling techniques used in the Suwannee River Water Management District.
Methods used to determine water use are the following: (1) collection
of data from the field (primary data acquisition); (2) compilation and
evaluation of measured or estimated data sent by water users to State
and Federal agencies (secondary data acquisition); or (3) derivation
of data through the use of coefficients, accounting methods, or models
(table 1). This section provides a basic description for using and
evaluating the reliability of each of these methods for all major
categories of water use.
Primary data collection should be preceded by a public-relations bulletin to inform the public about the purpose of the field inventory and the legal authority for conducting the survey. A public-relations bulletin will help to insure the cooperation of the landowners and farmers. The bulletin must explain the ultimate use of the data, and more importantly, how the participants will benefit.
Table 1. Methods used in determining site-specific water use
Sonic flowmeters may be the quickest and easiest method of determining instantaneous pipe flow. Portable sonic flowmeters can be attached to the outside of a pipe, calibrated, record the flow rate, and removed in usually less than an hour with no interference to the flow or the pumping operation. Several types and brands are available from various manufacturers. Flow rates may vary during the pumping period depending on drawdown in the well and possible system modifications; therefore, several measurements may be needed to determine an average flow rate over time.
The total volume of water use can be calculated by multiplying the instantaneous flow rate times the total time of operation for the period of interest. Fairly accurate values of running time may be available if an hour meter is located on the pumping equipment. An estimate of total flow can be calculated from the running time by recording the meter reading at the beginning and the end of the period of interest. If there are no timers on the existing equipment, a vibration time totalizer (VTT) can be installed on the pumping equipment. When placed on a vibrating pipe or pump, a VTT will sense the operation of the equipment and record the cumulative operating time (Shoemyen, 1979; Cordes, 1984). Electric pumps produce less vibration than nonelectric pumps, which may preclude the use of a VTT. However, an inductive time totalizer (ITT) can be installed on the electric wire supplying alternating current and provide the same information as the VTT (Cordes, 1984). Some users may keep an accurate log of operating times for the pump, which can be used to estimate total withdrawals.
Selection and use of meters are described by the U.S. Bureau of Reclamation, "Water Measurement Manual" (1974). In addition, the American Water Works Association (1986) describes the selection, installation, testing, and maintenance of water meters. However, the accuracy of the meter readings from older meters should be checked with another measurement method or a nonintrusive flowmeter, such as a sonic flowmeter (Arvin, 1992, Shoemyen, 1979; Cordes, 1984).
Important sources of reported data may be available from State allocation programs, Health Departments, and Pollution Control Agencies, as well as Federal agencies like the USGS and USEPA. Approximately 85 percent of the States have a permitting or registration program for those who withdraw water that is accompanied by either a request or requirement reporting withdrawals (Don Arvin, U.S. Geological Survey, written commun., 1993). The USGS compiles water-use data in support of a Congressional mandate to compliment the USGS data on the availability and quality of the Nation's water resources. USEPA requires major industrial users and wastewater-treatment facilities to report the volume of discharge to surface-water bodies at least annually. Records of metered water-use data also may be available from public water suppliers and wastewater-treatment facilities.
Surveys, particularly mail surveys, may provide timely and relatively inexpensive estimates of water use. However, selection of populations, collection of data, and tabulation of results need to be properly monitored to ensure reliability. Respondent cooperation and overall response can be greatly enhanced by site visits and telephone follow-ups, but the cost also increases with such visits and follow-ups.
Reported and surveyed water-use data must be used with caution because the accuracy and reliability of individual withdrawal or discharge reports varies considerably. Reported or surveyed water-use data may be either metered or estimated. Metered data generally are reliable; however, metered water-use values may be less accurate if the design flow of the meter is not within the actual flow through the meter, if the meter has not been calibrated lately, or if it is inexpertly read. Some users mistakenly report the actual reading from a cumulative meter, which would indicate an increased use each month. Further errors may occur during transfer of readings from the meter to the field sheet and to the data base. Reported or surveyed water-use data, which are based on estimates, require evaluation for the estimation method. In some cases, the reported water use may conform more closely with withdrawal and discharge permits rather than with actual use. Estimates of total water use depend on accurate reports, and an adequate number of returned questionnaires. Reported or surveyed water-use data are rarely field verified.
Models that use extrapolation techniques especially are appropriate for estimating total water use in situations where extreme accuracy and detail are not required. Extrapolating water-use values through time is based on the assumption that current water use can be determined by water-use trends in the past. Time is the independent variable and water use is the dependent variable. Models based on extrapolation include simple regression and trend analysis.
Non-econometric multiple-coefficient models consider water use as a mathematical function of two or more explanatory variables, related to such factors as weather or demographics and do not include price or economic factors. Water use is considered a necessary requirement unaffected by price. The variables are incorporated in a model that fits historical data and the coefficients are estimated statistically, usually by multiple regression.
Econometric models are based on economic factors and the demand for water is estimated as a function of the price of water and other economic factors. Multivariate demand models determine water-use demand as a function of weather, economics, and demographics, and the function is statistically determined. Econmetric models are especially appropriate for estimating total public water-supply water withdrawals and deliveries. One of the more frequently used models, the Corp of Engineer's Institute for Water Resources-Municipal and Industrial Needs Model (IWR-MAIN model) is described in Davis, and others, 1991.
Accounting models use a general equation that relates various water-use activities. In general, the volume of use is equal to the total volume of water received by the user (fig. 2). The volume of use also is equal to the sum of consumptive use plus the total volume of water released. If measured or estimated values are placed into the following equation (letters and numbers in parenthesis refer to Figures 1 and 2).
water use - consumptive use = wastewater collection (C2) + return flow (C3),
There are several different groups of water-use data; (1) identification, (2) geographic, (3) hydrologic, and (4) rate or volume. Identification data include the name, address and identification (ID) numbers that tie together different data sets by using the permit numbers or other unique numbers assigned to users by different data collectors. Geographic information are imperative when a Geographic Information System (GIS) is used. A latitude-longitude coordinate precisely locates the user or other point of interest and identifies the county, MCD, State, and watershed in which the user is located.
Hydrologic information identifies the resources affected, such as the river, watershed, or aquifer. Withdrawals from each principal aquifer in an area is often useful information. Data on withdrawal sites, such as drillers' well logs, may be available from the USGS ground-water files in State District offices. Information also may be available from State pollution control agencies or State public health agencies.
Water-use data can be collected in several different units. Volume measurements are usually combined with a time interval. Million gallons per day (Mgal/d) are frequently used in the East along with million gallons per year (Mgal/yr). Acre/feet per year are used more frequently in the West. Public water supply and wastewater-treatment facilities may also use average daily demand (ADD) and maximum daily demand (MDD) in million gallons per day. Meter readings are frequently in thousand gallons or 100 cubic feet. Water-use data are most often expressed as a rate of use: a volume over time. The objective of the water-use collection will determine the importance of the time interval. Water use can be expressed as an annual total in million gallons or acre-feet. More frequently, it is expressed as a daily rate. This daily rate represents the annual volume divided by 365 days, or a maximum daily rate during a shorter period of time, for instance, a summer month, or a peak daily rate.
Establishment of good water-use data bases does not need to be the responsibility of a single agency. Coordinating committees and working groups can work toward establishing statewide or basinwide computerized data bases. The data base can be developed, updated, and accessed by all agencies requiring the information. All updates can be coordinated through and certified by the coordinating committee.
Baker, N.T., 1988, Management techniques for site-specific water-use information in Symposium on Water Use data for Water Resources Management, Tucson, Ariz., 1988, Proceedings: American Water Resources Association, TPS-88-2, 872 p.
Horn, M.A., 1986, Development of a water-use data system in Minnesota: U.S. Geological Survey Water-Resources Investigations Report 85-4306, 59 p.
Horn, M.A., and Craft, P.A., 1991. Plan for developing a water-use data program in Rhode Island: U.S. Geological Survey Water Resources Investigations Report 90-4207, 26 p.
Juracek, K.E., 1992, Use of a geographic information system to assist in water-resources management and water-use studies--a prototype system for Kansas: U.S. Geological Survey Open-File Report 92-142, 14 p.
Khanal, N.N., 1980, A demonstration project on water use data collection storage and retrieval system: West Palm Beach, South Florida Water Management District, Technical Publication 80-2, 57 p.
Mathey, Sharon B. 1990, National water information system user's manual, v. 2, chapter 5, water use data system Part 1, Site Specific Water-use Data System (SSWUDS): Reston Va., U.S. Geological Survey Open-File Report 90-198, Version 90.2, variously paged.
Minnesota Land Management Information Center, 1984, State water-use data system (SWUDS) documentation: Minnesota Land Management Information Center, 43 p.
Perlman, H.A., 1992, Use of automated methods to prepare a U.S. Geological Survey publication on water in the United States in D.A. Wiltshire, ed, The applied computer sciences: U.S. Geological Survey Bulletin 2016, p. F1-F7.
Peters, K.R., and Members of the Virginia Water-Use Data System Task Force (eds.), 1981, Virginia water use data system pilot study area: Virginia State Water Control Board, 78 p.
Pierce, R.R., and Barber, N.L., 1982, Organizing Georgia's water-use data for effective management, in State, county, regional and municipal jurisdiction of ground-water protection, in National Ground-Water Quality Symposium, 6th, Atlanta, Georgia, September 22, 1982, Proceedings: Worthington, Ohio, National Water Well Association, p. 127-130.
Snavely, D.S., 1986, Water-use data-collection programs and regional data base of the Great Lakes-St. Lawrence River Basin states and provinces: U.S. Geological Survey Open-File Report 86-546, 206 p.
Templin, W.E., 1986, Water-use information for California: U.S. Geological Survey Open-File Report 86-483, 8 p.
-----1988, The California water-use geographic information system, in Symposium on Water-Use Data for Water-Resources Management, Tucson, Ariz., 1988, Proceedings: American Water Resources Association, TPS-88-2, p. 77-84.
West Virginia Geological and Economic Survey, 1980, West Virginia Water use data system: West Virginia Geological and Economic Survey, Pamphlet, 6 p.
Quality assurance is important for all data collection, compilation, analysis, and use of water-use data. Each of the previous sections on water-use determination in this chapter discuss the weakness of the different determination methods. Metered data must be reviewed in the context of the meter accuracy and reliability. Coefficients need to be calibrated to local conditions. Calibration doesn't always require the collection of site-specific data, but may be accomplished by using corroborative data, as well as statistical analysis of the range and standard deviation to identify outliers or inconsistent data. Edit programs can be written to check the reliability of automated data and identify any discrepancies from one year to the next.
11.B.6. General selected references
These general references are for general water use information.
Subsequent reference sections will provide references for specific
categories of use and will not duplicate references in this
American Water Works Association, 1986, Water meters--Selection, installation, testing and maintenance: Manual M6.
American Water Works Association and Water Environment Federation, 1994, Proceedings of the Water Reuse Symposium, Feb 27-March 2, 1994, Dallas, Tex.:, 845 p.
Anderson, K.E., 1966, Water well handbook (4th ed.): Water Well Drillers Association, Rolla, Mo., 281 p.
Arvin, Don, 1992, Feasibility of using portable, noninvasive pipe flowmeters and time totalizers for determining water use: U.S. Geological Survey Water-Resources Investigations Report 91-4110, 65 p.
Bayha, Keith, 1978, Instream flow methodologies for regional and national assessments, Instream Flow Information Paper: No. 7, Fort Collins, Colorado: U.S. Fish and Wildlife Service, Office of Biological Services, Western Energy and Land Use Team, Cooperative Instream Flow Service Group; FWS/OBS-78/61; 97 p.
Brown, T.C., Taylor, J.G., and Shelby, Bo, 1991, Assessing the direct effects of streamflow on recreation: A literature review: Water Resources Bulletin, American Water Resources Association Paper no. 91122.
Canadian Government Publishing Centre, 1986, Canada water year book, water use edition: Ottawa, Canadian Government Publishing Centre Supply and Services, 98 p.
Cordes, E.H., 1984, Ground water instrumentation program of the U.S. Geological Survey: Ground-Water Monitoring Review, v.4, no. 4, p.103-114.
Davis, W.Y., Rodrigo, D.M., Opitz, E.M., Dziegielewski, Benedykt, Baumann, D.D., and Boland, J.J., 1991, IWR-MAIN water use forecasting system, version 5.1--users manual and system description, consultant report:, Carbondale, Ill., U.S. Army Corps of Engineers and Planning and Management Consultants, 307 p.
Gleick, P.H., 1993, Water in crisis, A guide to the world's fresh water resources: New York, Oxford University Press, 473 p.
Heimes, F. J., and Luckey, R.R., 1980, Evaluating methods for determining water use in High Plains in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming, 1979: U.S. Geological Survey Water-Resources Investigations 80-111, 118 p.
-----1982, Methods for estimating historical irrigation requirements from ground water in the High Plains aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Water-Resources Investigations Report 82-40, 64 p.
-----1983, Estimating 1980 ground-water pumpage for irrigation on the High Plains in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Water-Resources Investigations Report 83-4123, 36 p.
Helm, W.T., ed., 1985, Glossary of stream habitat terms: Western Division, American Fisheries Society, 34 p.
Holland, T.W., 1992, Water-use data collection techniques in the Southeastern United States, Puerto Rico, and the U.S. Virgin Islands: U.S. Geological Survey Water-Resources Investigations Report 92-4028, 186 p
Holland, T.W., and Baker, N.T., 1993, Evaluation of pumpage data furnished by selected public water suppliers in Arkansas, May 1990 through March 1991: U.S. Geological Survey Water-Resources Investigations Report 93-4104, 80 p.
Horn, M.A., Craft, P.A., and Bratton, Lisa, 1994, Estimation of water withdrawal and distribution, water use, and wastewater collection and return flow in Cumberland, Rhode Island, 1988: U.S. Geological Survey Water-Resources Investigations Report 93-4023, 54p.
Hurr, R.T., and Litke, D.W., 1989, Estimating pumping time and ground-water withdrawals using energy-consumption data: U.S. Geological Survey Water-Resources Investigations Report 89-4107, 27 p.
International Great Lakes Diversions and Consumptive Uses Study Board, 1981, Great Lakes diversions and consumptive uses: Windsor, Ontario, Canada, International Joint Commission, 56 p.
International Joint Commission, 1985, Great Lakes diversions and consumptive uses: Windsor, Ontario, Canada, International Joint Commission, 82 p.
James, I.C., II, Kammerer, J.C., and Murray, C.R., 1980, How much water in a 12-ounce can? A perspectqive on water-use information: Pamphlet reprint from U.S. Geological Survey Annual Report, fiscal year 1976, 18 p.
Kammerer, J.C., 1982, Estimated demand of water for different purposes, in Water for human consumption, man and his environment: International Water Resources Association, Dublin, Tycooly International Publishing Limited, 606 p.
LaTour, J.K., 1991, Determination of water use in Rockford and Kankakee areas, Illinois: U.S. Geological Survey Water-Resources Investigations 90-4166, 79 p.
Luckey, R.R., 1972, Analyses of selected statistical methods for estimating ground-water withdrawal: Water Resources Research, v. 8, no. 1, p. 105-210.
Mather, J.R., 1984, Water Resources: Distribution, use, and management, John Wiley and Sons and W.H. Winston and Sons, Silver Spring, Md., 439 p.
National Water Use Information Program, 1994, A supplementary guide to using the IWR-MAIN water use forecasting system with special case study. Emphasis on the MWD-MAIN version: University of Wyoming in cooperation with the U.S. Geological Survey.
Schefter, J.E., Moody, D.W., 1981, Water use data--who needs it: Water Resources Bulletin, v. 17, no 6, 978 p.
Shoemyen, J.L. (ed.), 1979, Procedure for assessing agricultural water use: Suwannee River Water Management District, Department of Planning and Operations, 114 p.
Solley, W.B., Pierce, R.R., and Perlman, H.A., 1993, Estimated use of water in the United States in 1990: U.S. Geological Survey Circular 1081, 76 p.
Sudman, Seymour, 1976: Applied sampling: New York, Academic Press, Incorporated, 249 p.
Sweat, M.J., Van Til, R.L., 1988, Water use and methods of data acquisition in Michigan, in Symposium on Water-Use Data for Water-Resources Management, Tucson, Ariz., 1988, Proceedings: American Water Resources Association, TPS-88-2, p. 872.
Tate, D.M., 1990, Water demand management in Canada--a state-of-the-art review: Environment Canada, Social Science Series no. 23, 52 p.
U.S. Bureau of Reclamation, 1974, Water measurement manual: Denver, Co., U.S. Bureau of Reclamation, 327 p.
U.S. Department of Agriculture, 1989, the Second RCA appraisal: Soil, water, and related resources on nonfederal land in the United States; Analysis of Condition and Trends: 280 p.
U.S. Environmental Protection Agency, 1993, Guide to Federal water quality programs and information: Washington D.C., EPA-230-B-93-001, 194 p.
U.S. Office of Management and Budget, 1987, Standard industrial classification manual, 1987: U.S. Government Printing Office, 705 p.
Van Der Leeden, Frits, Troise, F.L., and Todd, D.K. (eds.), 1990, The water encyclopedia (2d ed.): Chelsea, Mich., Lewis Publishers, 808 p.
Wilson, B.C., 1992, Water use by categories in New Mexico counties and river basins, and irrigated acreage in 1990: New Mexico State Engineer Office, Technical Report 47, 141 p.