Estimating Water Use in the United States A New Paradigm for the National Water-Use Information Program (2002) / Chapter Skim
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4. Overview of Water Use Estimation
4. Overview of Water Use Estimation
Pages 68-85
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From page 68... ...
The diverse goals of water use estimation, and the varied categories and methods used to estimate water use, suggest no single approach can be or should be expected to satisfy all the requirements of the National Water-Use Information Program (NWUIP)
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From page 69... ...
The following section contrasts strengths and limitations of alternative methods for estimating water use. DIRECT ESTIMATION Direct estimation methods can be broadly divided into the complete inventory approach and the stratified random sampling approach.
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From page 70... ...
Indeed, the ambiguity in the purpose and goals of this data collection effort is evidenced by the evolution and redefinition of water use categories and data collections methods and even by the redefinition of water use in each of the Survey's pentannual water use assessments. Nevertheless, the USGS water use categories provide an internally consistent data structure to formulate and organize water use estimates within each state.
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From page 71... ...
When a complete inventory is impractical, water use may be estimated directly using formal sampling techniques, such as those described in Chapter 5. Stratified Random Sampling The enormous variation in both the quality of available water use data and the economic and climatic patterns of water use among the states poses substan
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From page 72... ...
Viewing the Census of Agriculture as a model for nationally consistent county-level stratified random sampling highlights a number of significant features and methodological issues that would be common to the national estimation of water use: · The sample design rigorously emphasizes computing the standard error, and hence confidence limits, on all estimates. · The program fosters an institutional culture of continuous improvement in sequential estimates.
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From page 73... ...
The following are required for indirect estimation: activity-based water requirements and water use coefficients, correlation-based models estimated with regression techniques, econometric models of water use behavior, materials flow models estimated from macroeconomic national accounts data, system-level models that explicitly optimize water use decision-making, and indirect methods for consumptive use. Coefficient-Based Methods Coefficient methods or unit use coefficient methods (including the wellknown per capita methods)
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From page 74... ...
74 ESTIMATING WATER USE IN THE UNITED STATES The simple example in Box 4.2 shows how analyzing the properties and error characteristics of water use estimators can help structure hypothesis-driven water use science that can be tested in USGS district water use programs. This science improves our understanding of water use, with immediate returns in improved techniques for water use estimation and uncertainty analysis.
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From page 75... ...
OVERVIEW OF WATER USE ESTIMATION 75 Multivariate Regression Multivariate regression methods, such as those described in Chapter 6, systematically utilize the correlation structure of observed water use and explanatory variables under the familiar assumptions of the standard linear model. For example, the regression of crop yields on evapotranspiration is widely used in
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From page 76... ...
For example, most of the observed variability in municipal water use can be explained by exogenous variables representing population and meteorology. Ancillary explanatory variables such as disaggregated data on housing price, per capita income, lot size, and water rates can further explain the variance in observed water use, when such data are available.
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From page 77... ...
The most parsimonious model for Northern Virginia water use explained increases above the mean seasonal water use by the number of consecutive antecedent dry days. In contrast, during the dry season in Los Angeles, mean seasonal water use is insensitive to the number of antecedent dry days, but unusually cool or wet weather can decrease municipal water use from the seasonal mean.
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From page 78... ...
In contrast, water requirement or empirical regression models implicitly treat water as a fixed technical requirement. The contrast between regression and econometric approaches to water use estimation can be highlighted by considering the choice of explanatory variables used to estimate municipal water use.
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From page 79... ...
Of perhaps greater value is the potential use of these data to identify significant structural changes and trends in regional economic activity that will require additional scrutiny and investigation to accurately update regional water use estimates. As a consistent indicator of county-level economic activity, BEA's regional economic data may be an efficient starting point in the sampling and design of each cycle of national water use estimation.
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From page 81... ...
For example, the pattern and structure of "employee water use" coefficients among the states could be systematically investigated through a series of state-level studies coordinated through the NWUIP, accounting for regional differences in climate and economic trends. The result of these investigations would feed back to the water use program in the form of improved procedures and quantitative uncertainty analysis for national estimation of employee water use with coefficient methods.
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From page 82... ...
The approach combines National Accounts Data from I-O tables with available materials requirements by industry. The result integrates industry requirements and macroeconomic feedbacks to estimate the total material flow embodied in the final production of each sector of the economy.
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From page 83... ...
Augmented Income and Product Accounts The existing system of National Income and Product Accounts, along with National Accounts Data and Regional Accounts Data maintained by the BEA, can be an extremely useful source of nationally consistent, county-level data on industry-disaggregated economic activity. The convention that counts only market transactions yields an incomplete representation of national economic activity.
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From page 84... ...
As well, the USGS water use program is a unique source of national data on the nonmarket activities derived from the nation's water resources as they flow through both the economy and the hydrologic system. There is great potential for cooperation and coordination between the NWUIP and the BEA, galvanized by the mutual interest in "promoting better monitoring, assessment, and policy making" for the nation.
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From page 85... ...
CONCLUSIONS AND RECOMMENDATIONS Compiling a complete inventory of all water use in the United States is intuitively appealing, but impractical. This chapter provides an overview of the diverse methods available to estimate water use when direct measurements and observations are unavailable.
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