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<br />These spurious correlations within the sample data are a result of having <br />data from one point in time (i.e., the year 2000) and having only one data <br />point (i.e., total annual water use) per provider. Variation in per capita water <br />use in the current sample data is primarily a function of location. The data <br />issues could be resolved by obtaining monthly water use for each provider, <br />data by customer sector (such as residential, commercial, industrial), and <br />data for multiple years. Such data would provide variation in water use by <br />year, month, and sector characteristics. <br /> <br />Additional analysis of the sample data could be conducted if provider-level <br />water use and demographic data were available for a historical period. Such <br />time-series analysis may be able to separate factors that affect water use from <br />the locational differences in the data, and allow an analysis of the impact of <br />weather and demographic factors with respect to water use. <br /> <br />GPCD Results from Sample Database <br /> <br />The modeling results indicated that location was the dominant factor in <br />determining the variation of per capita water use among the sample data. <br />Thus, the average per capita water use per county was derived from the <br />sample data. Subsequent to the modeling effort described in the preceding <br />section, water use data for additional providers were obtained through <br />additional CDM survey responses and data from independent reports. Thus, <br />the sample size was increased to 255 providers. <br /> <br />The provider per capita values in each county were weighted by their <br />respective populations to produce a weighted average per capita value by <br />county. In addition, the weighted average per capita water use per basin was <br />also calculated. The sample data provided a per capita water use rate for 58 <br />of the 64 counties within the state. The average gallons per capita water use, <br />when weighted by population served, for the entire sample is 210.3 gpcd. <br />The county average per capita water use is shown in Table 7. The sample size <br />per county is also indicated, as well as the percent of county population <br />represented by the sample providers' population. The basin average per <br />capita is shown in bold text in Table 7 and is applied to counties without <br />sample data. Note that trans-basin counties are listed under multiple basins. <br /> <br />The county-level sample average per capita value is assumed to represent the <br />county per capita water use rate for most counties. The basin average per <br />capita rate is assumed for counties without representation in the sample <br />database. The assumed county gpcd water use rates shown in Table 7 are <br />multiplied by the county population projections (as shown in Appendix A) to <br />derive the estimated municipal and industrial (M&I) water forecast for each <br />county. These M&I forecasts are shown in Chapter IV. This estimation of <br />county per capita water use assumes that all residences, businesses and industries <br />throughout a county (including most self-supplied users) use water at the same rate <br />as the provider-supplied residences, businesses, and industries as represented in the <br />sample database. Where data were available regarding unique large self- <br />supplied water users in specific counties, these self-supplied water uses were <br />added to the county M&I water demand estimate, as described in the <br />following section. <br /> <br />III. Data Collection and Analysis <br /> <br />18 <br />