MetroSouthPlatteInterimBasinWaterSupplyNeedsReport (2)

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Section 5 Consumptive Water Needs in the South Platte Basin and Denver/South Metro Counties IIIII Several sources of information were consulted in estimating per capita M&I water use. The CWCB's Drought and Water Supply Assessment study's database was used as an initial data source, and was supplemented in SWSI by sending a follow-up survey to more than 200 water providers. Including the responses to the follow-up survey, the resulting database used in SWSI includes nearly 250 water providers covering most of the state, as indicated in Figure 5-2. Regression analyses of available data indicated that location was the dominant factor in determining the variation of per capita water use among the sample data. ~.: '. ........ ... ~.4 .. .. .,:. .. .. &.t.. ..... . (\~.---' '. ~ ~ :..~.. .....~~............ ."..... .. .. .. - .. - Figure 5-2 Providers in SWS/ per Capita Demand Database The provider per capita values in each county were weighted by their respective populations to produce a weighted average per capita value by county. In addition, the weighted average per capita water use per basin was also calculated. The basin weighted average per capita rate was used for areas of the county that did not have representation in the sample database. The underlying assumption is that water use will be similar throughout the county. The estimated county gallons per capita per day (gpcd) water use rates were multiplied by the county population projections to derive the estimated M&I water forecast for each county. These M&I forecasts are shown in Section 5.2. population-weighted average per capita M&I water demand for the state was estimated to be 210 gpcd for the year 2000. This estimation of county per capita water use assumes that all residences, businesses, and industries throughout a county (including most self-supplied users) use water at the same rate as the provider-supplied residences, businesses, and industries as represented in the sample database. Where data were available regarding unique large self-supplied water users in specific counties, these self-supplied water uses were added to the county M&I water demand estimate, as described in the following section. Due to wide variations in the factors presented above, per capita use rates are difficult to directly compare between counties or basins. High per capita rates are not necessarily indicative of inefficient use, much as low rates do not necessarily imply efficient use. For example, water use related to tourism is reflected in historical demand data but not in census data, thus increasing the calculated per capita demands. Major industrial water uses supplied through municipal water systems could also drive per capita values upward. Residential or commercial properties such as golf courses might be irrigated from non-municipal sources, such as wells or ditch rights, lowering the calculated per capita demand. Changes in per capita rates might also be anticipated if a community's park system is essentially "built out" but population growth is still anticipated, or in cases where changes in industrial use do not directly correlate to changes in residential use. SWSI Basin Roundtable Arkansas Colorado Dolores/San Juan/San Miguel Gunnison North Platte Rio Grande South Platte (Total) Yampa/White 214[ 244 220 226 267 332 1206 230 The sample data provided a per capita water use rate for 58 of the 64 counties within the state. The aggregated basin average per capita water use estimates are depicted in Figure 5-3. Overall, the CONI 5-4 o 50 100 150 200 250 300 350 Average Per Capita M&I Water Use (gpcd) Figure 5-3 Estimated Year 2000 Average per Capita M&/ Water Use S:\1177\Basin Reports\South Platte\S5_South Platte.doc