Arkansas Basin_Water Supply and Needs

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Section 5 Consumptive Water Needs in the Arkansas Basin -I pasture for domestic animals kept on the properties. Basin Roundtable feedback was mixed on whether new residential owners would tend to irrigate as diligently as the former rancher or farmer and whether overall water demands would change as a result of this new land use. Typical water use per acre for different types of M&lland use development in the South Platte Basin are shown in Figure 5-6. Generally, as residential densities increase, the gross water use per acre also tends to increase. Figure 5-6 shows that average gross water use can range from 1.3 AF/acre for industrial use to 3.5 AF/acre for higher density residential uses, such as apartments. Agricultural water deliveries and consumptive to historically irrigated lands vary widely and are dependent upon seniority of water rights, physical availability of supplies, timing of deliveries, delivery losses, and application efficiencies. The ability to use agricultural water rights existing on the land to meet the needs of M&I use as the land is developed is highly dependent upon these factors, plus the need for a portion of the water to be stored to meet non-irrigation M&I demands and to provide for firm yield for below average runoff years. These considerations are explained in greater detail in Section 8. 5.2 Estimated 2000 and Projected 2030 M&I and SSI Use Of the many factors affecting M&I water use, the projected increases in population clearly drive the increases in M&I use from 2000 to 2030. The effects of Level 1 conservation result in a projected reduction in per capita M&I water use of approximately 6 percent over this 30-year planning period. This reduction is reflected in the 2030 M&I water use projections presented in this section. M&I and SSI water use projections presented in this section represent the gross or total diversion amount, as opposed to the consumptively-used portion as described in Section 5.1.1.6. Single-Family Medium Density ~ o C) .s a:s (J ~ UJ :J "C ; Employment District ...J Single-Family Low Density To reiterate, M&I projections were developed by multiplying the estimated (2000) or projected (2030) populations Multi-Family Public Parks Commercial Industrial by per capita demands for each of the state's 64 counties, then reducing water use associated with Level 1 conservation measures for the 2030 scenario. These results were aggregated on a basin basis, as well as on a subbasin basis for use in the water supply "gap analysis" as presented in Section 8. Overall, combined M&I and 551 gross water use is expected to increase statewide by about 53 percent (630,000 AFY) over 2000 levels by 2030, as shown in Table 5-6. These projections do not include the impacts of water conservation efforts beyond Level 1 that are being implemented or planned by many M&I providers. These future conservation efforts are important strategies for meeting future water demands. The increase in M&I and SSI water use over this period by basin, and relative (percent) increase over 2000 M&I water use, are each presented in Figure 5-7. A summary of projected SSI water uses by type of industry and by county is provided in Table 5-7. Similar to the population patterns described earlier in this section, rates of M&I water use increases over the 30-year planning period are generally higher for the West Slope basins than for the Front Range. However, the bulk of the increase in water uses in terms of AFY will be in the South Platte and Arkansas Basins, which together represent about 80 percent of the total projected increase in Colorado's gross M&I and SSI demands. 3.5 2.2 1.9 2.0 1.4 1.6 1.3 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Annual Water Use in AF/acre Source: Cities of Westminster and Greeley and NCWCD CDIVI 5-8 Figure 5-6 Estimated Gross Urban Water Demands by Land Use (Indoor and Outdoor Use) o :\SHA WN\ARKANSAS\S5 _ARKANSAS. DOC