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<br />municipal, industrial and rural domestic; thermal electric
<br />power; livestock; and mineral. Generally, the future
<br />gross water requirements within the subbasins were
<br />based on projections of population and other economic
<br />parameters applicable to the uses cited. Table 20
<br />illustrates the overall magnitude of the gross water
<br />
<br />required, but these values do not reflect adequacy of
<br />supply, location, consumptive use, and water returned to
<br />the streams for further use and re-use. Establishment of
<br />net demands, therefore, required not only a stream
<br />analysis, but also plan formulation criteria which took
<br />into account the factors mentioned.
<br />
<br />Table 20 - WATER WITHDRAWALS REOUIRED FOR SELECTED USES BY 2020
<br />
<br />Subbasin
<br />
<br />M&I, Mineral, and
<br />Rural Domestic
<br />
<br />Total
<br />
<br />Upper Missouri
<br />Yellowstone
<br />Western Dakota
<br />Eastern Dakota
<br />Platte-Niobrara
<br />Middle Missouri
<br />Kansas
<br />Lower Missouri
<br />
<br />Missouri Basin
<br />
<br />77
<br />1,085
<br />74
<br />136
<br />954
<br />373
<br />185
<br />819
<br />
<br />3,703
<br />
<br />Municipal, Industrial, and Rural
<br />Domestic Water Supply
<br />
<br />The economic projections presented for the individ-
<br />ual subbasins were disaggregated to a considerable degree
<br />to assist in determining the location and magnitude of
<br />water supply demands. The water supply studies em-
<br />braced future water demands, based on extrapolation of
<br />current water use practices and tempered by technical
<br />judgments to allow for anticipated trends. Data regard-
<br />ing present water supplies are those reported as of ] 965
<br />from both published and unpublished sources. In some
<br />instances, data on improvements and expansion of
<br />existing su pplies accomplished subsequent to ! 965 were
<br />not available and, consequently, were not included in
<br />the inventory. However, these improvements were taken
<br />into account by the planning groups in determining
<br />future needs.
<br />A detailed description of the studies made to deter-
<br />mine future water supply requirements is contained in
<br />the appendix, "Present and Future Needs." Gross water
<br />demands are based on per capita use rates, or on
<br />industry use rates as established from the basic water
<br />supply studies. The use rates were applied to projected
<br />population and economic activity levels to establish the
<br />gross water demands. The gross demands reflect a
<br />withdrawal requirement at a point of use. These demand
<br />values illustrate the overall magnitude of water required,
<br />but they do not reflect sources of supply, location,
<br />consumptive use, and water returned to the stream for
<br />further use. Therefore, in order to establish needs,
<br />extensive water budgets were prepared for each stream
<br />system which delineate the demand points within each
<br />of the subbasins. In essence, the net demand or need
<br />analysis became a planning function since acceptable
<br />shortage criteria had to be established and a system
<br />
<br />56
<br />
<br />ThennaI
<br />Cooling Livestock
<br />
<br />(Thousand Acre-feet Above 1965 Base)
<br />455 , 44
<br />778 41
<br />349 65
<br />684 92
<br />-252 187
<br />757 136
<br />33 100
<br />350 129
<br />- -
<br />3,154 794
<br />
<br />576
<br />1,904
<br />488
<br />912
<br />889
<br />1,266
<br />318
<br />1,298
<br />
<br />7,651
<br />
<br />analysis made to determine deficiency points and the
<br />alternative ways in which water could be made available
<br />to meet the needs. It follows that this analysis also
<br />indicated those points where supplies would be adequate
<br />through the projection period.
<br />Figure 16 illustrates the typical system analysis made
<br />to determine the net demands, or needs, at various
<br />locational points in a selected stream system. For
<br />example, the Sioux Falls demand point for target year
<br />2020 indicates a gross withdrawal requirement of 21.4
<br />cfs from surface water and 21.7 cfs from ground water,
<br />and the critical low-flow value of 2.6 cfs, or an indicated
<br />deficiency of 18.8 cfs from the surface water demand
<br />alone. Assuming that the deficiencies would be met
<br />through some type of deveiopmt:ntal pmgr:::m such as :l
<br />dam on the Big Sioux River and additional wells, the
<br />return flow to the stream would be 40.6 cfs which
<br />means the consumptive use would be 2.5 cfs. The
<br />planning criteria used and the general relationships with
<br />other functional demands for water are presented and
<br />discussed in the next chapter. Factors of supply,
<br />consumption, and return flows for further use, as
<br />illustrated, establish the demand pattern, but the very
<br />nature of these demands and factors associated there-
<br />with precludes a concise or convenient summation by
<br />subbasin or basin totals.
<br />Since gross demands reflect per capita use rates, they
<br />are sensitive to the projections of future populations.
<br />Short-term projections to the 1980 level are well within
<br />allowable error limits for this type of study. They are,
<br />therefore, adequate for guiding actions to develop
<br />supplies to meet demands before any water crisis would
<br />occur. A similar situation with respect to the long-term
<br />projected trends (to 2020) would also prevail. If
<br />downward or upward shifts in long-term population
<br />growth or in per capita use rates should become evident
<br />
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