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<br />Iol:a <br />t-l <br />Q <br />Q <br /> <br />. <br /> <br />., <br /> <br />. <br /> <br />, . <br /> <br />" <br /> <br />. .' <br /> <br />occurs under almost all of the area. However) many of the wells are small <br />and/or water quality is poor. The alluvial valley-fill aquifers generally <br />have the highest potential capacity for wells, although most are hydraulically <br />connected to the streams. Most of the valleys are narrow, consequently the <br />water withdrawn from the wells affect the streams in relatively short time <br />periods. Because of the low volumes involved, this is not expected to be a <br />significant problem in the basin for many years. <br /> <br />,"-,,'.. <br /> <br />Shallow groundwater is generally of very poor water quality ancl not <br />suitable for agricultural or municipal uses in the Upper Basin. In much of <br />the basin, wells capable of producing 60 Ips (1,000 gpm) or more can be <br />developecl provided that the wells are c1rillecl to sufficient depths. The most <br />"p.roducti'tTe aquifers are in sa.ndstone formations in the southern portion of the <br />bss'fn and in the Green Ri"er formation in the Picear,ce Creek Basi1l,' In most <br />other areas, the wells must be drillecl thottsancls of.ineters deep to tap all of <br />. . 'th1l\ available aquifers. <br /> <br />Groundwater is considerecl as a potantial short-term supplemental water <br />s.u1'ply to energy development. The USDI (1974) estimated that the "average <br />annual replenishment" of the grouncl<<ater supply in the Upper Colorado River <br />Basin is about 500,000 ha-m. This is an estimate of the sum of stream base <br />flows. phuatophyte evapotranspiration, well pUJllpage, ancl subsur.face <<ater <br />movement out of the basin. This quantity c10es not represent a sustained yield <br />since eventual adverse effects on streamflow and phreatophyte vegetation will <br />result from long-term continued depletions. Thus, the long-term reduction of <br />grounclwater inflows to the streams woulcl probably have a beneficial impact on <br />total salt loading although recreational useS and Usheri..s, may be 'c1amaged. <br /> <br />'" <br /> <br />Transbasin Diversions <br /> <br />The more than 10 transmountain c1iversions to the eastern slope of Colorado <br />amounting to about 70,000 ha-m/yr .represents the largest aggregate transbas:in <br />diversion from the UCRB. The Bonneville Unit of the Central Utah Project <br />follows with an expected volume of 20,500 ha-m/yr. There is only one small <br />diversion (320 ha-m/yr) into the basin from the PariaRiver nearT(opic, Utah <br />(Bedland, 1971). The total out-of-basin water exports ar,e approximately <br />110,000 ha-m/yr. . <br /> <br />At the pressnt ti.me, there is a diversion of 900 ha"";yr lI"hichis expecte:c1 <br />to increase to 3,000 ha-m into Douglas Creek from Wyoming tributaries of the <br />Green River. These diversions are part of the Laramie-Cheyenne water supply <br />system (USD!, BR, 1979a). <br /> <br />The Sevier River in Utah receives water from_several sm~11 transmountain <br />diversions from the Colorado River System. There is one diversion from Goose- <br />berry Creek in the Price drainage (USDI, BR, 1964), and there are 13 diver- <br />sions from the San Rafael headwater to the San Pitch Basin (USDA, SCS, 1979d) <br />of the Sevier River. These c1iversions are high in the mountains, of verJ high <br />quality water and individually rarely exceecl 300 ha-m/yr. <br /> <br />23 <br /> <br />.,. <br />