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! : I ! 'j , . ftfects on Snowt'all and Snomn.Jt ' "I Temperature ln~ree.se! will shUt the timing of runoff, caus!ll~ Ii distinctlnctease In winW runoff and a dmease In spring runoff, Hlgper elevatiol1$ that receive largt llIIlOUnl$ of snow will by most affected by predicted IncrCMes /n temperature. 'Under scenarios of climatCl cllange, these regions will not only receive less snow, but that snow will produce les! tuno!f bccau.se evaporation will/ncrel1Sc. . . . i : I ~ Temperature incree.scs will also uuSlla decrelUe in winter snowfall and snowpack, an IncrellSc In winter ral~ and a ta.5ter and earlier spring sno~lt. Such a snltt in timing of runoff would have dramati~ adverse effect! on the reerelltional ski industry and on the natural ecosystems ot the reg/on. I I I ~ These temperature.driven chlUlges could Increase the potential fOf wmter and spring i flooding in some parts of the region, , ~ The results suggest that Increases In temperature at as little as 20C would shift peak . runoff in the U~t COlorado River Basin to the month of May rather than June, I ' " &ff<<ts OD !Ssllllity and Water Quallty .) A 20 perc:ont reduction In current ennual river flow would cause Ill1lncrease in ! salinit)' In the Colorado River of 15 10 20 percent. I . ! High salinity level$, a.lr~ady a critical concern {or the lower Colorado basin (affecting Cal~orni8, AIlzona. Nevada, and Mexko), would be greatly worsened by any decreases in runoff, Even if runoff increoses bX 20 percent, salJnity Ilrrdts will be i exceeded (!ontlnuously for Ions periods. I i ' ~ff<<t.s on Reservoir lAvela and ltydroelectrlclly GeneratIon ~ Hydroelectricity production and reservoir storage Ilte extremely sensitive to changes I Jo runoff. In the Upper Colorado :Bas!n, a reductIon in flow of 10 percent causes I average annual 5torll8e to decrease by 30 percent and power production to drop by i 26 percent. ,Ii flow, were to drop by 20 percent, power production in the Upper , Colorado Basin decreases by 49 percent and storage b the reservoirs drops 63 I percent. Such impa.cts would greatly. Micet lourlsm and water recreation, and other &ource! of electricity would have 10 replace the lost hydropower. , " , I In tbe Lower Colorado Basin, a 20 PQrcent reduction in average annual flow would cause mean annual reductiolU in water stored In the reservolrs of as much as 70 perc,ent and reductions In hydroelectric powor generation of 60 percent. A decrea!e In runoff of 20 percent would leave uke Mead essentltllly empty 2S pU~nt of the time, llnd tl1~ minImum waler level needed for power seneratlon WOlJld never be reached. . i , i I 01 I If average runoff ,Increases by S percent, overall power generation jumps by 1 tho~tlnd gfgaw~tt.hours (GWh) per year, or 11 pe:cent, while stora~e Incre.ases by 14 percent. In the + 10 plm~nt runoff scenario, power generation IDCree!es by 21 per~enl ar.d storage volumes ill reservoir! go up 28 ~r~eDt.