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.D~C-~~:-1~9~ ~:3:~~_ . _~ROM fJEPP, REGION B OEP, ..:~.,7~~~~~~~ P,005/OO5 Eft'ectl on SnoWfall and Snowmelt , · Temperature Inereasoa wiD shin tne tJmIng of runoff. eausl~ a diitinc:t Increase In winter runoff and a decrease In spring runoff. Higher elevatIons that receive IlIrg~ amounts of mow will by most Il.ffected by predicted Increases In temperature. Under scenarios of climate change, these rOilons wlll not only receive leos snow, but that snow wlll produce less runoff bc"use evaporation will Increase. ! , i Temperature increase. wllJ also cause . decrease In -...inter snowfall and snowpaclc~ an increase In winter rain. and a fUler and eertler spring U\oWtnelt. Such & shift ili timing of runoff would have dramatic adverst effects on the recreatlonal sid industrY and on the natural eCOsysfems of the regIon. i I These temperature.driven changes could Increase the potential for winter and sprl~ tloodlng ill some pam of the region. I The results sUigest Ihatlncreases in temperature of as little as 20C wO\lld shiftpea~ runoff In the Upper Colorado River Basin to tb. month ~ May ralher tnan Iune.! Etl'ects on Sallnltr an4 Water Quality i . A 20 percent reduction In current annual river flow would cause an Iccrease In sallnit)' In the Colorado RIver or lS to 20 percent, I liifh salinity lev.ls, already a critical concern (or the lower Colorado basin (afTectlllil ell ifornia, Arizona, Nevada. and Mexico), would be greatly worsened by anri decreases In runoff. Even it nInoff !ncre~~es ~ 20 percent, salinity limits will be! exceeded continuously tor lona periodll, I EI1'ecll 01'\ Reservoir Levels IJId Hydroelectricity Generallon .' I . Hydroelectricity productlon and reservoir storage are extremely sensitive to chanies 'I In runo". In the Upper Colorado Basin, a reduction In flow of 10 percent causel average annual storage to decrease by 30 percent and power production to drop by 26 percent. Il flows were ,to drop by 20 percent, power production In the Upper Colorado Basin decreases by 49 pcrcent and storage in the rese1"loirs drops 63 percent. Such impacts would ireatly affect tourism and water recreation, and other i .sourCeS of electricity would have to replece the lost hydropower. In the Lower Colorado Basin, a %0 per "em reduction In lIvcrage annualllow would I caus~ mean annual reductlom in water Slored in the reservoirs of as much as 70 I percent and reductions In hydroelectric power generation of 60 per"Dc. . . . . . . A decrease in runoff of 20 percent would leave Lake Mead essentially empty 2S percent oC the time, and the mInimum water level needed for power sanetatlon wO\lld novor be reached, I , If average runoff Increases by S percent, overall power senerltion jumps by 1 : thousand glgawl1tt.hours (aWh) per yellt, or 11 per~ent, while stora;e Increases by I 14 percent. fn 1he -+ 10 per;ent runoff scenario, power generation Increases by 21 i percent and storage volumes in reservoirs BO up 28 percent. .