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<br /> <br />l'\ <br />'-l <br />-, <br />~. <br /> <br />Chapter 2 <br /> <br />DESCRIPTION OF BASIN <br /> <br />~, <br /> <br />The con.qrucUon and filling of the marnstem reservoIr" of the Coloradt1 Rl\er R.bln ffigure J I <br />h;J\'e brought about sigmficant changes In the flo\.\/ patlem" of the fiVer. Th"" 8,.\>.tn encompas~es <br />POrtIOn\. of ,even BJ~rn St.::nc\: Wyomrng. Ctah. Colorado. :'\e\'JdJ. :--"ew .\I.:\ICO. Anzona. and <br />CallfornlJ The (1\'I.:r f10\\~ more than 1.400 miles from liS headwater, In Wyoming: and Colorado <br />It Joms W Hh tnbutarles from Utah and ;o..:ew .\IC:>':ICO; flo...... lhrough the Grand Canyon: provIdes <br />SIJte boundanes for :"evada. Arizona. and CalifornIa; flows through the Republ1c of :\k\ICO; and <br />termrnates in the Gulf of CalifornIa The m~l.lnslem of the Colorado RIver pro\ Ides munICIpal and <br />IndustnaJ WJler for more than 18 million people and Irrigation Water 10 I 7 million <tere." In th~ <br />Cnited Sta{~". <br /> <br />CLIMATE <br /> <br />E\treme,> of temp~r..lture In Ihe BaSin range from -50 10 130 degrce~ Fahrenheit. The nonhern <br />portion of {he Ba~in IS characteril~d by shon. wann summer~ <Ind long. cold '-\'Inters; and many <br />mount;un areas are bbnk~led by deep snow all Winter. ~fuch of the area consists of high basins or <br />valleys wllh cold winters and hot, dry summers. The southern desert portion of {he Basin has <br />long, hol summers. pracllcally continuous sunshine, and almost complete absence of freeZing <br />temperature:,>. Ramfall a..'erages 2.5 inches per year in Ihe southern ~nd of th~ Basin, while total <br />pr~cipHallon In the mountains reaches ..m to 60 inches annually. <br /> <br />HYDROLOGY <br /> <br />Th~ Colorado River begins wh~re peaks rise more than 14,000 feet In the nOnhv.eSI portIOn of <br />Rocky .\tountam ~ational Park in Colorado, 70 miles nonhwesl of Denver. It meanders southwest <br />for 640 miles through the Upper Basin to Lee Ferry, Ihe di..iding pomt for lhe upper and lower <br />pOrtlon~ of the Basm. <br /> <br />The Green River, the major tributary to the Colorado River, mes in western Wyoming and <br />dlsch;uge... mto the river In southeaslern Utah-730 nver miles soulh of Its origin and 220 miles <br />..lbO\~ Lee Ferry. The Green River drains 70 percent more area than the Colorado River above <br />lhelr Juncllon but produces only about three.founhs as much water The Gunlllson and San Juan <br />Rivers are the olher principaltnbutanes of Ihe Colorado River In the Upper Basin. <br /> <br />The Colorado River Basin has a 101.11 area of approximately 2.w.000 square mdes, C~lng an <br />average annual nalUral flow of about 15 millIOn acre-feet at Lee FelTY. Of thiS now. more than <br />5 mdlion acre-feet per year are e'poned to Ihe Arkansas and :..tissoun Rl\er Basms, the Great <br />B3sJIl. SOuthern California. and Ihe Rio Grande Basin. <br /> <br />The Colorado River 8asJIl is relatively arid. Compared 10 olhers. such as [he Columbia River <br />Basin "hich drams 3pproximately the same area, il carries a much smaller flow. Table I shows <br />that v.hlle the Basm IS one of the major dram3ge basms in the COni mental Cnited Slates. its runoff <br />is aoout equal to that of the Dela"are River. which drains a much smaller area, <br /> <br />5 <br />