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<br /> <br />(~ <br />f'0 <br />I~ <br />rJ <br /> <br />CHEiITCAL :':UALITY OF THZ '~A'!'ER <br /> <br />Dissolved-solids Dischar~e ~nd Concentration <br /> <br />Discharge of yater and o~ dissolved solids, and weighted-average <br />concentr~tion of dissolved solids at sel~ctec statio;.5 in the Upper <br />Colorado River Basin are given in Table 6. niese data on discharge <br />repr~5ent the lone-te~ Qveraces that yould have occurred i~ the wete~ <br />use developments existing in 1957 had b~e~ in place and in operation <br />th~ouehout water years 1914-1957. In essence, the data on dissolved- <br />sclids concer.t:"ll.tion represent conditions of 1957. because I:!03t of tbe <br />available che~ic~l analyses ere of s~ples taken late in the 44-year <br />period.. <br /> <br />Sit'-.i.lar data \,tere developed for zrA;IY other stations in the basin. <br />The :-ecords fro!:! ....h1ch. and the :r.ethods by ....h1cb t!Jese a."t!rar:eS ....ere <br />derived are giver. 1n detail in t:le volu:ninous t\"Q r2?Ort~ ",'hich avc.it <br />rublication by the Geological Survey. <br /> <br /> <br />~igure 8 pictures the d~ta of Table 6. ex~~essed as percentages of <br />the outflow f~o~ the Upper Colorado ~iver Basin--thnt is, percentages <br />of \.'ater arId dissolved-solids diSCharges of the Co~orado Ri Y~r cO::ibined <br />vith those of the Paria River, both at Lees Ferry. Ariz.. On this figure, <br />percer;tages are expressed to the r.earest hU:1drcdth so that the sr:!.&.l1er <br />disc:1arces ca.r: be indicated; they are not to be construed to indic:\te <br />great precision 1:1 the quantities, The figure ShC~5 t~at most of the <br />vater co~es fro~ the ~ountnins and freo the hiGh pla~eaus, but that <br />most of tbe dissolved solids cones from the le....er parts of the ba~in <br />....hich receive little precipitation and ~hich yield relatively little <br />vater to the strea=s. The rocks exposed in the mountains ~re ~ener~lly <br />:luch ::iore resistant to the ::;olvent action of ....ater thr:.n are the roel,s <br />that underlie a large part of the lovlands. The activities of man that <br />modify the dissolved-solids ref,1men are largely on the lowlands wh~re <br />the ~re soluble rocks a~d rock debris occur. <br /> <br />For water ye~s 1914-1957 adjusted to 1951 conditions, the aver- <br />age combined vater discharge of the Colorado and Pari~ Rivers at Lees <br />Fer~J, Ariz., is 12,133.100 acre-feet a year; ~e1ghted-averar.e concen- <br />tration is 501 pp~; and average dissolved-solids discharGe is 8,676,300 <br />tens a year. These discharges are ~ot uniformly distributed. Thus, <br />a=ong the three ~ajor parts of the Upper Basin, the Grand division is <br />leest in extent (26.500 square miles or 24 percent of the total area) <br />hut yields the greatest discbar~es of ~ater and of dissolved solids <br />(44 pe~cent and 48 re~cent. ~espectivelJ' of t~ose ~t Lees Ferry). The <br />Green di~~sion is greatest ir. cx~ent (44,100 s~~are ~les or 41 percent <br />of the basin); it yields about 31 percen~ o~ the ~ate" and 33 percent <br />of the dissolved solids. The San Juan di':isi-:l~, 35,30G square miles or <br />35 percent of the urrer basi~1 yield~ o~ly about :) ~ercer.t of the <br />vater ~C a li~e ~ercer.t~ge of the disgo~ved ~olids. <br /> <br />21 <br /> <br />