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<br /> <br /> <br />L? <br />0:.' <br />'-~ <br />c.,;; <br /> <br />CAUSill OF SALINITY <br /> <br />Lo~er Basin.-_ During 3 co~secutive years (1g4G-51) when there <br />was vcrf little increase in "'-ater discharge beh.een Lees Fer!"".! a.'1.d <br />Gra.'1d Ca..'1yor.. the dissolved-sollds loa.d increased. about 1.3 :niIlion <br />~ons each year. During 1941 the discnarge increased by about 1 million <br />acre-'feet. but the load increased b'J onl:r 2 =illilon tons. In 1952 <br />the 'lis charge increased by 0.2 million acre-feet and the load by 2.2 <br />P-Qllion tons. with the exception of these 2 years the a~'1ual increase <br />in dissolved-solids load during the 30-y,=,s.r peri xl has ranged fr:::m 0.5 <br />million tons to 1.8 million tons. <br /> <br />Ir, 1962 ru,...1off of 14.4 millor. acre-feet at. Lees ";;'e!"!"J. increased by <br />400. A)O acre-feet at Grand Car-yon and the dissal,ed-sollis load increased <br />by hal:. a million tons. By contrast, during the f:lling 0:. Lat:e Powell <br />:he :ollowir~ year, o~ly 1.384,000 acre-feet ~as re~oriej at ~ees Ferry <br />a~l the increase ir: flo-... at ,rand Canyon a;:lour,ted to 246,000 acre-feet, <br />but t~!e dissolved-solids load still incl"eased by r.:ore thar. a hal:' million <br />to:1s. Like',d.se, ....ith a SJ:lB.ll :~lo... ir; 1964 the lissol'Jed-:ooli::h: lO.9.d in- <br />creased by nearly 900,000 tons. The fairly consiste~t salt inflow is the <br />result of the salt load fro~ the salir:e springs w~ich contribute the ma- <br />jor part of the dissolved solids ~~thin this reach. <br /> <br />Large amounts of 1issolved solids are also added to the Color:ldo <br />Ri\"er between :Jrand CAnyon and Hoover Da.~. SCIr.le 01' :ohi::> results from <br />the solution of !:laterial in the bed of Lake Mead. but like thl" l"each <br />abo....e Grand Conyon. :nost is contributed by springs 3J'ld tributary <br />inflows. Recent :;tudies in the Lo....er Ea1;in by the :"eological Survey <br />a.'1a the Bw-eau of Reclamation have provided in1~or......ation !lbout the <br />contribution of spl"ings to the Colorado River bet~~en Glen Canyon Darn <br />and La.~e Mead !U1d to the Virgin River ....hI ch drains into Lake :.lea.d. <br /> <br />1.lajor springn tmd spring-i"ed tributaries annually contribute about <br />760.000 tons of dissolved-solids to the Colorado River bet....een Glen <br />Canyon Dar.l and Lake Mead. Starn runoff in ll:'!l.all tributa.!"ies in this <br />reach of the Colorado xiver contributes an luikno~n. but probably much <br />s::naller. load to the river. The contribution of ':Ussolved solids by <br />:::'lajor sources of infIo.... bet.....een Glen Can.,von and Lake !-lead equals about <br />10 percent of the average dissolved-solids load of the Colorado River <br />at Lees Ferrj. Springs in the lower portion of the Little Colora1o <br />River contribute about half of the :::'l~asured increase in dissolved-solids <br />discharge in the Colorado River bet"..-ec:1 Lees Fer::-j and Grand Canyon. <br /> <br />The ~_~ual dissolved-solids contributions of cajor springs, <br />stre~~. ~d spring-fed tributaries to the Colorado River between }len <br />Ca~/on ~a:::: and Lake :.!eai and t., the Virgin qiver are su.::1!rrarized. in <br />Table B. <br /> <br />26 <br /> <br />