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Colorado River Basin Salinity Control Project Coachella Canal Unit, Title I Division lUnder Constructionl California: Imperial and Riverside Counties Lower Colorado Region Bureau of R.''')UIIIUtioll The Coat'hclla Canal Unit is ont' of three components authorized under Tille I of Ihe Colorado Rh'er Basin Salinity Control Act. The other Iwo components are the Desalting Complex Unit and (he Protc(,ti\.t~ and Regula- tory Pumping Unit, whit.'h are dis('ussen in ~eparate IJrot.'hures. The original123-mile C08t:hclla Canal was a feature of the Coal'hella Division of lhe AII.American Canal S)'stem, Houlder Canyon ProjC('1. The Coachella Canal delh:ers Culorado Rivcr water from the AII-Ameril'81l Canal 10 irrigate 78.5:30 al'res of agriculturallanrl in the Coachella Valley of California. Originall~', the first 86 miles of lhe waterway' wt'rc unlined. and the remaining 37 miles were ('OI1l'retc linen. The original canal also had six turnouts to sen'e ahout 6.500 acres of non.ferieral land on Imperial East Mesa, of which ahout ,)00 acres ha\'e heen deyeloped. The l'apacity of the original ('anal was 2.500 l'ulJic feet per second al the lurnout from the All. '\meriran Canal wlwre it began. ann was necreased through SUl'l'c~si\'e readles to 1.:300 cubic feet per second at the beginning of the last 37 miles - Ihe lined section (terminal end). ~t;{~>.8~f::~<:;(~j;}~1JJ!fl ,._.::.i1~_-:"'~.... _."~_".-. '. " ~~':~~~:'Y{.}~;;{~~:~?-7:Jlj;?~" :I;~ .'-.:~~...;...~,:i..tt:~...._ ;...:.;. ~ ; w ,~":. -." ,. .", "~-...C:-,."" I - --. -.t & " -.... ~ i , ~. -, f t - w -' '-,."! I I I J. -~ - ~.." ...._... " " ...~..~ ,:.-. . It Coachella Canal Dh-el'8ion Rcp,inn Rl'\i~ion J/HI (Frolll ProJ('('( Ilala Roo~) After the ('anal's l'omplelion in 19-t.8, seepage losses developed along Ihe 86.mile unlinen sed ion. The initial 49 miles of Ihe original 86.mile unlined ~e('tion traversed the ('oarse. sand soils of Imperial East Mesa where the most st'H're seepage Ot'(:urred. AI Ihe cana!"!" slarling point. the turnoul from the AII.American Canal at Drop No. ]. Ihe a\'erage annual rli\'ersions were 497.800 acre-feel. Of Ihis amount, an e!"timated 1I\'crage of ]68, 470 acre.fect per year harl heen lost hecause of canal ~eepagc. The primar~ purpose of the Coachella Canal Unit is 10 redul'e the water losses in the Coachella Canal by l'on~lrlll'ling a new l'OI1l'rete.linen ("anal to replal'e the inilial49 miles of the unlined section of the canal. This 49.mile replacement e\tel1lls from the lurnout al Drop No.1 on Ihe AII.American Canal to mile post 49, .....here the repla('ement rejoins the 37-mile unlinen seclion of the original ('anal just upstream from siphon No.7. Then. Ihe 37.mile unlinefl sel'lion joins lhe last 37 miles of l'anal. Ihe ani)' originall)' lined section of the ('anal. The water sa\'en IJ)' the new lining willlemporarily he used to replacc the water which is bypassed 10 lhe Sanla Clara Slough: the h)'passed water is not counlefl as part of l\1exi('o's allotment of Colorado Rh'er water. PLAN I The plan ('ailed for II principal feature of the unit to he a new 49.mile canal which replan>rlthe initial 49 miles of Ihe original 86.mile unlinerl seclion. Water mcasurements of flow qw.tnlities are made at t",:o par. shall flume!". one at each end of the new canal. W aler quanlities arc also measured at each lurnoul. Olher ft'alures l'unsist of four lll'W check drop slru('.tures, eight siphons. si~ irrigation turnouts. and operating roans. The existing Coachella Canal Turnout, siphon No.7. and flood protecti\'e work.s are retained with only minor modification. All other existing structures on the firsl 49 miles of the canal hll\'e heen abandoned, including Ihe replacen unlined section of the canal. The new ('anal is designed to al'l'ommOlJate a flow of 1,550 ('ubi<: feet per second.