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<br /> <br />diversion and evaporation, diversion for special use, <br />plugging of wells, and deep well InjeCtion, <br /> <br />w <br />o <br />IV <br />"'" <br /> <br />2. Diffuse SOurce control Involves salt loading <br />and/or conCt'ntrating eflects that are spread over <br />COmparJtively large areas such as minor trJbutary <br />subbds'ns. A general lack of baSIC data has limited <br />the stud,es to tentative plans for control of these <br />sources. The techniques available for control are <br />collection and desalting, collection and evarlOratlon. <br />collection and special use. watershed mandgement. <br />dnd phreiltophyte control. <br /> <br />3. Irrigation source control ,nvolves reductions In <br />the salt loading and conCentratmg effect caused by <br />dissolution of salts m the soil and substrata and the <br />consumptive use of water The techniques <br />applicable to Irrigation source control are improved <br />onfarm irr,gatlon water use. ImprOVl::'d water <br />conveyance systems. ground.water management. <br />return flow management, and evaporat,on <br />suppression. <br /> <br />Additional measures sucn as river system <br />management, watersned m<lnagement, return flow <br />utilization for Other beneflc'al uses, and dilution by <br />additional water sources are also being developed <br /> <br />1.0\(; I!\\(:i: Ol TI.()()h <br /> <br />The Colorado River Water Quality Improvement <br />Program IS only one facet of an overall basin wiltE'r <br />management concept which could be implemented to <br />meet tne objective of mainta,nlrlg salinity <br />concentrations at or below their present level. The <br />basin water management concept enVISions thaI <br />existing and proposed .tructures will be coordinated <br />witn the phYSical features of tne basin to optimize the <br />use and development of the water resources for the <br />greatest economic and social benefits of tnose involvl'<!. <br />There are several allied programs which are expected to <br />beneficially affect the Colorado River sillin,ty, <br /> <br />WEATHER MOOIFICATlON <br /> <br />Weather modification research now in progress IS <br />expected to develop by 1980, a reliable i1nd workable <br />system for IIlcreasing precrpitation. In a limited water <br />area, such <IS the Colorado River Basin, producing 1 to <br />2 million acre. feet of usable new water annually might <br />contribute toward salinity improvement. The highly <br />favorable benefit.cost ratios, the f1exlbititv of use, and <br />the opportunity for obtilming even greater new water <br />yields with adl'anced techniques point to .vea!her <br /> <br /> <br />modification as a very desirable tool for water <br />resources manage,nent. <br /> <br />VEGETATION AND WATERSHED <br />MANAGEMENT <br /> <br />Vegetation and watershed mallagement could <ilso <br />contribute to reductions in salt concentr<itions ot the <br />Colorildo River. Phreatophytes are large contributors <br />to tne salt concentratmg effects in the basin. Research <br />is underway to determine tne efft'ct of treating <br />phreatophyte-infested ilreas With anti.transpirants_ <br /> <br />DESALTING <br /> <br />The coast of soutnern California has been under <br />Intensive study to site large.scale sea water desalting <br />plants. Rl!cent reconnaissance studies nave evaluated <br />desalting pl,jIlts at Diablo Canyon (40 million gallon. <br />per day lmgdl l, Encma-San Ditc'go /40 mgdl, San <br />Diego Refuse Incmerator Project 132 mgdl, and Orange <br />County Water Factory 21 (3 mgd). Ultimately, <br />largl;'.scale, dual-purpose desalting plants may not only <br /><lugment locill munic,pal and industrial supplie. but <br />dlso export or exchange water to meet inland demands <br />SuCh as 011 the Colorado River. As il consequence, <br />dl;'salting IS still expected to have a role In providing <br />future waler supplies for augmentiltion purposes. As <br />such, tne potential ImpaCts of sea water desalting for <br />exchangoO' water and wilter quality Improvement in the <br />Colorado River should be recognized cmd monitored. <br /> <br />CONTROL OF EFflUENT FROM <br />POWER PLANTS <br /> <br />Smce 1970. action has ~en taken with respect to tne <br />ellect of cooling tower blowdown water horn <br />thermal.electric power plants on the salilllty of the <br />Colorado River. Cooling water In the towers <br />evaporates, and salt in the remalnlllg water becomes <br />more cmd more concentrated_ The cooling water must <br />IX' marntamed at or below speCifiC levels of <br />concentrallon, and thiS is done by discharging, or <br />"blowmg down" a portion of the water, ilnd replacing <br />It with fresh wClter. At the present time. there are five <br />large coal.fired tnermal.electrtc generatmg plana either <br />in operation or under construction wlthm the ColoradO <br />River Basm. and otners are planned, that will be <br />diSPOsing of their blowdown water aWily from the <br />nver, thereby removing dissolved salts from the <br />Colorado River system, Water depletions, however, will <br />CC1use some increase in salinity downstream. <br /> <br />25 <br />