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<br /> <br />"-' <br />--J <br />~ <br /> <br /> <br />Chapter 3 <br /> <br />. <br />-~.. <br /> <br />CAUSES AND IMPACTS OF SALINITY <br /> <br />CAUSES OF SALINITY <br /> <br />:"early half of thL" ~altnllY In the Colorado Rl\'er Sy..tcm IS from natural ~ourcc... Saline "pnng~. <br />cro~lOn of sahot: geologic formation... and runoff al] contnbule to thi~ bJckground ..almlt) <br />IrngJ.llOn. rescr\"oir c\apof;J.tion. and mUnicipal and indu...mal (~t&11 \ouree.. male up the balance <br />of the salinity problem In the Color.tdo RI\er Basln Figure ~ sho...... the n:lative amount,> cJch <br />source contributes 10 the ..alimty problem. EPA[ I] estimated the natural sallmt) In the lower hasln <br />was 334 mg/L In 1995. the salmlt) 31 Imperial Dam W;lS n:poned to be 803 mgIL.. a 469-mg/L <br />Increase. <br /> <br />SalimI)' of the Colorado River h3'> been <br />increa..ed by the developmenl of WJter resources <br />In two major \~ays: (I) the addlllon of salts <br />from water u'e and (2) the consumpllOn <br />(depktlon) of water. <br /> <br />The combined effects of water use and <br />consumption ha\e had a slgmficanl impact on <br />salmity In the ColorJdo River Basin, Concern <br />over the damagmg levels of saltnity prompted <br />the BaSin Stales ;md the Federal Government 10 <br />adopt saltmty ~tandards and an ImplementatlOn <br />plan to limit further increases in salinity that are <br />discussed laler In chaplers 5 and 6_ <br /> <br />Sources of Salinity <br /> <br />Naturall47%) <br /> <br />I <br /> <br /> <br />1,l!.1,4'1oj <br /> <br />Figure 2_-Sources 01 salinity tn the <br />Colorado River BaSin. <br /> <br />Agricuiturai Sources ot Salinity <br /> <br />lrngated agnculrure is the largest user of water <br />in the Colorado River Basin and a major <br />contnbutor to the salinity of the s)'Mem. <br />loms[1] found that Imgaled lands in the Up~r <br />Colorado River Basin contribute about <br />3..J. million tons of salt per year {37 percent of <br />the salinity of the river). Imgation Increases <br />salinity (figure 3) by consummg water and by <br />dis<.oh'ing salts found m the underlying sabne <br />..ods and geologiC formations. usually manne <br />shales. <br /> <br />Irrigation Sources of Salinity <br /> <br />ImgatlOn <br />Otlene. <br />/ <br />.------ <br />~.1I1111 " <br /> <br />Coloraao R....er <br /> <br />Irng.ted <br />,.. <br /> <br />~ <br />....- <br /> <br />, <br /> <br />Sallfla <br />SDI~ <br /> <br />-- <br /> <br />- <br /> <br />'Saline ~"ine Sh!lle' <br /> <br />Figure 3-Schematic 01 agncu1tural salt pickup. <br /> <br />9 <br />