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<br /> <br /> <br />Chapter 5 <br /> <br />SALINITY CONDITIONS <br /> <br />n <br />0' <br />~, <br />:.. <br /> <br />" The Colorado Rivet SyS[em is narurally very saline. Over 9 miIJion Ions of salt are carried down <br />{he flYer every year. This 5.1][ is diluted by the flow of (he river. and depending upon the qUJmity <br />of flow, salimty can be relatively dilute or concenlraled. Since the flow In the river is directly <br />affecled by climatic conditiol15. salinity in anyone year may double (or halve) due [0 extremes in <br />runoff. Because this natural \'ariabi/j[)' is vinually uncomroJlable. the seven Basin Slates adopted a <br />non-degradation Water quality slandard which is unique [0 this river system. <br /> <br />Salts have few. if any, negative health effects. Their main impact is economic. Presem economic <br />damages range belween 5500 million and 5750 million per year, primarily due 10 agricu]rura] <br />damages. corrosion, and plugging of pipes and Water fi:uures. The seven Basin Slates have agreed <br />to Itmit this Impact and adopted a standard which requircs that salin][)' lev'cls nO[ increase (from the <br />197~ levelsJ due to future Water development. Salinity levels measured in the river may be low or <br />high due <0 climatic condllions. bu. .he goal of .he Slandards and lhe Colorado River Basin Salinily <br />Comrol Program (SalinilY COntrol Program) is 10 offset (e]iminale) the economic effects of <br />aJdltional water developmenl. <br /> <br />~ <br />I <br />I <br />I <br /> <br />The Bureau of Reclamation (Rec]amation) and the U.S. Geological Survey (USGS) Continuously <br />monitor the flow and salmity of the river system through a nelwork of 20 gauging stations. <br />Reclamation evaluales the data collecled as pan of its progress repons usmg hydrologic and <br />computer techniques to detenmne if sufficient salinity comro] is in place 10 offsel the impact of <br />water developmem. In 19Q9. the actual salimlles in the Colorado River Basin were within the <br />standards due to Ihe storage of relatively fresh Water In the lov.:er basin reservoir system. <br />However. as the impacts of recem waler developmem work their way through the hydrologic <br />system. saltnilY will increase. At this time. there is not enough salinity Control in place to offset the <br />el.:isting level of development. As Ihe Basin Stales Continue 10 slowly develop their Water. more <br />sallnit)' comrol v.'ill ~ needed to prevem further degradation of the riv'er s)'stem. <br /> <br />FACTORS INFLUENCING SALINITY <br /> <br />Salinity in the Colorado River Basin is directly Influenced by reservoir storage. Waler resource <br />developmem. sa]inilY camro!. climatic conditions. and natural runoff. Before any Water <br />deve/opmem. the salinity of spring runoff was often be/ow ~OO milligrams per liter (mg/l) <br />throughout the Colorado River Basin. But salinl!Y in the lower mainslem was often well above <br />1.000 mg/l during the low flow momhs-v.hich was most of the year-since there were no <br />reservoirs to catch and Slore the spring runoff. Water storage has all but elimmated seasonal <br />swings in salinil)'. <br /> <br />Allhough seasonal swings in salinir) have been grearly reduced, wide annual fiucrua.ions in saliniry <br />are still observed. "'arural. chmalic variatIOns in rainfall and snov.me]t runoff continue 10 cause <br />IJlge )ear-Io.year differences in both fiow and salinily-in some cases, nearl) doubling .he saliniry <br />in the river. <br /> <br />65 <br /> <br />- <br /> <br />