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<br />USBR/MWD SALINITY MANAGEMENT STUDY <br />FINAL REPORT <br /> <br />W <br />\'..II <br />c..o <br />;-0. <br /> <br />Urban and agricultural irrigation uses of imported water and recycled water are especially <br />sensitive to drought events. Wastewater agencies also experience difficulty complying with <br />waste discharge permit requirements designed to protect groundwater basins and the <br />environment. Such an experience during the 1987-1992 drought resulted in the Los Angeles <br />RWQCB adopting a new chloride policy for its region. <br /> <br />Where local groundwater or reservoir water is of good quality, the impacts of these episodic <br />conditions are reduced through blending of local and imported water. However, at locations <br />where the changes in imported supplies cannot be mitigated by local supplies, the impact may <br />be acute. Furthermore, agencies using SWP water to blend down high salinity groundwater <br />would experience added blending costs and reduced use oflocal supplies when SWP salinity is <br />high. <br /> <br />The apparent dilemma for the region is that during droughts when the use of recycled wate. <br />projects and marginal quality groundwater are most important, use of some of these local <br />supplies may be constrained by the quality changes in imported supplies unless expensive <br />demineralization facilities are developed. <br /> <br />STATE WATER PROJECT <br /> <br />When the SWP was originally planned, it was to deliver to Southern California 220 mgIL TDS <br />water on average over any ten-year period (DWR, State Water Service Contract, Article 19). <br />In comparison, salinity averages about 325 mgIL in the West Branch and about 250 mgIL in <br />the East Branch (see Figure 2-12 and 2-13). The difference is attributable to salt loading from <br />local stream flow, reservoir evaporation and filling patterns at Pyramid and Castaic Lakes on <br />the West Branch. TDS levels reached as high as 470 mgIL in September 1993. During the <br />1977 drought, TDS in the Delta at the Banks Pnmping Plant exceeded 700 mgIL. Compared <br />to the Colorado River, SWP water salinity changes rapidly, responding to routine seasonal <br />changes and periodic drought and flood events. <br /> <br />BOOKMAN-EDMONSTON Section 2 <br />ENGINEERING, INC. 2-12 Salinity Problems, Impacts, & Technology <br />O:\LOCALRES\ANDYS\SALINITY\JUNE98.2\6SECT2,DOC Last printed 07120/98 10:17 AM <br /> <br />. <br /> <br /> <br /> <br /> <br /> <br />. <br /> <br />. <br />