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<br />e <br /> <br />w <br />Ul <br />-.J <br />C'..n <br /> <br />e <br /> <br />e <br /> <br />USBRIMWD SALINITY MANAGEMENT STUDY <br />FINAL REPORT <br /> <br />Metropolitan would not have been able to meet the target because SWP water was in short <br />supply and its salinity levels rose to over 400 mg/L. In order to do so, Metropolitan woul <br />have had to stop taking much of its CRA water. Whenever there is a concurrent shortage 0 <br />SWP supply and high salinity, Metropolitan would have no choice but to fully use its CRA <br />water and incur the higher salinity. The key trade-off to be weighed to achieve a salini <br />target is the risk to supply reliability. To achieve the 500 to 550 mg/L target under certain <br />adverse conditions, up to several hundred thousand acre-feet of CRA water would have to be <br />replaced by SWP water. <br /> <br /> <br /> <br />On average, the target would be met in about seven out of every ten years. In the remaining <br />years, hydrologic conditions constrain primarily the SWP with insufficient and often higher <br />salinity supplies, limiting the ability to meet the target. The proposed policy includes clear <br />recognition of this resource limitation and calls upon local agencies to develop and manage <br />their local projects and groundwater to accommodate these inevitable swings in salinity 0 <br />imported water due to natural hydrologic variation. <br /> <br /> <br /> <br />Recognizing the significant constraint of resource availability, the action plan calls for initially <br />meeting the salinity target during the April through September period, which corresponds to" <br />the peak irrigation season and requires proportionally less curtailment of CRA water. That <br />period would be progressively extended to ultimately achieve the target year-round as SWP <br />water quality improvements are realized under the CALFED program. Success in the <br />CALFED process in reducing the salinity of our SWP water is critical to the long-term <br />solution for Metropolitans water. Proposed arrangements for expanded storage and <br />exchanges of CRA water for SWP water will also be important steps to achieving a year- <br />round salinity target within water resource availability constraints. <br /> <br /> <br />Should the anticipated salinity benefits of a CALFED solution or CRA exchanges and storage <br />fall short of need, then the ultimate method of achieving salinity targets may be desalination <br />associated with the CRA. However, given the current state of technology, the costs would be <br />high and there would be significant resource and environmental impacts associated with large <br />quantities of brine disposal. Hence, the action plan calls for an aggressive program of <br />research and development (R&D) of a more efficient desalination technology. This R&D <br />effort is already being initiated by Metropolitan in partnership with interested local agencies <br /> <br />INTEGRATION OF QUALITY AND QUANTITY <br /> <br />The Study shows that management of imported water salinity is important to the regions <br />overall supply mix, especially in regard to local groundwater and recycled water. Although <br />Metropolitans practice is to routinely assess the pros and cons of quality-to-quantity <br /> <br />BOOKMAN-EDMONSTON <br />ENGINEERING, INC. ES-3 <br />O:\LOCALRESIANDYSISALINITYVUNE1998\EXECSUMDOC Last printed 07/20/98 9:23 AM <br /> <br />Executive Summary <br />