SITE INFORMATION AND CORRESPONDENCE_2005-CURRENT

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agricultural salinity objectives for the two Old River sites shall be phased in so that compliance with the objectives is achieved by December 31, 1997. ". . . The SWRCB will evaluate implementation measures for the southern Delta agricultural salinity objectives in the water right proceeding." (1995 Delta Plan, p. 29.) On March 15, 2000, the State Board adopted Revised Water Right Decision 1641, which once again addresses the relationship between water diversions and implementation of Delta water quality objectives. Revised Decision 1641 states: "Water quality in the southern Delta downstream of Vernalis is influenced by San Joaquin River inflow; tidal action; diversions of water by the SWP, CVP, and local water users; agricultural return flows; and channel capacity. (R.T. p. 3668; DWR 37, p. 8.) The salinity objectives for the interior southern Delta can be implemented by providing dilution flows, controlling in-Delta discharges of salts, or by using measures that affect circulation in the Delta. . . . "Even when salinity objectives are met at Vernalis, the interior Delta objectives are sometimes exceeded. (R.T. p. 3677; SWRCB le, Figures [IX-19]- [IX-26]; SWRCB 76.) Exceedance of the objectives in the interior Delta is in part due to water quality impacts within the Delta from in-Delta irrigation activities. (R.T. p. 7794.) In 1987, DWR and SDWA identified flow barriers that could be constructed in the southern Delta to enhance water levels and circulation. The DWR, the USBR and the SDWA have agreed that the salinity problems in the southern Delta can be mitigated using the barrier program. . . . Since 1991, DWR has been installing and operating temporary barriers to assist SDWA diversions. Permanent barriers are proposed as components of the preferred alternative for the ISDP. (DWR 37.) "The construction of permanent barriers alone is not expected to result in attainment of the water quality objectives . . . The objectives can be met consistently only by providing more dilution or by treatment. (R.T. p. 3737.) . . . Modeling shows that construction and operation of the temporary barriers should achieve water quality of 1.0 mmhos/cm at the interior stations under most hydrologic conditions. 8.