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January 7, 2004 22 <br />Laguna Reservoir is a regulating storage facility located approximately 5 river miles downstream of <br />Imperial Dam. Operational objectives are similar to those for Senator Wash Reservoir. The storage <br />capability of Laguna Reservoir has diminished from about 1,500 acre -feet to about 400 acre -feet due <br />to sediment accumulation and vegetation growth. Sediment accumulation in the reservoir has <br />occurred primarily due to flood releases that occurred in 1983 and 1984, and flood control or space <br />building releases that occurred between 1985 and 1988 and from 1997 through 1999. Dredging of <br />the Laguna Reservoir to increase its storage capacity is scheduled to begin around CY 2005. <br />Maintenance dredging of the Laguna Desilting Basin, located above Laguna Dam, was started during <br />CY2003 and will continue into CY 2004. It is also planned to lengthen the desilting basin at Laguna <br />by about 1,500 feet in CY 2004. <br />Imperial Dam <br />Imperial Dam is the last diversion dam on the Colorado River for United States water users. From <br />' the head works at Imperial Dam, the diversions of flows for American water users and Mexico occur <br />into the All American Canal on the California side, and into the Gila Gravity Main Canal on the <br />Arizona side of the dam. These diversions supply all the irrigation districts in the Yuma area, in <br />' Wellton- Mohawk, in the Imperial and Coachella Valleys, and through Pilot Knob to the Northerly <br />International Boundary (NIB) to the Mexicali Valley in Mexico. The diversions also supply much of <br />the domestic and industrial water needs in the Yuma area. In CY 2002, approximately 6.141 maf <br />' (7.574 mcm) arrived at Imperial Dam; approximately 5.806 maf (7.161 mcm) is estimated to arrive <br />at Imperial Dam in CY 2003. <br />IYuma Desalting Plant <br />The Yuma Desalting Plant (YDP) was not operated in CY 2003 and is being maintained in a ready <br />reserve status. In calendar year 2002, the amount of water discharged through the Main Outlet Drain <br />(bypass flows) was 119,410 acre -feet at an approximate concentration of total dissolved solids (TDS) <br />of 2800 ppm. The U.S. recognizes that it has an obligation to replace, as appropriate, the bypass <br />flows. Reclamation is preparing a report for Congress that explores options for replacement of the <br />bypass flows from Wellton- Mohawk, including options that would not require operation of the <br />Yuma Desalting Plant. Existing data suggests that operation of the YDP would negatively affect the <br />Cienega de Santa Clara, a wetland of approximately 14,000 acres that is within a Biosphere Reserve <br />in the Republic of Mexico. Reclamation's Yuma Area Office has initiated an environmental <br />' planning effort that will determine the extent of the effects. <br />A short section of the Main Outlet Drain Extension (MODE) near the confluence with the Gila River <br />was damaged during the 1993 Gila River flood and still needs to be repaired. However, seepage <br />from the drain is less than one percent of the ground water flow in the area and is not significantly <br />affecting the quality of the ground water or the Colorado River water. All of Wellton - Mohawk's <br />' drainage flows are expected to be contained in the MODE for CY 2003 and CY 2004. <br />J <br />