May 16, 2013
By Nancy Vogel California Department of Water Resources
In the last generation, an amount of water storage roughly equivalent to twice the capacity of Lake Shasta, California’s biggest reservoir, has been developed south of the Sacramento-San Joaquin Delta. That includes nearly five million acre-feet of groundwater storage in Kern County and the Metropolitan Water District of Southern California’s 810,000 acre-foot Diamond Valley Lake in Riverside County. This storage makes it possible for California to hold ample supplies captured in wet years to help withstand dry cycles. But California needs a better way to capture water when it is available. San Luis Reservoir is the largest storage facility south of the Delta that is connected to the State Water Project and Central Valley Project. A full San Luis is essential to making the rest of the south-of-Delta storage system work. Replenishing groundwater banks is a slow and steady process, so “parking” supplies temporarily behind San Luis is the key first step in the south-of-Delta storage process. But in the last few years, the ability of water project operators to fill San Luis has degraded from roughly 80 percent to 20 percent. What happened? The decline of native fish species in the Delta has led to a series of water project pumping restrictions, because pumping in the southern Delta can trap fish and interfere with fish migration patterns. The water projects are no longer able to reliably move water from the Delta during crucial wet periods. California’s ability to store adequate supplies of water is directly tied to addressing the ecosystem problems in the Delta. The Bay Delta Conservation Plan proposes three new intakes on the Sacramento River in the northern Delta in order to reduce harm to fish species, restore more natural flow patterns, and increase water supply reliability. These intakes would deliver water to the existing aqueducts of the state and federal water projects through new tunnels under the Delta. And they would be sized sufficiently to take “big gulps” when the high flows are available. Had the Sacramento River intakes been in place and operating last winter, San Luis Reservoir may have filled to capacity. Instead we enter summer with San Luis half full, the emptiest reservoir in the SWP system. The bottom line? The BDCP is about making today’s storage system work. And it is about establishing the improved conditions to set the stage for additional future storage improvements north and south of the Delta. To learn more about water storage in California, see Appendix 1B of the BDCP consultant administrative draft environmental impact report/environmental impact statement.