Document Details

State Water Project Delivery Reliability Report (2009)

California Department of Water Resources (DWR) | August 31st, 2010


The State Water Project (SWP) is primarily a water storage and delivery system intended to help close the gap in California between when and where precipitation primarily falls and when and where most water demands occur. Water from the SWP is a critical component of water supply for the 29 state water contractors, who may also receive water from other sources. While each of the water supply contracts defines the maximum amount of water to be delivered annually, the amount of water actually delivered may be less due to such factors as variable precipitation and runoff, physical and institutional limits on storage and conveyance, and contractors’ variable water demands. For communities receiving SWP water, the reliability of SWP water deliveries is a key factor for local planners and government officials estimating their own water supply reliability.

The 2009 State Water Project Delivery Reliability Report (2009 Report) updates the information contained in the 2007 Report by estimating the amounts of water deliveries for Current Conditions and conditions twenty years in the future. These estimates incorporate restrictions on SWP and Central Valley Project (CVP) operations in accordance with the biological opinions of the U.S. Fish and Wildlife Service (USFWS) and National Marine Fisheries Service (NMFS) issued on Dec. 15, 2008 and June 4, 2009, respectively. The estimates for Future Conditions also incorporate potential changes in hydrology due to climate change projections recommended by the Climate Action Team and sea level rise.

This report briefly describes the SWP and the Sacramento-San Joaquin Delta (Delta), the hub of water deliveries in California. It discusses the general topic of water delivery reliability and how Department of Water Resources (DWR) calculates delivery reliability for the SWP. It then summarizes key planning activities that may affect future SWP delivery reliability. Three areas of significant uncertainty for SWP delivery reliability are discussed. They are climate change and sea level rise, the vulnerability of Delta levees to failure, and operation restrictions imposed by the USFWS and NMFS in response to decreasing populations of endangered fish species. Next, the general approach taken to simulate SWP operations using CALSIM II is discussed.

This report presents the results of CALSIM II studies and compares them to previous estimates. Finally, this report provides guidance on how to apply the delivery estimates to water management plans.

Presented in appendices are detailed CALSIM II simulation
assumptions and results and recent SWP deliveries.

This report does not include analyses of how specific water agencies should integrate SWP water supply into their water supply equation. This topic requires extensive information about local facilities, local water resources, and local water use, which is beyond the scope of this report. Moreover, such an analysis would require deci sions about water supply and use that tradition ally have been made locally. DWR believes that local officials should continue to fill this role.

Keywords

State Water Project (SWP), water project operations