The Department of Water Resources (DWR) has released the 2011 State Water Project (SWP) Delivery Reliability Report.

The 2011 report is the latest in a series of reports on the delivery reliability of California’s State Water Project, the largest state-built and operated water and power system in the United States.

“California faces a future of increased population growth, coupled with the potential for water shortages and pressures on the Delta,” stated the summary.

The newest report updates estimates of current (2011) and future (through 2031) SWP deliveries, taking into account pumping restraints to protect Delta smelt, salmon, and other fish species as well as variations in precipitation and impacts of climate change.

The perspective applied assumes no significant changes will be made to convey water past the Sacramento-San Joaquin Delta or to store the more variable runoff expected with climate change.

“This report is written primarily with the public in mind,” stated DWR Director Mark Cowin. “As a result, it not only provides updated information about the SWP’s water delivery reliability, but is also designed to educate Californians about the SWP and its operations.”

The SWP provides at least some of the water consumed by 25 million Californians and used to irrigate about 750,000 farmland acres. Of SWP water deliveries, about 70 percent goes to cities and 30 percent to farms.

Due to increased public interest in pumping water from the Delta, Cowin noted that a new chapter focuses specifically on SWP exports at the system’s Harvey O. Banks Pumping Plant in the Delta. The report documents that the SWP continues to be subject to delivery reductions caused by fishery agency Biological Opinions intended to safeguard threatened and endangered fish.

Analysts noted that population growth and recent-year legislation on water conservation are among key factors underscoring the importance of accurately assessing the SWP’s reliability of deliveries.

California’s population has grown rapidly in recent years. From 1990 to 2005, the state’s population increased from about 30 million to about 36.5 million. Based on this trend, California’s population could exceed 47.5 million by 2020. By 2050, the population could rise to nearly 60 million — virtually double the 1990 population — according to trends cited in the 2009 Update to the California Water Plan.

Legislation in recent years has focused on encouraging conservation and cutting water use. The Water Conservation Act of 2009 requires that the State of California reduce urban per capita water use statewide by 10 percent by the end of 2015 and 20 percent by the end of 2020.

The 2011 State Water Project Delivery Reliability Report is available online at http://baydeltaoffice.water.ca.gov DWR has issued these reliability reports since 2002. DWR is legally required to prepare and distribute this report to all SWP contractors (those with contracts to purchase SWP water), city and county planning departments, and regional and metropolitan planning departments in the SWP’s service area.

The Department of Water Resources operates and maintains the State Water Project, provides dam safety and flood control and inspection services, assists local water districts in water management and water conservation planning, and plans for future statewide water needs.