The state shuts down Delta pumps. What does that mean for Santa Clara County’s water supply? We’re doubly threatened

Date: May 31, 2007

SANTA CLARA COUNTY— The California Department of Water Resources (DWR) decision to shut down water pumps in the Sacramento-San Joaquin Delta is a serious concern for the Santa Clara Valley Water District, especially following a prolonged dry winter.  

Sierra Nevada water supplied through the Delta makes up half the county’s water supply. Now that the DWR has temporarily shut down State Water Project (SWP) pumps, the District is evaluating the steps it needs to take to meet demand with less water to import.

“DWR is taking a proactive approach in shutting down the pumps because of the Delta smelt that are clustered near the pumping plants.  We’re sensitive to the need to protect endangered species.  However, this decision will certainly impact our current water supply,” said Tony Estremera, Chairman of the Water District Board of Directors.

The District uses SWP water to replenish the groundwater basins to provide drinking water, and to protect fish habitat in local creeks.

In addition, shutting down state pumps also threatens the county’s federal water delivered through San Luis Reservoir.  If state supplies to the reservoir are disrupted, its water level could fall below the intake that serves Santa Clara County, leaving the district unable to take delivery of its federal supplies. In a worst-case scenario, water users throughout the state could find themselves fighting over water in storage—state against federal, irrigation against urban. 

Extended interruptions in water delivered through the Delta increase the county’s reliance on the groundwater basin, while reducing the supply of water needed to replenish the aquifers, resulting in depleted groundwater basin and higher pumping costs.

Depletion of groundwater also reduces our ability to manage future droughts, and increases risk of land subsidence and saltwater intrusion. Historically, as Santa Clara County developed in the early 1900s, an over-drafted groundwater basin caused land subsidence, and downtown San Jose sank 12 feet. State and federal water deliveries since the 1960s have helped stabilize the basin, but a prolonged interruption in its supply could reverse that trend and permanently damage the aquifer. With the extensive development in place in the valley today, even a small amount of subsidence would cause major impacts.

Interruptions to supplies of water through the Delta will also affect our local environment. Of the county’s 163 miles of local streams used for in-stream groundwater recharge, 129 miles provide habitat for sensitive species. The most severe impacts to aquatic species could occur in 2008, when flows in creeks for in-stream recharge may drop to a trickle.

The shutting down of the pumps demonstrates the vulnerability of the Bay Area’s water supply and the need to invest in water resources and infrastructure, while finding a viable solution to challenges in the Delta.  

If you are interested in an interview, contact Susan Siravo at ssiravo@valleywater.org or (408) 265-2607, ext. 2290.

The Santa Clara Valley Water District manages the county’s major watersheds, including 10 reservoirs, more than 800 miles of streams and large groundwater basins. The water district also provides flood protection throughout Santa ClaraCounty.