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WATER: Department of Water Resources decreases State Water Project water delivery estimate
The Department of Water Resources (DWR) has decreased this year’s water delivery estimate from 40 to 35 percent of requested State Water Project water.
The reduced allocation is due primarily to a record dry January and February in Northern California, where key reservoirs capture water to supply millions of Californians.
Weather so far in March also has been relatively dry. California normally receives more than 90 percent of its rain and snow from December through April.
Pumping restrictions this winter in the Sacramento-San Joaquin Delta to protect salmon and Delta smelt also limit the ability of DWR to meet requests for State Water Project (SWP) supplies.
November and December were relatively wet, but between November 1 and February 28, restrictions to minimize harm to native fish prevented DWR from pumping more than 550,000 acre-feet of water from the Delta to store at San Luis Reservoir. San Luis is a critical summer supply pool for the SWP and the federal Central Valley Project. Today the reservoir is 63 percent full.
If DWR did not have to rely solely on its south Delta pumping plant and had a north Delta diversion on the Sacramento River, as proposed by the Bay Delta Conservation Plan (BDCP), the department could have moved water to San Luis Reservoir while meeting existing salmon and Delta smelt protections.
The ability to divert that water in the wake of winter storms likely would have led to a higher allocation for SWP water supply contractors this year.
“We reduced pumping this winter to protect fish from reverse flows in south Delta streams that entrain fish and divert them from their migratory routes,” said DWR Director Mark Cowin. “The new intakes and habitat restoration proposed by the BDCP would mitigate this problem. These ongoing conflicts will continue until we fundamentally change the way we convey water from the Delta.”
Last week, the California Natural Resources Agency began releasing draft chapters of the BDCP, which aims to both halt the decline of native fish populations in the Delta and stabilize the delivery of water from the Delta. For more information, visit www.baydeltaconservationplan.com .
The 29 public agencies that buy water from the SWP have requested slightly more than four million acre-feet from the project. Together, these agencies supply water to 25 million Californians and nearly a million acres of farmland.
This new water delivery estimate may change if hydrologic conditions improve.
Water content in the snowpack, which begins to melt around the first of April, is 57 percent of normal for the date and 56 percent of a full season’s average.
Reservoir storage will help California cope with dry weather. Lake Oroville in Butte County, the SWP’s principal storage reservoir, is at 109 percent of average for the date (82 percent of its 3.5 million acre-foot capacity). Lake Shasta north of Redding, the federal Central Valley Project’s largest reservoir with a capacity of 4.5 million acre-feet, is at 103 percent of its normal storage level for the date (82 percent of capacity).
Reservoirs will supply most water needs this year, but successive dry years would bring drought conditions to some regions of the state.
The final allocation of SWP water in calendar year 2012 was 65 percent of requested deliveries. The allocation was 80 percent in 2011, 50 percent in 2010, 40 percent in 2009, 35 percent in 2008, and 60 percent in 2007.
The last 100 percent allocation – difficult to achieve even in wet years because of restrictions on Delta pumping to protect native fish species – was in 2006.