The Department of Water Resources (DWR) increased its projected 2011 deliveries of State Water Project water to 60 percent of contractors’ requests, up 10 percent from the December forecast.
In 2010, the State Water Project (SWP) delivered 50 percent of a requested 4,172,126 acre-feet, up from a record-low initial projection of 5 percent due to lingering effects of the 2007-2009 drought.
“Today’s allocation increase reflects robust early winter precipitation and an impressive Sierra snowpack,” said DWR Director Mark Cowin. “But prudent water planning dictates caution as we monitor the rest of California’s rainy season.”
Despite mostly dry conditions this month, precipitation so far this winter is over 66 percent of average for the entire water year (Oct. 1-Sept. 30). December precipitation was 195 percent of average. And near-record snowfall in the Sierra and other mountain ranges assures above-drought runoff into reservoirs and streams this spring and early summer.
Statewide, snowpack water content is more than 150 percent of average for the date and 79 percent of the average, April 1 seasonal total. In addition, most major reservoirs are above normal storage levels.
Lake Oroville in Butte County, the State Water Project’s principal reservoir, is at 101 percent of normal storage for the date after gaining 550,000 acre-feet in December. It currently is holding 2.34 million acre-feet. Remaining winter weather will determine whether if fills to 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 113 percent of normal storage for the date (75 percent of capacity).
It may be a cautionary note that precipitation this month has been light (to date, 13 percent of the January average), but today’s storage and snowpack levels warrant optimism for irrigators and municipal water users.
The State Water Project delivers water to more than 25 million Californians and nearly a million acres of farmland.
Projections of SWP deliveries are adjusted through the winter and early spring as hydrologic conditions develop. DWR is conservative in its projections since farmers and others can suffer if expected amounts cannot be delivered. In November, DWR’s first estimate for 2011 was that it would be able to deliver 25 percent of requests. The initial estimate – always low because it is made before the months of heaviest precipitation – was raised to 50 percent in December.
SWP deliveries were 60 percent of requests in 2007, 35 percent in 2008, and 40 percent in 2009.
The last 100 percent allocation – difficult to achieve even in wet years because of pumping restrictions to protect threatened and endangered fish – was in 2006.
In addition to environmental restrictions, water deliveries are affected by aging equipment and difficulties in recruiting and retaining skilled technical personnel. These issues have reduced DWR export pumping by more than 100,000 acre-feet since last month, impacting the overall 2011 allocation.