SACRAMENTO – With reservoirs rising from December storms, the Department of Water Resources (DWR) has boosted its early-season estimate of next year’s State Water Project (SWP) supply from 20 to 45 percent of most requests.

“This winter’s wet start gives us hope we’ll be able to keep increasing the State Water Project allocation,” said DWR Director Mark Cowin. “But the faucet can shut off suddenly and leave us dry for a sixth year in a row. Drought always looms over California, so we must use water wisely and sparingly.”

Each December, DWR makes its initial estimate of SWP water delivery capability (allocation) for the following calendar year.

The allocation is adjusted – hopefully upward – as hydrologic conditions develop through the rainy season.

Under the initial 20 percent water allocation for 2017, the 29 public agencies served by the SWP would receive only 839,376 acre-feet of the 4,172,786 acre-feet they collectively requested. Under the updated allocation, they would receive 1,894,645 acre-feet.

The initial allocation for this calendar year (2016) was 10 percent of the requested 4.1 million acre-feet, but was increased to 60 percent as storms developed and reservoir storage increased.

When the allocation was updated, Lake Oroville in Butte County, the SWP’s principal reservoir, was holding 1,895,292 acre-feet, 54 percent of its 3.5 million acre-foot capacity and 88 percent of its historical average for the date.

At the same time, Shasta Lake north of Redding, California’s and the federal Central Valley Project’s (CVP) largest reservoir, was holding 3,327,257 acre-feet, 73 percent of its 4.5 million acre-foot capacity and 120 percent of its historical average.

San Luis Reservoir, a critical south-of-Delta storage facility for both the SWP and CVP, was holding 1,155,838 acre-feet, 57 percent of its 2 million acre-foot capacity and 87 percent of its average for the date.

It’s important to note that nearly all areas served by the SWP have sources of water other than their SWP allocation, among them streams, groundwater and local reservoirs.

The last 100 percent SWP allocation – difficult to achieve even in wet years because of Delta pumping restrictions to protect threatened and endangered fish species – was in 2006.

SWP allocations in recent years are as follows:

• 2016 – 60 percent;
• 2015 – 20 percent;
• 2014 –  5 percent;
• 2013 – 35 percent;
• 2012 – 65 percent;
• 2011 – 80 percent;
• 2010 – 50 percent;
• 2009 – 40 percent;
• 2008 – 35 percent;
• 2007 – 60 percent.