[Sacramento] – As winter storms slowly boost water supply, the Department of Water Resources has increased its water delivery estimate for most recipients from 10 percent of requests for the calendar year, as announced in December, to 15 percent.
“Our modest increase underscores the fact that we still have a critical water shortage after four-plus years of drought that we don’t know when will end,” said DWR Director Mark Cowin. “One look at our low reservoirs tells us that we need a lot more wet weather before summer.”
Although there is no exact formula for ending the drought and conditions vary region by region, a rough guidepost is that approximately 150 percent of average winter precipitation – rain and snow – would significantly ease statewide conditions, with the major exception of groundwater depletion.
The State Water Project (SWP) delivery estimate (allocation) may be increased further if storms continue to build rainfall and snowpack totals. The 29 public agencies that receive SWP water (State Water Project Contractors) requested 4,172,786 acre-feet of water for 2016. With today’s allocation increase, they will receive 631,115 acre-feet.
Collectively, the SWP Contractors serve approximately 25 million Californians and just under a million acres of irrigated farmland. It is important to note that nearly all areas served by the SWP also have other sources of water, among them streams, groundwater and local reservoirs.
Key reservoirs are beginning to rise from early winter storms, but remain low. Lake Oroville in Butte County, the State Water Project’s principal reservoir, early this morning was holding 1,366,061 acre-feet, 39 percent of its 3.5 million acre-foot capacity and 60 percent of its historical average for the date. Shasta Lake north of Redding, California’s and the federal Central Valley Project’s (CVP) largest reservoir, was holding 2,138,566 acre-feet, 47 percent of its 4.5 million acre-foot capacity and 71 percent of its historical average. San Luis Reservoir, a critical south-of-Delta pool for both the SWP and CVP, reflects the same trend of lower reservoir storage this year. San Luis was holding 641,729 acre-feet, 31 percent of its 2 million acre-foot capacity and 41 percent of normal for the date. Folsom Lake, a CVP reservoir near Sacramento, is holding 398,523 acre-feet of its 977,000 acre-foot capacity, 79 percent of average for the date.
Though still critically low, many reservoir levels have dramatically risen from recent storm runoff. Groundwater aquifers recharge more slowly, with many in the Central Valley sinking toward record levels.
Last year’s (2015) 20 percent allocation was the second lowest since 1991, when agricultural customers of the SWP got a zero allocation and municipal customers received 30 percent of requests. In 2014, SWP deliveries were five percent of requested amounts for all customers.
The last 100 percent allocation – difficult to achieve even in wet years largely because of Delta pumping restrictions to protect threatened and endangered fish species – was in 2006. SWP allocations in recent years:
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
2006 – 100 percent
Governor Edmund G. Brown Jr. declared a drought state of emergency on January 17, 2014 and followed up with statewide water conservation mandates. Since then, the state has been swept by drought-fueled forest fires, vast tracts of farmland have been fallowed and some communities have scrambled for drinking water.
Long-range weather forecasts are uncertain, and there is no way to know if this winter will deeply dent the state’s historic drought.