Season’s Final Snow Survey Shows Dry Conditions in California

May 3, 2013 05:19 AM
Season’s Final Snow Survey Shows Dry Conditions in California

Snowpack water content only 17% of normal.

Source: Department of Water Resources

SACRAMENTO – Snow surveyors yesterday reported that water content in California’s snowpack is only 17% of normal, meaning below average water supply this summer.

After a record dry January and February in much of the state, California’s Department of Water Resources (DWR) currently projects it will only be able to deliver 35% of requested amounts from the State Water Project (SWP). 

The 29 public agencies that purchase SWP water requested just over four million acre-feet of water for this calendar year. Collectively, the agencies supply more than 25 million Californians and nearly a million acres of irrigated agriculture.

In addition to the light snowpack and extended periods of little rainfall, pumping restrictions to protect Delta smelt and salmon are another reason for the low water delivery estimate.

November and December were unusually wet, but between November 1 and February 28, fishery agency restrictions prevented DWR from pumping more than 550,000 acre-feet of water from the Sacramento-San Joaquin Delta to store in San Luis Reservoir. Today San Luis – a summer supply pool for both the State Water Project and the federal Central Valley Project – is only 54% full.

"This is the kind of conflict we are working to resolve through the Bay Delta Conservation Plan," said DWR Director Mark Cowin.

The Bay Delta Conservation Plan would reduce harm to fish from altered stream flows caused by the south Delta pumps serving the SWP and Central Valley Project. Pumping there at times causes reverse flows which may disorient or entrain fish. The comprehensive plan's large-scale habitat restoration would also improve Delta conditions for fish and wildlife.

The November and December storms built California’s snowpack water content to 134% of normal by January 2, when DWR and cooperating agencies conducted this season’s first manual survey. Manual surveys and electronic readings have recorded the water content decline since dry weather set in.

Statewide, the season’s second manual survey on Jan. 29 found the snowpack water content at 93% of normal for the date. On Feb. 28, the season’s third manual survey found the snowpack water content at 66% of average On Mach 28, about the time the snowpack is normally at its peak, its water content was recorded at 52% of normal.

Snow normally provides about a third of the water for California’s homes and farms as it melts into streams, reservoirs and aquifers. An acre-foot is 325,851 gallons, enough to cover one acre to a depth of one foot.

The final SWP allocation for calendar year 2012 was 65% of requested deliveries. The initial delivery estimate for calendar year 2011 was only 25% of requested SWP water. However, as winter took hold, a near record snowpack and heavy rains resulted in deliveries of 80% of requests in 2011. The final allocation was 50% in 2010, 40% in 2009, 35% in 2008, and 60% in 2007. The last 100% allocation -- difficult to achieve even in wet years because of pumping restrictions to protect Delta fish -- was in 2006.

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