Snow Survey Dramatically Shows Dry Conditions in California

March 28, 2013 03:47 PM
Snow Survey Dramatically Shows Dry Conditions in California

State Water Project decreases its water delivery estimate to 35% of requested amounts; Snowpack water content is 52% of normal.

Source: Department of Water Resources

SACRAMENTO– Snow surveyors today reported that water content in California’s snowpack is only 52% of normal, with the spring melt season already under way.

"With most of the wet season behind us, this is more gloomy news for our summer water supply," said Mark Cowin director with the state’s Department of Water Resources (DWR).

After a record dry January and February in much of the state, DWR on Friday decreased its water delivery estimate, or allocation, from 40% to 35% of requested amounts from the State Water Project (SWP).

The 29 public agencies that purchase SWP water requested just over 4 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.

Pumping restrictions imposed this winter to protect Delta smelt and salmon are another reason for the low water delivery estimate.

November and December were unusually wet, but between Nov. 1 and Feb. 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 63% full.

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

Today’s survey – finding snowpack water content at only 52% of normal -- is particularly significant because this is the time of year the snowpack normally is at its peak before slowly melting with warming weather. The season’s final survey on or about the first of May will check the rate at which the snowpack is melting. Snow normally provides about a third of the water for California’s homes and farms as it melts into streams, reservoirs and aquifers.

Electronic readings indicate that water content in the northern mountains is 55 percent of normal for the date, and 55 percent of the April 1 seasonal average. Electronic readings for the central Sierra show 57 percent of normal water content for the date and 57 percent of the April 1 average. The numbers for the southern Sierra are 40 percent of average for the date and 40 percent of the April 1, full-season average.

Today’s conditions, including the State Water Project allocation, could change with April storms.

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.

Electronic snowpack readings may be found at here

Electronic reservoir level readings are available here

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