Department of Water Resources snow surveyors confirmed that California’s mountain snowpack holds far less water than normal for this time of year.

Manual and electronic readings show that statewide, snowpack water content is only 30 percent of historic readings for the date.  That is a mere 26 percent of the average April 1 measurement, when the snowpack is normally at its peak before it begins to melt with rising spring temperatures.

”The weather news so far this winter has not been good,” said DWR Director Mark Cowin.  “We still have good reservoir storage due to last winter’s storms, but we would like to see more rain and snow this season.”

Due to persistent dry weather, DWR on February 22 dropped by 10 percent its estimate of the amount of water the State Water Project (SWP) will deliver this calendar year.  The delivery estimate – or allocation – was reduced from 60 percent to 50 percent of the slightly more than 4 million acre-feet of water requested by the 29 public agencies that supply more than 25 million Californians and nearly a million acres of irrigated farmland.  An acre-foot is 325,851 gallons, enough to cover one acre to a depth of one foot.

The 50 percent allocation is not severely low, and could be increased if late season storms significantly improve hydrologic conditions.

One area visited by DWR snow surveyors today was off Highway 50 near Echo Summit, approximately 90 miles east of Sacramento. Here are the snow depth and water content readings from four sites in that area:

Electronic readings from remote sensors indicate that snowpack water content in the northern mountain ranges is 31 percent of normal for the date and 28 percent of the April 1 seasonal average.  Electronic readings for the central Sierra show 26 percent of normal for the date and 23 percent of the April 1 average.  The numbers for the southern Sierra are 33 percent of average for the date and 28 percent of the April 1 average. 

Statewide, the snowpack water content is 30 percent of normal for the date and 26 percent of the April 1 average.

DWR and cooperating agencies conduct manual snow surveys around the first of the month from January to May.  The manual surveys supplement and check the accuracy of real-time electronic readings.

Mountain snow that melts into streams, reservoirs and aquifers in spring and summer normally provides approximately one-third of the water for California’s households, farms and industries.  But unless conditions change this winter, water from the snowpack will be substantially less than normal this year.

One bright spot is good reservoir storage carried over from last winter.

Lake Oroville in Butte County, the State Water Project’s principal storage reservoir, is at 100 percent of average for the date (71 percent of 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 94 percent of its normal storage level for the date (69 percent of capacity).  San Luis Reservoir in Merced County, an important storage reservoir south of the Delta, is at 99 percent of average for the date (85 percent of its capacity of 2,027,840 acre-feet).  San Luis is a critically important source of water for both the State Water Project and Central Valley Project when pumping from the Delta is restricted or interrupted. 

Statewide, reservoir storage is 110 percent of normal for the date.

Unusually wet conditions last winter allowed the State Water Project to deliver 80 percent of the slightly more than 4 million acre-feet requested for calendar year 2011. The final allocation was 50 percent in 2010, 40 percent in 2009, 35 percent in 2008, and 60 percent in 2007.  The last 100 percent allocation – difficult to achieve even in wet years because of fishery agency restrictions on Delta pumping to protect threatened and endangered fish – was in 2006.

This winter’s unusually dry conditions to date have principally been caused by a high pressure ridge along California’s coast that has diverted most storms to the north.

Electronic snowpack readings are available on the Internet at:

http://cdec.water.ca.gov/cgi-progs/snow/DLYSWEQ

Electronic reservoir level readings may be found at:

http://cdec.water.ca.gov/cdecapp/resapp/getResGraphsMain.action

See DWR’s new Water Conditions page at:

http://www.water.ca.gov/waterconditions/