What is in this article?:
- California‚Äôs second 2012 snow survey shows more dry conditions
- Statewide conditions
- Snow surveyors confirmed that water content in California’s mountain snowpack is far below normal for this time of year.
Statewide, the snowpack water content is 37 percent of normal for today’s’ date and 23 percent of the normal April 1 seasonal total.
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 the real-time electronic readings from sensors up and down the state.
DWR’s initial estimate is that the State Water Project (SWP) will be able to deliver 60 percent of the slightly more than 4 million acre-feet of water requested this calendar year by the 29 public agencies that supply more than 25 million Californians and nearly a million acres of irrigated farmland.
The 60 percent delivery estimate is largely based on the known quantity of carryover reservoir storage. Unknown is how much rain and snow the state will get the rest of this winter. DWR may adjust the SWP delivery estimate to reflect changing hydrologic conditions.
Calendar year 2011 illustrates how weather-driven supply conditions can dramatically change. The initial 2011 estimate was that the SWP would be able to deliver only 25 percent of the slightly more 4 million acre-feet requested. As winter took hold, a near-record snowpack and heavy rains resulted in deliveries of 80 percent of requests in 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 Delta pumping restrictions to protect fish species – was in 2006.
Lake Oroville in Butte County, the State Water Project’s principal storage reservoir, is at 107 percent of average for the date (72 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 99 percent of its normal storage level for the date (68 percent of capacity). San Luis Reservoir in Merced County, an important storage reservoir south of the Delta, is at 119 percent of average for the date (95 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.
(An acre-foot is 325,851 gallons, enough to cover one acre to a depth of one foot.)
Mountain snow that melts into reservoirs, streams and aquifers in the spring and summer provides approximately one-third of the water for California’s households, farms and industries.
Electronic snowpack readings are available on the Internet at:
Historic water content readings from snowpack sensors are posted at:
Archived snowpack water content records:
Electronic reservoir level readings may be found at: