The Department of Water Resources estimated it will be able to deliver 65 percent of requested State Water Project (SWP) water this year. This is up from the 60 percent delivery estimate – or allocation – announced on April 16.
Originally, DWR projected in November that it would be able to supply 60 percent of the slightly more than 4 million acre-feet of SWP water requested, but a dry December, January and February dropped that figure to 50 percent.
A wet March and above-average reservoir storage boosted the allocation back up to 60 percent in April, and today’s increase to 65 percent is due to April’s wetter-than-usual weather.
A 65 percent allocation is not unusually low.
Wet conditions last year allowed the SWP to deliver 80 percent of the slightly more than 4 million acre-feet 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 of water, enough to cover one acre to a depth of one foot. 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 due to pumping restrictions to protect threatened and endangered fish – was in 2006.
April rainfall was 167 percent of normal in the mountainous area between the American River and Lake Shasta that produces much of California’s water supply. The April rainfall total in the San Joaquin River basin was 137 percent of average.
Water content in this year’s sparse mountain snowpack was only 55 percent of normal on April 1, the time of year it’s usually at its peak.
Reservoir storage has been the one consistent bright spot in the water supply picture this year. Lake Oroville in Butte County, the SWP’s principal storage reservoir with a capacity of 3.5 million acre-feet, is 99 percent full (116 percent of average for the date). Lake Shasta north of Redding, the federal Central Valley Project’s largest reservoir with a capacity of 4.5 million acre-feet, is 97 percent full (110 percent of average for the date).
Electronic reservoir level readings may be found at http://cdec4gov.water.ca.gov/cgi-progs/products/rescond.pdf