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WATER: Winter’s first snow survey set for Dec. 30
NORTHERN CALIFORNIA – California’s hopes for ending one of its worst droughts in more than a century of recordkeeping hinge on the state receiving much more precipitation than normal in 2015.
After three consecutive years of below-average snow and rainfall, surface and groundwater reservoirs are depleted.
Surface reservoirs are unlikely to be recharged to normal levels unless precipitation and snowpack this water year are both well above historical averages.
Abundant snowfall in the mountains would be an important component of a drought-ending scenario.
The Department of Water Resources (DWR) has scheduled the winter’s first manual measurement of the snowpack on Dec. 30.
Generally, California’s snowpack supplies about a third of the water needed by the state’s residents, agriculture and industry as it melts in the late spring and summer.
Due to several December storms, rainfall in Northern California so far this water year has been more than normal, but this precipitation has not generated greater-than-normal snowfall in the Sierra Nevada.
The largest storm blew in from the south, and its warm temperatures resulted in less snowfall than might have been delivered by a colder storm.
Electronic readings of the snowpack show that its water equivalent is only 54 percent of average statewide for Dec. 23.
One Dec. 30 manual measurement will be at the Phillips Station snow course off Highway 50 near Echo Summit. Results of the 11 a.m. survey should be publicly available by early afternoon.
Water year 2014 ended on Sept. 30 as the third driest such period on record; only 1924 and 1977 recorded less statewide precipitation. It was the driest year ever in the San Joaquin Valley, Central Coast and South Coast.
This year also was the warmest year on record in California, according to the California Climate Tracker.
These extraordinarily dry and warm conditions strengthened the drought’s hold on California, and reservoir storage continued to fall through most of 2014.
Shasta Lake, the state’s largest reservoir, normally holds nearly 2.8 million acre-feet (AF) of water in late December but today has only 62 percent of that average amount, 1.723 million AF.
Due to the recent storms, Shasta’s storage has risen since Nov. 29, when it held only 1.046 million AF, its lowest amount of the past quarter century.
Similarly, Lake Oroville, a key reservoir of the State Water Project that normally holds more than 2 million AF in late December, today contains 1.267 million AF, only 59 percent of the average amount.
The lake’s storage had fallen before the recent rains to 898,221 AF on Nov. 21, its lowest storage since 1986.
DWR’s initial water allocation to the SWP’s 29 customers for 2015 was announced on Dec. 1 as 10 percent, an increase from the five percent allocated for 2014. This winter’s precipitation will determine whether the allocation is changed in the months ahead.
The 29 water contractors have requested 4,172,686 AF for 2015. One acre-foot is enough water to cover one acre to a depth of one foot; it can meet the needs of a typical California family of four for a year.
The final SWP allocation for calendar year 2013 was 35 percent of the slightly more than the 4 million AF requested.
In 2012, the final allocation was 65 percent. It was 80 percent in 2011 after an initial allocation of 25 percent. The final allocation was 50 percent in 2010, 40 percent in 2009, 35 percent in 2008 and 60 percent in 2007. The most recent 100-percent allocation was in 2006.