With runoff from spring storms boosting reservoir levels, the California Department of Water Resources on Thursday increased its water delivery estimate for most recipients to 60 percent of requests for the calendar year.
DWR’s initial State Water Project (SWP) allocation, announced in December, was 10 percent of requests.
As storms developed, the allocation was increased to 15 percent on January 26, then to 30 percent on February 24 and 45 percent on March 17.
Thursday's boost to a 60-percent allocation is mostly due to March storms that soaked Northern California after a mostly dry February.
Still, the state’s historic drought is far from over.
The storms that have nearly filled key northern reservoirs, including Shasta, Oroville and Folsom, largely skipped the San Joaquin Valley and Southern California where reservoir storage remains low and some communities have seen their wells go dry.
It normally takes more than one wet year to erase the impacts of multi-year droughts, and decades to replenish groundwater levels.
Accurately predicting whether water year 2017 will be wet, dry, or average is beyond the skill of climate forecasters, so California must be prepared for the possibility that next year will be dry.
“Conservation is the surest and easiest way to stretch supplies,” said DWR Director Mark Cowin. “We all need to make the sparing, wise use of water a daily habit.”
The 29 public agencies that receive SWP water (State Water Project Contractors) requested 4,172,786 acre-feet of water for 2016. With Thursday’s allocation increase, they will receive 2,527,629 acre-feet.
Collectively, the SWP Contractors serve approximately 25 million Californians and just under a million acres of irrigated farmland.
The SWP provides the same allocation percentages to cities and farms.
Through the drought that began in 2012, agriculture and many communities have felt the pain of low allocations from the SWP and federal Central Valley Project (CVP), with vast tracts of farmland fallowed and drinking water systems failing in some communities.
It is important to note that nearly all areas served by the SWP also have other sources of water, among them streams, groundwater and local reservoirs.
Key reservoirs are rising from winter storms, but some remain below average for the date.
Lake Oroville in Butte County, the State Water Project’s principal reservoir, early this morning was holding 3,314,718 acre-feet, 94 percent of its 3.5 million acre-foot capacity and 118 percent of its historical average for the date.
Shasta Lake north of Redding, California’s and the CVP’s largest reservoir, was holding 4,184,298 acre-feet, 92 percent of its 4.5 million acre-foot capacity and 109 percent of its historical average.
But San Luis Reservoir, a critical south-of-Delta pool for both the SWP and CVP, was holding 1,013,003 acre-feet, only 50 percent of its 2 million acre-foot capacity and 55 percent of its historical average for the date.
Low San Luis Reservoir levels reflect restrictions on SWP and CVP pumping plants in the Delta in order to protect threatened and endangered fish.
Folsom Lake, a CVP reservoir near Sacramento, has risen to 82 percent of its 977,000 acre-foot capacity, 115 percent of historical average for the date.
Under federal rules, Shasta, Oroville and Folsom have had to make flood control releases to retain storage space for heavy inflow.
Groundwater aquifers recharge much more slowly than surface reservoirs, and many in the Central Valley have fallen to record levels in this drought.
Last year’s (2015) 20 percent SWP allocation was the second lowest since 1991, when agricultural customers of the SWP got a zero allocation and municipal customers received 30 percent of requests. In 2014, SWP deliveries were five percent of requested amounts for all customers.
The last 100 percent allocation was in 2006. SWP allocations in recent years:
– 2015: 20 percent;
– 2014: 5 percent;
– 2013: 35 percent;
– 2012 – 65 percent;
– 2011 – 80 percent;
– 2010 – 50 percent;
– 2009 – 40 percent;
– 2008 – 35 percent;
– 2007 – 60 percent;
– 2006 – 100 percent.
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