As winter storms continue to fill reservoirs and boost the snowpack, the Department of Water Resources (DWR) today increased its estimate of this year’s State Water Project (SWP) supply from 45 to 60 percent of most requests.
“Our water supply outlook is definitely brighter, but we still haven’t shaken off the effects of our historic drought,” said DWR Acting Director William Croyle. “Californians’ in some areas still depend on bottled drinking water, some reservoirs remain low and groundwater basins are still in decline and have yet to recover. We know from painful history that California winters can go quickly from very wet to very dry. We want to see the snowpack continue to build for the remainder of the wet season.”
DWR initially estimated it would be able to deliver only 20 percent of the 4.1 million acre-feet of SWP water requested this year. That projection (allocation) was increased to 45 percent as reservoirs rose from December storms. Today’s increase to 60 percent of collective delivery requests is due to the atmospheric river storms that have filled many reservoirs and brought flood waters to some areas. With more rain and snow in the forecast, DWR hopes it will be able to increase the allocation further.
Under a 45 percent allocation, DWR would have delivered 1,894,645 of the 4,172,786 acre feet of water requested by the 29 public agencies served by the State Water Project. Under today’s 60 percent allocation, 2,536,267 acre-feet of water would be delivered.
Reservoirs have risen dramatically with runoff from this month’s storms. Major Northern California reservoirs, including Lake Oroville, Shasta Lake and Folsom Lake have been required to make flood control releases to maintain room to safely capture inflow that otherwise could flood downstream areas.
Lake Oroville in Butte County, the SWP’s principal reservoir, early this morning was holding 2,806,473 acre-feet, 79 percent of its 3.5 million acre-foot capacity and 125 percent of its historical average for the date. Shasta Lake north of Redding, California’s and the federal Central Valley Project’s (CVP) largest reservoir, was holding 3,640,765 acre-feet, 80 percent of its 4.5 million acre-foot capacity and 123 percent of its historical average. Folsom Lake near Sacramento, another CVP reservoir, was holding 484,000 acre feet, 98 percent of its historical average and 50 percent of its 977,000 acre-foot capacity. San Luis Reservoir, a critical south-of-Delta pool for both the SWP and CVP, was holding 1,480,803 acre feet, 73 percent of its 2 million acre-foot capacity and 98 percent of its historical average for the date.
As State Water Project allocations change, it is important to remember that nearly all areas served by the project also have other sources of water, among them streams, groundwater and local reservoirs.
The last 100-percent SWP allocation – difficult to achieve even in wet years because of Delta pumping restrictions to protect threatened and endangered fish species – was in 2006. SWP allocations in recent years:
2016 – 60 percent
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
DWR’s California Data Exchange Center Web sites show current water conditions at the state’s largest reservoirs and weather stations.