State Water Project

Five Percent Initial SWP Allocation in 2010

Low levels at Lake Oroville (December 2009). Courtesy of DWR.

The Department of Water Resources has released its initial 2010 allocation for the State Water Project (SWP) — and the allocation is just 5% of the contracted maximum water supply (just over 4.17 million acre-feet). This the lowest in the history of the state project; even lower than in 1993, when the initial allocation was 10%. The allocation is expected to increase as supply conditions solidify in the upcoming year, and some forecasts have suggested that an above average amount of rain may be in store for California this winter. Historically, the final allocation has almost always attained or exceeded the intentionally conservative initial allocation. Initial allocations in the two previous years were both low (25% in 2008 and 15% in 2009), but the final allocations were higher (35% in 2008 and 40% in 2009), and DWR has indicated that the 2010 initial allocation may increase 20-40%. Nonetheless, the Southern California Water Committee has wasted no time, springing (PDF) on this upcoming year’s historically low allocation, declaring it to be a clear sign of the “depth of California’s water crisis” and an indication that the state should pursue a Peripheral Canal  in the Delta — even though such a project, while allowing for a more reliable supply, cannot expand the fixed maximum amount of water made available by nature.

The low initial allocation is the product of current conditions as regards reservoirs, as well as low precipitation and runoff during the previous three-year period of drought. It also reflects the need to comply with restrictions to help protect endangered species of fish in the Delta, whose populations are at historically low levels.

Carryover storage in key reservoirs was at about 69%. This is higher than in 2008, raising a question as to why this year’s initial allocation is less than last year’s (especially given the perhaps opportune timing with the November 2010 election, when voters may pass the water bond and other legislation).  As of December 1, 2009, these are the current conditions (PDF) in the reservoirs, running roughly north to south. Current reservoir levels are well under the historical average at major facilities throughout California:

Reservoir % of Capacity (Current) % of Capacity (Historical)
Trinity 37% 56%
Shasta 37% 60%
Oroville 32% 52%
Folsom 29% 61%
New Melones 46% 85%
Don Pedro 69% 107%
Exchequer 39% 90%
San Luis 30% 49%
Millerton 37% 88%
Pine Flat 28% 76%
Pyramid 97% 104%
Castaic 69% 90%

Meanwhile, precipitation and runoff have both been below historical levels, and the rains from this past October were not sufficient to make up for other shortages. Water year 2009 (which ended this past September) was the third consecutive year of below average precipitation: the 17.45 inches of rain statewide were 76% of average. In November 2009, rainfall in the San Joaquin valley was 13% of average, and rainfall in the northern Sierra Nevada was just 29% of average.

Runoff in 2009 was 65% of average statewide, which is actually higher than the two previous years (53% in 2007 and 60% in 2008), but far less than 173% runoff in 2006, which was a wet year. In the 2007-2009 drought period, runoff for the Sacramento system (including the Sacramento, American, Feather, and Yuba rivers) was about 60% of average, while runoff for the San Joaquin system (including the San Joaquin, Stanislaus, Tuolumne, and Merced rivers) was about 62% of average.

Even if the initial allocation is increased, as expected, this is still a good reminder that we are not yet finished with this drought, and everyone throughout California can and should adjust their habits to conserve water.

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