Saving Sierra Nevada Rivers from Misguided Dam ProposalsAugust 29, 2011 | Dams & Dam Removal, Water Supply
The South Sutter Water District recently proposed the 350-ft Garden Bar dam on the Bear River approximately 45 miles northeast of Sacramento, California (Map1). Garden Bar Reservoir would permanently flood approximately 2,500 acres in the lower Bear River, 900 of which are permanently protected public open space (Map2).
At a cost of nearly half a billion dollars, South Sutter claims Garden Bar dam would reliably provide less than 100,000 acre-feet of water, enough for about 100,000 homes. Much of the water would be sent great distances through aqueducts, as far San Bernardino Valley, some 470 miles south.
South Sutter’s “Garden Bar Reservoir Preliminary Study” contains so many caveats and admitted omissions that even this meager amount of water supply seems highly doubtful. For example, they assume that existing river flows will remain unchanged despite the fact that the 20 dams upstream will undoubtedly reduce available water as early as 2013 when they receive new operating licenses from the federal government.
South Sutter also ignores the State Water Board’s Delta Flow Criteria, which could require substantially more water to flow freely from the Bear and other Sierra rivers through the Delta than currently does, almost certainly eliminating hope for any “extra” water.
In addition, they ignore the ongoing effects of climate change, which is expected to reduce the Bear River’s total annual water supply by up to 8% or more, and shift the timing of most runoff to winter instead of spring. It is in winter that the State Water Board’s criteria would significantly reduce how much South Sutter could store in a reservoir.
These and many other uncertainties surrounding water supply and transport issues have caused potential project partners to prematurely pull their support, such as Castaic Lake Water District in Los Angeles County.
American Rivers is working with local conservation group Sierra Watch and others to protect the Bear and other Sierra rivers and landscapes from misguided ideas such as the Garden Bar dam. Water supply alternatives should be evaluated, not only for the water users near the proposed Garden Bar Reservoir, but also for southern California.
The biggest water supply agency in southern California, the Metropolitan Water District (MWD), and other agencies have adopted a "portfolio approach" [PDF] that incorporates alternative supply sources such as water recycling, desalinization, groundwater use, and demand management programs.
The diversified portfolio would reduce dependence on water transfers from northern California from 56% to 25%.
Reducing dependence on diverted flows while incorporating a suite of water source alternatives significantly increases the reliability of water supply for southern California (modeled at 98% up to year 2020).