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Delta Solutions

 

Delta Solutions

Center for Watershed Sciences

Watershed Sciences Building - 1st Floor
University of California, Davis
One Shields Avenue
Davis, CA 95616

(530) 754-9133
FAX (530) 754-9364

Map: Land and Water Use in an Eco-Friendly Future Delta (Lund et al, PPIC, 2008)

Unanticipated Failure of Sutter Bypass Levee in the 1997 Floods (California Department of Water Resources)

The Delta Problem

Water and its management have been at the center of controversy in California for the past 150 years. Evolving and growing demands for water, coupled with changing climate and an aging water supply infrastructure, ensure that controversy will continue into the indefinite future. The increasing complexity of water resource issues in California requires increasingly sophisticated and innovative solutions.

The Sacramento-San Joaquin Delta lies at the head of the San Francisco Estuary and at the confluence of the Sacramento and San Joaquin Rivers.  In the late 1800s and early 1900s the dynamic mosaic of tidal fresh water marsh and floodplain habitats of the Delta were drained and converted to farms, with levees keeping out the tides.  Following land conversion, oxidation of the peat soils of the Delta led to a century of land subsidence, requiring continuous expansion of the levees to reduce flooding.  Today, most of the Delta lies well below sea level--with some "islands" more than 25 feet below sea level--and is held in place by a network of 1100 miles of relatively weak levees.

"...a static, freshwater Delta is no longer sustainable, with the high likelihood of significant disruption to state water supplies."

For the past 70 years, the state and federal government has sought to maintain the Delta as a freshwater system through managed flows from upstream reservoirs and maintenance of the existing levee network.  This policy stemmed from a desire to sustain agricultural activity within the Delta and exports of water through the Central Valley Project, the State Water Project, North Bay Aqueduct and the Contra Costa Canal.  Exports from the Delta supply drinking water to 23 million Californians in the Bay Area and Southern California, and irrigation water to farms in the San Joaquin Valley.  Recent work conducted by the UC Davis Center for Watershed Sciences and other institutions have demonstrated that a static, freshwater Delta is no longer sustainable, with the high likelihood of significant disruption to state water supplies.  At least four hydrologic and geologic processes have the capacity to permanently change the static, freshwater condition of the Delta, principally by increasing the frequency of failure of the levee network.  These include continued subsidence, sea level rise, changing inflows and earthquakes, which combine to cause local to widespread levee failure.   At the same time, the native species of the Delta are undergoing rapid population declines.  Several key fish species that are affected, in part, by Delta export activity, are listed or shortly will be listed as threatened or endangered species.  This has already affected the ability of the state and federal government to export water from the Delta, with indications of greater restrictions in the future with substantial costs to the state’s economy. 

Following the Hurricane Katrina disaster in New Orleans, and the court-mandated reductions in export pumping, the state began an intense planning effort to develop a sustainable future for the Delta.  Two of these efforts—Delta Vision and the Bay-Delta Conservation Plan—are faced with the complex task of developing alternatives for managing the Delta in the future. These efforts are under intense political pressure from many, competing stakeholder groups.