PDF _ R40979 - California Drought: Hydrological and Regulatory Water Supply Issues
7-Dec-2009; Betsy Cody, Peter Folger, Cynthia Brougher; 31 p.

Abstract: California experienced severe water supply shortages in 2009, which led to economic disruption across the state, including concentrated losses in agricultural areas in the western portion of the Central Valley—areas already experiencing declines in the housing industry and the economic downturn in general. At the same time, several fish species whose habitat lie at the heart of California’s water supply system and throughout its northern rivers are in decline and some face the possibility of extinction. This situation too has had economic implications, resulting in job and income losses in northern California. The short-term issue for Congress is how to evaluate demands for increasing water supplies that may help some users but may jeopardize the continued existence of several fish species. A longer-term issue for Congress is how to evaluate management alternatives that will protect species, but also help water users and economies that depend on reliable water supplies and healthy ecosystems.

While three years of hydrological drought conditions have created a fundamental shortage of water supply in California, many water users have questioned the extent to which regulatory and court-imposed restrictions on water removed from the Sacramento and San Joaquin Rivers Delta, in order to protect fish habitat, have contributed to water shortages in 2009. Conversely, fishermen and others question to what degree increased Delta pumping in 2004 contributed to fish declines.

Current observations of below-average runoff, reservoir levels, and groundwater levels are broadly comparable to those observed during previous episodes of drought in California. At the end of water year 2008-2009 (October through September), statewide precipitation stood at 76% of average, and water levels in key reservoirs in the state were 69% of average. Groundwater levels from selected wells in the Central Valley are also broadly similar to groundwater levels during two previous historic drought periods. The below-average precipitation, below-average water content of the Sierra snowpack in consecutive winters, and similarity of groundwater levels compared across different periods of California drought support the contention that a multiyear hydrological drought underlies the current water crisis that faces California.

Depending on what baseline is used, total reductions in water exported from the Delta in 2009 are estimated to range from 37% to 42%. Restrictions on water deliveries resulting directly from federal and state regulations, or imposed by courts’ interpretation of those rules, are estimated to range roughly from 20% to 25% of the total export reductions for 2009. The remaining 75%-80% of 2009 export reductions, according to the Department of the Interior, are due to “lack of runoff” (i.e., drought) and other factors. The system of state water rights also has a profound effect on who gets how much water and when, particularly in times of drought or other shortages. Water shortages due to drought and regulatory export restrictions have resulted in unequal impacts on Central Valley Project (CVP) and State Water Project water contractors because of differences in priority of water rights underlying different water contracts. Although combined Delta exports have increased on average since the 1980s and early 1990s, even with implementation of several regulatory restrictions, CVP water allocations for some contractors have been significantly reduced.

This report discusses California’s current hydrological situation and provides background on regulatory restrictions affecting California water deliveries, as well as on the long-established state water rights system, which also results in uneven water deliveries in times of shortages.

 [read report]

Topics: Water

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