Reports stress water-shortage flow cuts for Bay-Delta estuary

The State Water Board has approved a report suggesting cutting Delta water flows 50% to restore the health of the San Francisco Bay and the Bay-Delta. Yet like so many Delta reports, it is nonbinding and can only be used to develop policy.

The board criteria were issued following a directive by the state legislature in last November’s Delta bill (SB 7X-1).

The San Francisco Bay-Delta is the largest estuary on the West Coast and of critical importance for salmon and scores of other fisheries. It is home to 750 species of fish, birds and other animals, many of which have been in severe decline for decades.

Key Points

• State Water Board uses science to shape draft flows criteria.

• Board directs Bay-Delta water flow cuts of 50% for Delta.

• 1,100 counties are at an extreme risk to have water shortages.

Quick criticism

California farm and water groups were critical. California Farm Water Coalition’s Mike Wade says the report was limited in scope to “flow criteria determinations” and did not look at broader issues. Those issues, such as “habitat, water quality and invasive species,” should be addressed in more comprehensive processes, such as the Bay-Delta Conservation Plan. The report stated that there is a “need for an integrated approach to management of the Delta.”

“This clearly indicates that the State Board understands that fixing the Delta cannot be achieved by simply adding more water,” says Wade.

Dan Nelson, executive director of the San Luis & Delta-Mendota Water Authority, calls the board report “a purely theoretical exercise with no application in the real world.”

This “would require changes in the timing of flows on the Sacramento River, as well as significant increases in volume of flow along the San Joaquin River and through the Delta,” says Spreck Rosekrans, Environmental Defense Fund senior analyst.

“The State Water Resources Control Board is the California agency with ultimate responsibility for the health of these ‘public trust’ resources,” adds Laura Harnish, EDF’s West Coast regional director.

Widespread water risk

More than 1,100 U.S. counties — more than one-third of all counties in the lower 48 states — now face higher risks of water shortages by midcentury as the result of global warming, and more than 400 of these counties will be at extremely high risk for water shortages, based on estimates from a new report by Tetra Tech for the Natural Resources Defense Council, or NRDC.

The report uses publicly available water use data across the United States and climate projections from a set of models used in recent Intergovernmental Panel on Climate Change, or IPCC, work to evaluate withdrawals related to renewable water supply. The report finds that 14 states face an extreme or high risk to water sustainability, or are likely to see limitations on water availability as demand exceeds supply by 2050. These areas include parts of Arizona, Arkansas, California, Colorado, Florida, Idaho, Kansas, Mississippi, Montana, Nebraska, Nevada, New Mexico, Oklahoma and Texas. In particular, in the Great Plains and southwestern United States, water sustainability is at extreme risk.

California counties

Tetra Tech found that without climate change, Contra Costa, Sacramento, San Bernardino and Riverside counties face an extreme risk of water shortages. Factoring in climate change, many of the populous areas of the state enter the extreme risk category.

The report emphasizes that it “was not intended to predict where water shortages will occur, but rather where they are more likely to occur.”

While detailed modeling of climate-change impacts on crop production was beyond the scope of the Tetra Tech analysis, the potential scale of disruption is reflected based on the value of the crops produced in the 1,100 at-risk counties. In 2007, the value of the crops produced in the at-risk counties identified in the report exceeded $105 billion. A separate study compared the Tetra Tech data with county-level crop production data from the USDA; state-specific fact sheets outlining the potential agricultural impacts are at

The Tetra Tech report develops a new water-supply sustainability index. The criteria: (1) projected water demand as a share of available precipitation; (2) groundwater use as a share of projected available precipitation; (3) susceptibility to drought; (4) projected increase in freshwater withdrawals; and (5) projected increase in summer water deficit.

Everyone seems to agree that water is becoming scarce. Still missing is a balanced approach to water solutions.

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HUGE ESTUARY: The San Francisco Bay-Delta is the largest estuary on the West Coast, and of critical importance for salmon and scores of other fisheries. These are levees and in-channel islands north of Staten Island.

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FLOW CUTS NEEDED: The State Water Board has approved a report suggesting Delta water flows be cut by 50% to restore the health of the San Francisco Bay and the Bay-Delta. This is the Middle River at the Highway 4 Bridge in the Delta.

This article published in the September, 2010 edition of CALIFORNIA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.