Water scarcity in California's Bay-Delta necessitates “hard decisions”

phosphorus concentrations and amounts, water flow, and habitat — negatively affect five delta fishes listed as endangered or threatened, the committee said. 

Successfully rehabilitating the delta ecosystem by targeting how an individual stressor impacts a particular species seems doubtful.  Therefore, hard decisions will need to be made about balancing risks for different water uses, such as allocating water to support economic activity, sanitation, or other needs.  In addition, alleviating any one stressor alone is unlikely to reverse declines in these species, but opportunities exist to mitigate or reverse the effects of many stressors.  To increase the likelihood that actions to rehabilitate the ecosystem are cost-effective, continued analyses, modeling, and monitoring will be needed, the committee noted.   

The release notes that climate change is one of the most challenging and important issues confronting the management and rehabilitation of the delta ecosystem.  It is expected to affect the physical and ecological structure and functioning of the delta as well as the availability of water in the state.  For instance, assessments suggest that many species will be affected by changes in runoff from precipitation and snowmelt, which would likely occur earlier in the year than currently.  In addition, projected sea-level rise and extremes of precipitation could increase the frequency of levee failure and the inundation of islands.  Sea-level rise also has the potential to move more salt water into the delta and alter water quality.  The committee recommended that future planning should include a climate change-based risk model, analysis that incorporates data on the actual changes in delta conditions, and alternative future climate scenarios and their probability.

Additionally, the instability of levees and potential of one levee failure to affect others are liable to be major issues for achieving any measure of water supply reliability or ecosystem rehabilitation.  Continuing the status quo of improving levees will not always be the most environmentally sustainable or economically defensible response in the years ahead, the committee noted.

The lack of integrated, comprehensive planning has made science less useful in decision making for the delta, the committee said.  It recommended that California review water planning and management in anticipation of future circumstances.  This review should devote attention to water scarcity, balanced consideration of all statewide water uses and the practices that govern them, and available engineering alternatives.  In the absence of a review, it would be difficult to resolve delta water management problems in other than a piecemeal fashion. 

“Science is necessary to inform actions and proposals, but it does not provide the entire overview and integration that the committee recommends,” said committee member Henry J. Vaux Jr., professor emeritus of resource economics at the University of California.  “Societal and political considerations are also integral factors in determining the most appropriate policies toward managing the water resources in the delta and balancing the needs of all water users.”

The study was sponsored by the U.S. Department of the Interior and U.S. Department of Commerce. 

— Read more in “Sustainable Water and Environmental Management in the California Bay-Delta”