NAS: delta smelt 1, farmers 0

“A highly anticipated study of water diversions in California’s Sacramento-San Joaquin Delta has found federal efforts to protect endangered fish “scientifically justified” but added that problems facing delta smelt and chinook salmon are not entirely caused by thirsty farms south of the estuary.

With release of the study today, the National Academy of Sciences stepped into a battle over a pair of federal biological opinions that limit water for farmers to protect the fish. But what many had hoped would clear up controversy over water restrictions has been greeted as another mixed analysis of the region’s overlapping environmental stressors.

The National Academies’ National Research Council said the diversions ordered under the bi-ops from the National Marine Fisheries Service and the Fish and Wildlife Service are sound, but the timing of methods to protect fish from pumps on the south end of the delta — the water source for many farmers in the San Joaquin Valley — is “less well-supported” by science.  …

“The committee concluded that in winter, high reverse river flows from high levels of pumping probably adversely affect smelt. Therefore, reducing the high reverse flows to decrease mortality of smelt is scientifically justified,” the NAS report says. “However, the data do not permit confident identification of when to limit reverse flows of the rivers or a confident assessment of the benefits fish receive by reducing reverse flows. … As a result, the implementation of this action needs to be accompanied by careful monitoring, adaptive management and additional analyses.””  “National Academies Deliver Mixed Message on Calif. Delta Dilemma

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