National Academy of Sciences releases report on Delta smelt


Author:  Damien M. Schiff

The long-awaited report from the federal government's go-to group of scientists, dealing with the Delta smelt and other species protected under the Endangered Species Act, and whether water cutbacks to the San Joaquin Valley are justified to protect these species, is now available (an embargoed copy of the report was published this morning on the website).

More in-depth analysis to follow, but from a superficial read, it looks like the Committee is trying to split the baby:  basically upholding the scientific validity of some regime of water cutbacks, but questioning whether the particular regime imposed by the most recent biological opinions from the United States Fish and Wildlife Service and the National Marine Fisheries Service is justified.


Rather than editorializing, I'll just list here some of the more interesting quotes from the Committee's report.

The committee concludes that reversing or even slowing the declines of the listed species cannot be accomplished immediately.  Even the best-targeted methods of reversing the fish declines will need time to take effect amid changing environmental conditions such as multi-year droughts and continued pressures on the system from other human-caused stresses.

[I]t is scientifically reasonable to conclude that high negative [Old and Middle River] negative flows probably adversely affect smelt populations.  Thus, the concept of reducing [Old and Middle River] negative flows to reduce mortality of smelt at the [State Water Project] and [Central Valley Project] facilities is scientifically justified.

The controversy about the action arises from the poor and sometimes confounding relationship between indirect measures of delta smelt populations (indices) and X2. Although there is evidence that the position of X2 affects the distribution of smelt, the weak statistical relationship between the location of X2 and the size of smelt populations makes the justification for this action difficult to understand.

As a result, the committee concludes that how specific X2 targets were chosen and their likely beneficial effects need further clarification.  It also is critical that the adaptive-management requirements included in the RPA be implemented in light of the uncertainty about the biological effectiveness of the action and its possibly high water requirements.

Based on the evidence the committee has reviewed, the committee agreed that the adverse effects of all the other stressors on the listed fishes are potentially large.

The biological benefits and the water requirements of this action are likely to be sensitive to the precise values of trigger and threshold values. There clearly is a relationship between [Old and Middle River] flows and salvage rates, but the available data do not permit a confident identification of the threshold values to use in the action, and they do not permit a confident assessment of the benefits to the population of the action. As a result, the implementation of this action needs to be accompanied by careful monitoring, adaptive management, and additional analyses.

The controversy about the action arises from the poor and sometimes confounding relationship between indirect measures of delta smelt populations (indices) and X2.

The [biological opinions' reasonable and prudent alternatives (RPAs)] lack a quantitative analytical framework that ties them together within species, between smelt and salmonid species, and across the watershed. This type of systematic, formalized analysis is necessary to provide an objective determination of the net effect of the actions on the listed species and on water users.

At this time, the best that can be done is to design a strategy of pumping limitations that uses the best available monitoring data and the best methods of statistical analysis to design an exploratory approach that could include enhanced field measurements to manage the pumping limitations adaptively while minimizing impacts on water users. Such an approach would include a more explicit and transparent consideration of water requirements, despite the variability in environmental conditions and water demand; and population models to evaluate the combined effects of the individual actions.