WASHINGTON — Neutral scientists said Friday that it's too soon to judge the effectiveness of ambitious plans to save fish in the Sacramento-San Joaquin Delta.
While calling the controversial water diversions "scientifically justified," National Research Council scientists cautioned that they cannot yet be definitively evaluated. The split verdict left farmers and environmentalists alike something to seize upon in a much-anticipated report.
"There is great uncertainty," acknowledged Samuel Luoma, a research professor at the University of California at Davis's John Muir Institute of the Environment.
The fate of the infamous Delta smelt epitomizes the ambiguity. Robert Huggett, an oceanographer who chaired the 15-member National Research Council study panel, noted Friday that there are so few smelt that scientists still don't know if the population is rising or falling.
"It's going to take a while to see any change in the system," Huggett said.
Huggett, Luoma and the other panel members spent the past 2 1/2 months reviewing fish-protection measures imposed by the Fish and Wildlife Service and the National Marine Fisheries Service. Congress pressed for the study, following farmer complaints.
The publicly funded, $750,000 report is the first of two planned by the research arm of the National Academy of Sciences. A follow-up report, also expected to cost $750,000, is due in 20 months.
The study formally issued Friday targeted the "biological opinions" issued in 2008 and 2009 by the two federal agencies. These are management decisions that divvy up water between farms and the fish protected under the Endangered Species Act.
"Those changes have reduced the amount of water available for other uses, and the tensions that resulted have been exacerbated by recent dry years," the report notes in an understatement.
Last year, farmers on the San Joaquin Valley's West Side received 10 percent of their normal water allocation. This year, the Interior Department says farmers can expect at least 25 percent.
The research panel concluded that the "concept" of cutting irrigation deliveries to preserve fish population was "scientifically reasonable." At the same time, the scientists stressed that they are "less certain" about what precisely should trigger specific pumping restrictions.
The nuanced conclusions in a study that spanned 69 pages, including background material, allowed advocates to read into it, Rorschach-like, their own priorities.
Environmentalists emphasized the conclusion that federal regulators acted reasonably.
"The report clearly validates the biological opinions," said Ann Hayden, senior water resource analyst with the Environmental Defense Fund. "It's time to stop pitting the economic interests of farmers against fishermen and move forward to find solutions."
But farmers, and their congressional allies, emphasized the enduring uncertainties as well as the report's observation that other reasons besides irrigation pumping have had a "potentially large" effect on fish.
"Much more analysis is needed on the other stressors, their impact on endangered species and the relative significance of the pumps," said Westlands Water District general manager Tom Birmingham.
Democratic Sen. Dianne Feinstein, who provided the study's funding, agreed that the Delta's other problems were "extremely important." They will be studied next, giving farmers hope that other water users will shoulder some of the future Delta preservation burden.
Feinstein added that the Obama administration should "implement the biological opinions with additional flexibility wherever possible," meaning she wants more irrigation water delivered.
The state and federal irrigation system caused at least some of the environmental problems that prompted the irrigation delivery reductions.
Central Valley dams now block much of the original spawning habitat for Chinook salmon and steelhead. Downstream rivers are warmer, rendering fish more susceptible to disease. Giant pumps draw fish to their doom.
Nonetheless, scientists caution that "it is difficult to draw conclusions" about what's most to blame for the fish decline.
"While the (state and federal) pumps kill fish, no scientific study has demonstrated that pumping in the south delta is the most important or the only factor accounting for the delta-smelt population decline," the report states.
Other problems cited by scientists range from pesticides to disease and climate change. These can be complex to track, and difficult to regulate. Global warming, for instance, means snowmelt will occur earlier and faster. This means more winter floods, which change the crucial salinity level in the Delta.
Scientists further caution that the Fish and Wildlife Service and the National Marine Fisheries Service do not coordinate their environmental protection measures, which could potentially cause conflicts.
"These are basically standalone decisions," Huggett said. "The committee believes they should be integrated, one with the other."