National Academies news: Managing the Columbia River

03/31/04

WASHINGTON -- If Washington state issues additional permits for water to be diverted from the Columbia River for farm irrigation, it should do so only under the condition that withdrawals can be stopped if river flows become critically low for endangered and threatened salmon, says a new report from the National Academies' National Research Council. Salmon are at increased risk during periods of low flows and high water temperatures, conditions that are most likely to occur during the summer months when demand for water by farmers is greatest, the report says.

"Whether or not to issue additional permits is a decision to be made by the public and policy-makers, but if the withdrawals are allowed, there should be enough flexibility to halt them if river conditions become too severe for the salmon," said Ernest Smerdon, chair of the committee that wrote the report, and retired vice provost and dean, College of Engineering and Mines, University of Arizona, Tucson.

The report was requested by the Washington State Department of Ecology, which asked for an evaluation of the effects of additional water withdrawals of approximately 250,000 acre-feet to 1.3 million acre-feet per year, roughly the volume sought in currently pending applications for additional water withdrawals. An acre-foot is the quantity of irrigation water that would cover an acre to a depth of one foot -- equal to 325,851 gallons.

Over the course of the 20th century, salmon runs on the Columbia River dwindled from around 16 million per year to only 1 million per year. Their numbers have rebounded slightly in recent years, mainly because of favorable conditions in the Pacific Ocean, to which young salmon migrate before returning upstream to spawn.

The committee reviewed many competing scientific hypotheses and models that attempt to explain the effects of various environmental conditions on Columbia River salmon. There is no scientific consensus on which environmental factors pose the greatest threat to salmon, the committee said, but scientific evidence does show that when extremely low flows or excessively high water temperatures occur, pronounced changes in salmon migratory behavior and lower survival rates can be expected. Several dams on the Columbia have slowed the river's velocity and smoothed out much of its natural variability, although its water levels and velocity still fluctuate considerably on a daily, seasonal, and yearly basis, the committee said. It also emphasized that policy-makers must be willing to develop a sound, comprehensive water management plan despite the scientific uncertainties.

Because the Columbia River basin extends across seven states, many Indian reservations, and one Canadian province, the committee urged the jurisdictions involved to convene a forum for documenting and discussing the potential effects of proposed water diversions. Making decisions about diversions on a case-by-case basis without considering the basinwide cumulative effects will contribute to degraded conditions for salmon, the committee said.

Several water management approaches being considered by the state's department of ecology were reviewed by the committee. It recommended against any conversion of current water rights to so-called uninterruptible status -- an approach in which a farmer gives up rights to a certain volume of water in exchange for a guaranteed minimum level of water every year -- because this method would decrease flexibility in times of low flows or high water temperatures. On the other hand, the committee found the department's market-based proposals appealing because the trading of water rights could lessen the need for further water diversions. Regardless of the approaches it chooses, the department of ecology should adopt the principles of adaptive management, where decisions are made and adjusted based on continuous scientific experimentation and monitoring.

Source: Eurekalert & others

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