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Idaho Report Claims Flow Augmentation Unjustified

by Barry Espenson
Columbia Basin Bulletin - November 3, 2000

A report produced by Idaho agency officials and researchers says that federal studies used as justification for Lower Snake River flow augmentation do not hold water.

Flow augmentation, called for in existing and proposed federal hydrosystem biological opinions, is drawn from Idaho reservoirs created for irrigation, recreation and other uses. The increased flows outlined in National Marine Fisheries Service biological opinions are intended to aid migration of Snake River salmon species listed under the Endangered Species Act.

Despite evidence from investigations carried out by NMFS, the U.S. Fish and Wildlife Service and Nez Perce Tribe that show there is a correlation between flows and Snake River fall chinook survival, the jury's still out on flow augmentation's benefits, according to Karl Dreher, Idaho Department of Water Resources director.

A cardinal rule of statistical analysis says that "just because there's a correlation doesn't mean there's a cause and effect relationship," Dreher told the Northwest Power Planning Council during a Thursday presentation. He used as an example, the NASDAQ stock exchange, which has been steadily on the rise through a period of consistent salmon population declines. The trends correlate, Dreher said, but that doesn't mean the NASDAQ's rise has caused the salmon's decline.

"The principal conclusion of the (Idaho) review is that survival data and flow rates used by Muir et al. (1999), despite showing an apparent correlation between flow rates and survival, do not imply a cause and effect relationship between flow and survival of subyearlings and should not be used as a basis to justify flow augmentation," according to the review's executive summary.

"This is primarily because the experimental design did not address other factors that appear to have strongly influenced migration characteristics and survival."

The "Review of Survival, Flow, Temperature, and Migration Data for Hatchery-raised Subyearling Fall Chinook Salmon Above Lower Granite Dam, 1996-1998," was released in September. It was prepared by Dreher, University of Idaho research scientist Christian R. Petrich, Department of Water Resources hydrogeologist Kenneth W. Neely, Department of Fish and Game anadromous fish manager Edward C. Bowles and IDFG research biologist Alan Byrne.

The Idaho review points out that the studies show that the estimated survival of subyearling fall chinook from upriver points of release to Lower Granite Dam can be correlated with three environmental variables: flow, water temperature and turbidity.

The problem, according to the review's conclusion, is that the studies did not measure the survival effects of those variables independently. The Idaho review quotes a recent NMFS document that says "because environmental variables were highly correlated with each other, determining which variable was most important to subyearling fall chinook salmon survival was not possible."

The Idaho document notes a high correlation between survival and the release date of the fall chinook subyearlings monitored for the study. The salmon, hatched at the same time, were raised at Lyons Ferry hatchery and transported above Lower Granite in sequential releases.

Dreher called release dates "by far the strongest correlation in this data set." Survival rates ranged from 50 to 70 percent for earlier releases compared to less than 10 percent for later releases, Dreher said.

"The NMFS experimental design assumed that sequential releases of hatchery-raised fall chinook would not influence survival independent of flow, temperature, and turbidity. The high correlation between time of release and survival makes this assumption questionable," according to the Idaho review.

The Idaho reviewers also said that subyearling migration travel times did not correspond with flow rates, pointing out that the travel times for the first fish from particular releases arriving at Lower Granite were "less at lower flows than at higher flows for most releases."

"These travel times and arrival patterns were contrary to what would be expected if the higher flows resulted in significant improvements in survival," according to the Idaho review. A confounding factor in the NMFS' studies could be the subyearlings' "readiness to migrate," Dreher's group wrote.

"Correlations of flow and temperature with travel time and survival are only meaningful if the groups of fish studied are actively migrating or relatively similar in their state of ‘readiness to migrate.' " read the review.

Dreher said the subyearlings from the same hatch were released over a six-week time span with "apparently little regard for their physiological development."

The Idaho review said that because flow rates, velocity, temperature and turbidity are so closely correlated, the NMFS study cannot properly judge the individual benefits to fish survival that flow components might provide.

"Understanding the effects of individual attributes of flow, particularly the usefulness of flow augmentation to compensate for the effects of reservoir impoundment on these attributes, is fundamental to determining the effectiveness of flow augmentation efforts for increasing survival of subyearling fall chinook salmon."

The review suggested that "additional problems with existing studies must be addressed prior to making conclusions about the efficacy of flow augmentation."

"In summary, this review does not suggest that flow, or the attributes of flow, are unimportant to migration and survival of subyearling fall chinook salmon. However, existing correlations between survival of hatchery-raised, subyearling fall chinook salmon with flow rates and water temperatures do not support the postulation that augmenting mainstem Snake River flows improves subyearling survival," according to the review.

"Flow is good for fish. Nobody argues that," Dreher told the Council. Research consistently shows that survival is better in "good water years."

"That doesn't mean you can create a good water year with flow augmentation," Dreher said.

Dreher said the state is in the process of submitting the review to NMFS Science Center for review and comments. Montana Council member John Etchart asked Dreher if he would also be willing to submit the document to the Independent Scientific Advisory Board, which offers advice to both the Council and NMFS on science issues. Dreher said the state would not object.

"We wouldn't be out talking about this if we couldn't defend it," Dreher said.

The Idaho review's call for more pointed research to sort out issues related to flow and salmon survival lines up with that of the Council. In its recently approved program amendment, the Council cited the "need to get some real high quality, focused research" under way to resolve numerous scientific uncertainties, said Oregon Council member Eric Bloch.

Comments regarding Idaho's review produced by the Fish Passage Center's Michele DeHart agree with the Idaho review's assessment of the correlation between flow, as well as between release timing and water temperature, on salmon survival. But those comments, made at the request of the Fish Passage Advisory Committee's regional fish managers, question the Idaho report's conclusions.

"The authors (of the Idaho review) argue that correlation does not establish causality (a long held statistical analyses principal) and therefore the fact that a correlation exists cannot be used to support the establishment of a flow requirement to increase survival of ESA listed fall chinook," DeHart wrote.

"This is an interesting argument since it is exactly the argument proffered by statisticians employed by tobacco companies in the past. They recognized that a correlation existed between smoking and lung cancer, but they did argue that this did not establish causality.

"Good principals can be used to buttress bad arguments. History has shown us that in circumstances such as smoking and lung cancer, where survival is at , it may be most prudent to take the protective actions on the basis of the correlation," DeHart wrote.

"In the case of protection of an ESA listed fall chinook where survival is at protection on the basis of a documented correlation is the only judicious action available."

"The Dreher analysis however, does establish a strong argument that NMFS should have included, in their draft biological opinion for 2000, a water temperature target as well as a flow target for the summer months in the Snake River. The establishment of a summer flow target by NMFS is the only prudent alternative action available to the NMFS in light of the fact that the fall chinook stocks in the Snake River have decreased to near extinction.

"The facts that, flow, water temperature, turbidity and release date are all co-dependent variables in the data set do not diminish the importance of the flow survival relationship or the basis for establishing a flow target. In fact, the question should be raised by NMFS regarding the establishment of a water temperature criteria, on the basis of this data particularly in regard to the upper Snake River," DeHart wrote.

DeHart's comment's debunked the Dreher contention that there is no flow-travel time correlation for fall chinook. She said that because of the extended time subyearling spend rearing above Lower Granite one would not expect a significant relationship there.

Her comments said that relationship grows as the fish grow and become more active.

"By the time the composite of wild and hatchery subyearling chinook originating above Lower Granite Dam in the years 1997-1999 were passing between McNary and Bonneville dams, they were migrating at speed closer to that of yearling chinook, traversing this lower Columbia reach in 5-10 days on average.

"Subyearling chinook appear to respond to flow once they reach the state of maturation where they are active migrants, as seen by their increasing migration rates as they move down through the hydrosystem. This clearly shows that higher flow targets would further decrease fall chinook travel time in their downstream migration," DeHart wrote.

Link information:
Idaho Department of Water Resources:

by Barry Espenson
Idaho Report Claims Flow Augmentation Unjustified
Columbia Basin Bulletin, November 3, 2000

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