Benefits to Salmon from Destroying the Reservoir Ecosystems

Environmentalists hate reservoirs, focusing on the loss of habitat when the reservoirs were flooded. But new habitat is created, which is, in essence, quite similar to habitat in a natural lake. As a Canadian official involved in hydropower development in Quebec put it: “People think the reservoir is a liquid desert. Nobody ever says that about a lake. If you propose draining a lake, environmentalists would say that would cause a shocking loss of valuable habitat. But if you propose making a reservoir, which is a lake, they say the reverse.”28

Profound effects on salmon, both positive and negative, would arise from a natural-river drawdown. The most significant negative effect of a natural-river drawdown would be to remove three points at which most juvenile Snake River salmon are collected and transported downstream: Lower Granite, Little Goose, and Lower Monumental Dams. If the water no longer flows through bypass and collection systems, the salmon can no longer be transported. And the barges carrying salmon could not longer make it down the river.

The Snake River Salmon Recovery Team observed that “the drawdown alternatives are highly uncertain, and even the most optimistic juvenile passage assumptions associated with a four pool drawdown fail to improve survival values of Snake River stocks beyond what is achievable with juvenile transportation”.29 Computer modeling suggests that the reduced survival associated with reduced transportation would offset all positive effects of drawdown, because “[e]ven drawdowns to a natural river do not give survivals equal to current levels”.30

The original motive for drawdown was to avoid “lethal slackwater pools”. When the first data showing high reservoir survival became available in 1993 and 1994, NMFS researchers warned the NMFS Regional Director, Will Stelle, Jr., that reservoir survival was already so high that drawdown did not seem to be a useful tool for generating more salmon.31 He ignored them.

Given consistent evidence of high reservoir survival, most drawdown advocates now stress increases in river velocity as the primary benefit to drawdown. They blithely skip over the premises that that water particle travel time is a surrogate for fish travel time, and that reducing fish travel time increases survival.

Drs. Chapman and Giorgi suggest that removal of the four lower Snake Dams would decrease juvenile travel time by about 13%,32 but this estimate is based on Raymond’s 1979 paper, which erroneously assumed that the time sample groups were released had no effect on travel time. Even so, they conclude that “we consider the gain from dam removal as modest at best” and warn that “[n]o one should expect a quick fix from dam removal”.33 The U.S. Army Corps of Engineers has reported that the travel time of spring chinook would be reduced by eight to fifteen days, depending on the amount of natural flow.34

The travel time for adult salmon would be increased, probably by 10-30%, because of the increased water velocity.35 No one has bothered to try and figure out whether adverse effects on adults would outweigh benefits believed to accrue to juveniles. One of the most important pieces of computer modeling that has yet to be completed is the upstream passage model which will permit policymakers to balance positive effects on juveniles against negative effects on adults. Without increased funding, such a model will not be completed any time soon. Until the model is available, policymakers have no quantitative basis for assessing the effects of structural or operational changes to the dams.

Under drawdown, the predators in the existing reservoir could actually be “concentrated . . . in the relatively small channel volume”.36 This could increase the “mortality per mile” suffered by the juvenile population as it moves downstream, thus offsetting any supposed gains from speeding the juveniles through those river miles. In addition, salmon predators could lose alternate prey, such as crayfish, and could increase their attention on juvenile salmon, at least until the new environment was formed.37

The Northwest Power Planning Council’s Independent Science Group has also warned that drawdowns could drive non-native fish, like shad, from mainstem habitats into tributaries. “The result could be temporary if not permanently increased interaction between wild salmonids and non-native fishes in tributary environments that have so far remained mostly free of dominance by non-native fishes.”38

Major transition effects would occur. Not only would passage facilities fail to operate as planned, forcing more fish through turbines, but turbine efficiencies would fall, and total dissolved gas supersaturation levels would rise. And because of the more than 20 years of siltation since the reservoirs filled, there could be possibly lethal levels of sediment in the river during the entire decommissioning process.39

Following "normative" demands for high spring flows could have negative effects on salmon in the Columbia River Basin. As explained in Chapter 1, the single largest source of mortality to salmon eggs in the spawning grounds is floods. The Independent Science Group has not attempted to explain how manipulating reservoirs to provide “scouring flows” for salmon would not wipe out the salmon redds.

And since no one is talking about removing many dams downstream, like Bonneville Dam (since that is where large numbers of urban voters live), most of the sediment that is “scoured out” won’t be able to get to the sea, but will get stuck at the next dam down. Some biologists, like John Pizzimenti of Harza Consultants, worry that the sediments contain pollutants that ought to be left alone.

Another negative effect is the loss of rearing habitat for endangered Snake River fall chinook and other fall chinook, like the healthy runs in the Hanford reach. Because fall chinook feed as they migrate downstream, they may have a comparative advantage in the Columbia and Snake reservoirs, which tend to have higher levels of food than the free-flowing rivers would.

Drawdown proponents claim this effect would be overshadowed by an increase in the spawning habitat for adult fall chinook, but no data are available to confirm whether spawning in "natural rivers” would be greater or lesser than in reservoirs. There is substantial evidence that fall chinook now spawn in reservoirs, particularly in the tailraces of the dams. This phenomenon was discovered accidentally when chinook eggs and fry showed up while the Corps of Engineers was dredging the tailrace of Lower Monumental Dam; subsequent surveys have confirmed tailrace spawning in the Lower Granite and Little Goose tailrace areas.40 Drs. Chapman and Giorgi concluded in 1994 that “[e]very time we look for tailrace spawning we seem to find it”.41 The Northwest Power Planning Council’s Return to the River push for drawdown asserts that “[m]ost fall chinook populations spawning in the mainstem reaches of the Columbia and Snake River have been driven extinct”,42 but the Independent Science Group does not consider the significance of tailrace and other reservoir spawning.43

The most dramatic and immediate effect of the drawdowns would be to destroy the ecology that has developed since the reservoirs were filled. Many resident fish species spawn in the reservoir pools and tributaries feeding into the reservoirs, and all this spawning habitat would be lost.44 This, of course, may be counted as an advantage by the salmon partisans.

Nothwithstanding the enormous uncertainty, the Northwest media has begun to build support for drawdown, reiterating the refrain that “the science is now here”.45 In reality, the science has been suppressed nearly out of existence.

28 Gaetan Hayeur, quoted in G. Easterbrook, A Moment on the Earth 339.

29 Quoted in NRC, Upstream 211 (Prepub. ed.).

30 J. Anderson, “Comparison of Mainstem Recovery Options Recover-1 and DFOP”, Dec. 13, 1994, at 1.

31 M. Schiewe, “Preliminary survival estimates for passage of juvenile salmonids through Lower Granite reservoir and Lower Granite dam”, NMFS Internal Memo, Aug. 5, 1994.

32 D. Chapman & A. Giorgi, “Comments on Work of Biological and FCRPS Alternative Work Groups”, at 12 (1994).

33 Id.

34 U.S. Army Corps of Engineers, “Interim Status Report”, at ES-13.

35 U.S. Army Corps of Engineers, “Interim Status Report”, at ES-13.

36 NRC, Upstream 211 (Prepub. ed.).

37 U.S. Army Corps of Engineers, “Interim Status Report”, at ES-13.

38 ISG, Return to the River 151.

39 U.S. Army Corps of Engineers, “Interim Status Report”, at ES-14.

40 U.S. Army Corps of Engineers, “Interim Status Report”, at 9-38.

41 D. Chapman & A. Giorgi, “Comments on NMFS Draft Biological Opinion on FCRPS Operations”, at 11 (1994).

42 ISG, Return to the River 79.

43 Id. at 204 (acknowledging research showing “small groups that spawn in the tailwaters of Snake River dams”).

44 NRC, Upstream 211 (Prepub. ed.).

45 K. Casavant, “New thinking about Columbia salmon”, Jan. 30, 1997.

Previous PageTable Of ContentsNext Page

This Web page was created using a Trial Version of HTML Transit 3.0.