Salmon: Adaptive Management Over Breaching
by Glen Squires
WHEAT LIFE, April 2002
Adaptive migration, not dam breaching, summarizes the Corp of Engineers' vision for the most effective salmon passage in the lower Snake River. The basis for this vision began in 1995 with the Lower Snake River Juvenile Salmon Migration Feasibility Report / Environmental Impact Statement (FR/EIS). The project focused on the relationship between the four dams on the lower Snake River and their effects on juvenile fish making their way to the ocean.
In response to coordination with National Marine Fisheries Service's (NMFS) Biological Opinions, the Corps offered its recommended plan (preferred alternative) for operating the hydropower projects. The Corps considers implementation of its recommended migration improvements to be a positive step towards meeting NMFS's regional survival and recovery goals for salmon and steelhead species listed under the Endangered Species Act. The FR/EIS was released in February 2002.
A recent summary of the study revealed that a spread-the-risk policy is currently in place, wherein 50-65 percent of all fish traveling through the lower Snake River are diverted and collected for transport around the dams. The rest of the fish are left in the river to migrate. This policy is necessary because the long-term positive and negative effects of both in-river migration and fish transport are unclear. According to the Corps, direct survival of salmon through a dam and reservoir on the lower Snake is in the low 90-percent range. Cumulative survival through four dams is over 80 percent, and cumulative survival for juvenile salmon through all eight dams on the Columbia/Snake River System generally ranges from 45-60 percent. It is the possibility for indirect mortality that continues to puzzle scientists who remain unsure whether the trip downstream affects the number of salmon returning to the river system to ultimately spawn.
Another focus of the summary relative to the adaptive management strategy is the development and implementation of new technologies. These include surface bypass systems that reduce stress on juvenile salmon by keeping fish near the water's surface. Removable spillway weirs also reduce stress by reducing gas supersaturation, increasing fish passage efficiency and reducing the need for spill. Behavioral guidance systems direct fish away from the powerhouse. For those fish that do travel through the dam's turbines, reduced-gap turbine blades, smoother surface materials on turbine parts and changing operational efficiency of the turbines are some of the actions being taken.
Finally, although each Snake River dam currently has spillway "flow deflectors" to prevent deep plunging of the water, the addition of more deflectors and improvements for existing deflectors are scheduled. In its 2000 Biological Opinion, NMFS calls for increase spill along with spillway improvements to facilitate harmful total dissolved gas.
The Corps chose to follow the path of "most certainty," as illustrated by the following summary of key factors supporting the Agency's selection of the "Adaptive Management" option over dam breaching as their recommended plan:
Conversely, "uncertainty" seems to be mostly rooted in the dam breaching alternative, thus ranking it beneath the preferred alternative. The dam breaching option has caused heightened controversy and debate within the region and, essentially, nationwide, even becoming a topic in the presidential campaign. The Corps listed the following as a subset of factors, illustrative of the uncertainty associated with dam breaching:
The general public and numerous interest groups provided extensive input as the Corps considered and studied the many factors associated with salmon and the hydropower system. The accompanying chart illustrates the impacts on the various resources from the alternatives considered for river operation. There is a notable negative effect both in the short term and long term from dam breaching.
The Corps makes reference in their study summary to a bigger picture and that the recommended plan will be folded into the existing processes for consideration and coordination with the Regional recovery efforts. NMFS, the driver behind the "processes," highlighted in their 2000 Biological Opinion that "Although breaching is not essential to implementation of the initial actions called for in the Reasonable and Prudent Alternative (RPA) which constitute a non-breach approach, the RPA requires that the Action Agencies prepare for the possibility that breaching or other hydropower actions could become necessary."
Thus, while breaching dams is not the Corps' preferred alternative for operating the hydro system to benefit salmon, the option is clearly not off the table of consideration.
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