< May 2005 Issue

Independent scientists recommend study to observe effects of river flow fluctuations on salmon survival in this low-flow year

Link: Richard Whitney's PowerPoint presentation (220k PDF)

The Council directed its staff to investigate the feasibility of an experiment that would assess the impacts of river flow fluctuations caused by hydropower operations - known as "load following" - on the survival and behavior of migrating juvenile salmon and steelhead. The Independent Scientific Advisory Board (ISAB), which advises the Council, NOAA Fisheries and the Columbia River Inter-Tribal Fish Commission, recommended the experiment.

Columbia and Snake river flows fluctuate with demand for power, and in a low-flow year like 2005 those fluctuations are more pronounced. Hence, 2005 would be a good year to conduct such an experiment, the ISAB reasoned. Scientists generally believe that survival of migrating juvenile salmon and steelhead declines in low flows, but the matter has not been tested through experimentation with different levels of flow.

While it is too late to observe the impacts on juvenile spring Chinook, it is not too late for fall Chinook, Dr. Richard Whitney, an ad-hoc member of the ISAB, told the Council at its Walla Walla meeting. Whitney said the experiment would require cooperation from federal agencies to ensure "rigorous adherence to a predetermined schedule of alternating periods of load-following and no load following." The experiment also would require approval of NOAA Fisheries because of the potential impact on ESA-listed salmon and steelhead.

Most federal agency representatives at the Council meeting said it would be difficult to conduct a test in a low-flow year and agreed with Whitney that it is too late to test flow impacts on spring Chinook. The Council recommended such an experiment in 1994, but it never was conducted - largely because the federal agencies focused on implementing river operations in the 1995 Biological Opinion on Hydropower Operations. Whitney said the experiment could help explain the cause of low fish survival at low flows, thus helping to identify appropriate management measures to address the problem.