News Meetings Dec 2003

Studies to test changes in spill and reservoir operations in 2004

Over the past several weeks a workgroup of action agencies, NOAA, fish and wildlife managers and Council staff have held technical discussions on the feasibility of implementing 2004 summer spill and reservoir tests called for in the Council's mainstem amendments. Issues discussed during these work sessions have included such things as test design, study logistics, performance measures, levels of precision and study costs. Thus far, discussions have focused primarily on summer spill tests in the lower river. Discussions on studies to evaluate changes in reservoir operations are continuing and will be expanded in the coming weeks. This memo attempts to briefly summarize what has been considered and currently concluded regarding possible 2004 summer spill and reservoir studies.

Summer spill tests

Currently there are five summer spill test options being considered. General spill levels and proposed studies for the options are summarized in the table below:

The workgroup has come to the following conclusions:

• A major constraint in conducting summer spill studies is the difficulty of tagging fish later in the season. Warmer water temperatures increase stress on fish that are handled and tagged so tagging fish after early July increases mortality risk and sample bias. Also, as the season progresses fewer and fewer fall chinook juveniles are found in the river making it more difficult to capture sufficient numbers of fish. Summer studies that require handling and tagging juveniles usually ends about July 20 of each year. Thus for 2004 it was assumed that no summer spill studies can be conducted in August.
• Proposed studies for Option 4 have not been submitted. How this option will be evaluated must be determined at a later time. For Option 3, two types of survival studies were considered for 2004 summer spill tests-- 1) systemwide studies and 2) project specific studies (as currently planned for options 1 and 2). Systemwide studies attempt to estimate juvenile survival through the entire hydrosystem or a particular stretch of hydroprojects. Project specific studies attempt to estimate survival past an individual hydroproject. 
• After lengthy discussions and analysis it was established that a systemwide survival study is probably not feasible in 2004. To meet the needed statistical confidence limits, a systemwide study would require many years of study and millions of tagged fish. On the other hand, project specific studies using radio tags are probably doable and could provide project specific survival information.
• While doable, project specific studies carry uncertainties. These uncertainties include: 1) whether or not there are indirect or delayed effects on fish passing through the hydrosystem; 2) whether or not July survivals can fairly represent August survival; 3) whether or not the juvenile sampling bias is significant (radio tags need larger fish); 4) whether or not project specific survivals can reasonably estimate system survival; 5) whether or not radio tags affect fish survival.
• The Corps of Engineers is developing a scoping document to help clarify the assumptions and uncertainties surrounding project specific studies. The scoping document will be soon submitted to and considered in the regional technical forum process.

What this means for possible 2004 summer spill tests

• Under Option 1, the status quo, summer spill studies in 2004 are planned for Ice Harbor, The Dalles and Bonneville dams. These are project specific studies evaluating survival past an individual project. 
• Based on the proposed alternatives and study constraints outlined above, a project survival study at Bonneville Dam under Option 2B is the only other study that can be reasonably implemented in 2004. This is a modified project survival study from the one that is currently being proposed at Bonneville.
• For Option 2A and Option 3 no additional studies to the status quo would be implemented in 2004. Again, study plans have not been submitted for Option 4.
• An alternative to conducting new spill studies could be to update existing passage survival models with the most current project survival information and proceed with the planned 2004 spill studies. Once new survival information becomes available it would also be incorporated into the models. Any change in spill from Bi-Op operations in summer 2004 could be evaluated using models to estimate the effects of the operation on juvenile survival. This could be done with both Option 2A and Option 2B. 
• In order to implement new studies in 2004, tags must be ordered by early January 2004. A decision must be made soon as to whether or not new spill studies will be undertaken so studies can be developed and tags ordered.
• The approximate cost for each new project survival study would be approximately $2 to $3 million.
• How the tests will be funded should be clarified.

Reservoir Operation Studies

Montana Fish, Wildlife and Parks (MFWP) believes that an evaluation of the biological effects of a modified summer draft at Libby and Hungry Horse can be conducted in 2004. Studies to evaluate the effects of changes in reservoir operations on resident are well developed. In general, MFWP proposes to study resident fish populations above and below Libby and Hungry Horse dams by collecting needed physical and biological information and utilizing reservoir and riverine habitat modeling techniques. A proposal to assess biological and physical responses to a modified summer draft has been submitted to the workgroups for consideration.  The CBFWA resident fish committee is preparing to review the proposal. Likewise, Council staff is working with MFWP to facilitate a review of the proposal by the ISRP. 

While upriver studies are fairly well developed, lower river evaluations for a modified summer draft operation have only been briefly discussed. There are several problems with attempting to determine the affects of flow changes on outmigrating fall chinook and it is unclear how these problems will be overcome:

• A system-wide study to estimate changes in survival is probably not feasible.
• The proposed flow changes are so small relative to the total river flow any change in survival may not be measurable.
• If both summer spill and reservoir operations were modified in 2004 it would not be possible to separate the survival effects of each operation.

 
Related link: Oregonian article

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