BPA Fish and Wildlife FY 1997 Proposal
Section 1. Administrative
Section 2. Narrative
Section 3. Budget
see CBFWA and BPA funding recommendations
Title of project
Dworshak Dam Impacts Assessment
BPA project number 8709900
Business name of agency, institution or organization requesting funding
Sponsor type ID-State/Local Agency
Proposal contact person or principal investigator
|Mailing address||Idaho Department of Fish and Game
2750 Kathleen Avenue
Coeur d'Alene, ID 83814
BPA technical contact Charlie Craig, EWP 503/230-3430
Biological opinion ID None
NWPPC Program number 10.3C.1, 10.3C.2, 10.3C.3
Project is to optimize the resident fishery of the reservoir which is severely limited by entrainment losses. Our objective is to limit loses to keep kokanee densities at 30 -50 adult fish/ha. Project explores ways to avoid losses using selective water withdrawal or behavioral devices. Project is developing reservoir resident fish loss assessments due to the operation of Dworshak Dam.
Project start year 1987 End year 2001
Start of operation and/or maintenance 1999
Project development phase Maintenance
This project is a partnership developed with the Nez Perce Tribe. They have a “sister” project, # 8740700, addressing item 10.3C.4 in the Council’s program.
An entire run of B strain steelhead and chinook were lost with the construction of Dworshak Dam in 1973. In 1987 to 1991 project identified entrainment losses as driving kokanee populations and destabilizing kokanee fishery. In 1991 to 1994 project reviewed options for the reservoir under the SOR. In 1993 and 1994 we used selective withdrawal to minimize kokanee losses in low water years. In 1995 selective withdrawal and changes in discharge timing were utilized and achieved record high numbers of kokanee in a normal water year. In 1996 entrainment and selector gate settings will be tested in a wetter year. In the future, project results will be used to develop biological and integrated rule curves. The project will also be instrumental in developing resident fish losses assessments.
Biological results achieved
From 1981 to 1992 Dworshak kokanee abundance varied between 5 and 30 adult kokanee/ha. Utilizing selective withdrawal and changes in discharge timing resulted in record high numbers of kokanee; 70 kokanee/ha in 1994 and 80 kokanee/ha in 1995. Kokanee fishery has increased markedly to a total harvest of 150,000 to 200,000 fish annually. Early research findings showed entrainment losses were driving the kokanee population and that in turn was driving the fishery. Research also showed the kokanee fishery would be maximized at densities of 30 to 50 adults/ha.
Annual reports and technical papers
Annual progress reports were published by BPA since 1987.
Showing that entrainment losses can be controlled would be a major research finding which could benefit fisheries on several northwest reservoirs; Dworshak, Libby, and Roosevelt. Locally, keeping kokanee densities up in Dworshak Reservoir provides about 35,000 fishing trips annually which benefits the Orofino commerce (a community struggling with a depressed timber economy).
Dworshak Reservoir is drawndown about 80 feet annually to provide water for anadromous fish flows. Providing a good resident fishery will show that providing anadromous flows are not inconsistent with maintaining a good resident fishery. Minimizing kokanee losses will likely minimize losses of other resident fish species as well. Early years of project demonstrated that it will have no negative effect on native resident fish species.
Specific measureable objectives
To reduce the entrainment losses of kokanee so that densities of 30-50 adult kokanee/ha can be maintained on an annual basis .
To design rule curves for dam operation which include methods to minimize entrainment losses.
To utilize selective water withdrawal to avoid kokanee losses without impacting reservoir productivity as measured by fish growth.
Selective water withdrawal can be utilized to minimize kokanee entrainment losses and significantly increase kokanee densities in the reservoir.
Underlying assumptions or critical constraints
Our assumption is that kokanee entrainment losses will continue to be the limiting factor on this population.
a. Depth distribution of kokanee in front of the dam will continue to be monitored during the day and at night using split-beam hydroacoustics. Recommendations will be made to the Army Corps on where to selectively withdraw water to avoid the depths utilized by kokanee. Population in the entire reservoir will be monitored for significant changes by Hauser type mid-water trawling. Trawling is conducted by a stratified random design. Normal statistics will be applied to determine significant changes in population estimates.
b. Selector gates will be position above, below, and at the same depth as the kokanee layer. Kokanee entrainment rates will be determined utilizing fixed location split beam hydroacoustics.
Brief schedule of activities
Nine transects have been established in front of Dworshak Dam. These will be surveyed by hydroacoustics during spring, summer, fall and winter, both during the day and at night. Temperature profiles will be measured near the dam during each survey. The entire 54 mile long reservoir will be surveyed at 2 mile intervals, at night, from the dam to the headwaters utilizing hydroacoustics. Four of these surveys will be conducted in 1997 to determine movements of kokanee throughout the reservoir. Fixed location hydroacoustics will be used to monitor entrainment losses during tests of selective water withdrawal during the winter of 1996-97. Kokanee abundance in the entire reservoir will be estimated using mid-water trawling in July. Eighteen trawls will be conducted in three reservoir sections to estimate the kokanee population. Spawning counts will be conducted on 3 tributary streams during September as a relative index of kokanee spawner abundance.
Kokanee are potentially the best fish at providing a fishery in highly fluctuating reservoirs. Their one big weakness is that they are highly entrainable through dam structures. If this weakness could be solved, fisheries of over 200,000 fish in the harvest could be maintained on Dworshak Reservoir and other reservoirs in the Columbia drainage.
How to prevent massive entrainment losses of year classes of kokanee.
Summary of expected outcome
The following items will be achieved:
A quality fishery for anglers which have lost a major salmon and steelhead fishery.
Knowledge of how kokanee losses through dams can be avoided.
Knowledge of the distribution of kokanee in a reservoir and near dam structures.
How to maintain resident fisheries in spite of withdrawals of water for anadromous fish.
An improved kokanee population will provide forage for bull trout, large cutthroat trout, and smallmouth bass.
Dependencies/opportunities for cooperation
The project has been done with the cooperation of the Nez Perce Tribe.
There are potential risks to boats and personnel by operating at night on a large reservoir known for having many floating logs and debris.
Trawling will measure kokanee abundance. Spawner counts will substantiate trawling and measure adult kokanee abundance. Creel surveys will measure the fishery.
|Historic costs||FY 1996 budget data*||Current and future funding needs|
* For most projects, Authorized is the amount recommended by CBFWA and the Council. Planned is amount currently allocated. Contracted is the amount obligated to date of printout.
CBFWA funding review group Resident Fish
Recommendation Tier 1 - fund
Recommended funding level $167,300
BPA 1997 authorized budget (approved start-of-year budget) $167,300