Mitigation, compensation, and future protection for fish populations affected by hydropower development in the upper Columbia system, Montana, U.S.A.

Abstract

Pursuant to the Northwest Power Planning Council's Fish and Wildlife Program for the Columbia River system, we estimated losses in fish populations and developed mitigation, compensation, and protection alternatives for reservoirs and downstream river reaches affected by hydropower development in the Flathead and Kootenai River systems in northwest Montana, U.S.A. The construction of Hungry Horse Dam has resulted in estimated annual losses of 65 500 migratory juvenile westslope cutthroat and 1965 adult migratory bull trout from the Flathead Lake and River system. In addition, operations of Hungry Horse and Kerr dams caused annual losses conservatively estimated at 96300 river-spawning and 131 OOO lakeshore-spawning kokanee adults. Water level fluctuations caused by dam operations at Libby and Hungry Horse reservoirs result in: (I) altered thermal stratification, (2) indirect losses in phytoplankton and zooplankton production, (3) direct washout of phytoplankton and zooplankton through dam penstocks, (4) reductions in standing crop of benthic organisms and of insects on the water surface, and ( 5 ) reduced fish growth in the late summer and fall. Mitigative measures include: (1) 99.2 and 113.3 m3 s-' minimum flows in the Flathead and Kootenai rivers respectively, to protect salmonid eggs and juveniles, (2) improvement of fish passage to restore migrations between the Flathead and Swan systems, and (3) biological rule curves for operations at Libby and Hungry Horse reservoirs. To compensate for fisheries losses, we recommend enhancement of spawning and rearing habitat, introductions of hatchery juveniles, and spawning channels. We recommend protection from further hydropower development for lo() stream reaches (13% km) for fish species of special concern, and for outstanding sport fisheries. These and other measures will be considered by various agencies in developing an overall fisheries restoration plan which should be flexible, and employ principles of adaptive management. Effectiveness of the plan may be limited by heavy reliance on hatchery fish. Although mitigation efforts may not restore fish populations to pre-dam levels, substantial benefits should be realized.

Predicting environmental mitigation requirements for hydropower projects through the integration of biophysical and socio-political geographies

“…Operation of a hydropower facility typically involves modifications to hydrologic regimes both upstream and downstream of dams, reservoirs, or river diversions (Fraley et al, 1989;Ligon et al, 1995;Poff et al, 1997). The magnitude of these flow disturbances can be minimized by discharge management, and there is increasing pressure from regulatory agencies to incorporate ecological flow requirements in licenses and operational plans for hydropower projects (Bunn and Arthington, 2002;Renofalt et al, 2010;Trussart et al, 2002).…”

“…The presence or absence of important fish species can influence not only fish passage mitigation requirements but also other measures related to biological conservation (Cada, 1998;Fraley et al, 1989;Renofalt et al, 2010). We used conservation status in concert with expert opinion to compile a list of high profile migratory fish species supported by policy protections (McManamay et al, 2015).…”

“…Where a hydropower project falls on the stream network in relation to other barriers and the network mouth can have a strong influence on the nature and magnitude of ordered mitigation (Fraley et al, 1989;Kosnik, 2010).…”

Libby Mitigation Program, 2007 Annual Progress Report: Mitigation for the Construction and Operation of Libby Dam.

“…The primary focus of the Libby Mitigation project now is to restore the fisheries and fish habitat in basin streams and lakes. (Fraley et al 1989), and then refined in 1996 (Marotz et al 1996). Integrated Rule Curves (IRC's) were adopted by NPPC in 1994, and have recently been implemented, to a large degree, in the federal Biological Opinion (BiOp) for white sturgeon and bull trout (USFWS 2000).…”

Columbia River System Operation Review : Final Environmental Impact Statement, Appendix D: Exhibits.

“…Lake Koocanusa is noted for its kokanee, westslope cutthroat trout, rainbow trout, bull trout, and burbot (Fraley et al, 1989), while the Kootenai River below Libby Dam has an excellent rainbow trout fishery and a sizable whitefish population. Westslope cutthroat trout and bull trout are important sport species in Hungry Horse Reservoir.…”