Mitigation for the Construction and Operation of Libby Dam

INTRODUCTION
Libby Reservoir was created under an International Columbia River Treaty between the
United States and Canada for cooperative water development of the Columbia River Basin
(Columbia River Treaty 1964). Libby Reservoir inundated 109 stream miles of the mainstem
Kootenai River in the United States and Canada, and 40 miles of tributary streams in the U.S.
that provided habitat for spawning, juvenile rearing, and migratory passage (Figure 1). The
authorized purpose of the dam is to provide power (91.5%), flood control (8.3%), and navigation
and other benefits (0.2%; Storm et al. 1982).
The Pacific Northwest Power Act of 1980 recognized possible conflicts stemming from
hydroelectric projects in the northwest and directed Bonneville Power Administration to "protect,
mitigate, and enhance fish and wildlife to the extent affected by the development and operation of
any hydroelectric project of the Columbia River and its tributaries..." (4(h)(10)(A)). Under the Act,
the Northwest Power Planning Council was created and recommendations for a comprehensive fish
and wildlife program were solicited from the region's federal, state, and tribal fish and wildlife
agencies. Among Montana's recommendations was the proposal that research be initiated to
quantify acceptable seasonal minimum pool elevations to maintain or enhance the existing fisheries
(Graham et al. 1982).
Research to determine how operations of Libby Dam affect the reservoir and river fishery
and to suggest ways to lessen these effects began in May, 1983. The framework for the Libby
Reservoir Model (LRMOD) was completed in 1989. Development of Integrated Rule Curves
(IRCs) for Libby Dam operation was completed in 1996 (Marotz et al. 1996). The Libby Reservoir
Model and the IRCs continue to be refined (Marotz et al 1999). Initiation of mitigation projects
such as lake rehabilitation and stream restoration began in 1996. The primary focus of the Libby
Mitigation project now is to restore the fisheries and fisheries habitat in basin streams and lakes.
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