I . INTRODUCTION 



A. HISTORY 



Libby Dam and Lake Koocanusa are located in northwestern 

 Montana, 219 miles upstream from the confluence of the Kootenai and 

 Columbia rivers and about 17 miles upstream from Libby, Montana. 

 Ihis multiple-;^ urpose hydro-electric project is situated at the top 

 of tlie Columbi,\ River Basin power generating system and is included 

 in the International Water Resource Development Plan for the 

 Columbia River Basin in the United States and Canada. Water re- 

 leased through Libby Dam passes through an additional 16 hydro- 

 electric projects on its way to the Pacific Ocean. The U.S. Army 

 Corps of Engineers constructed the dam and is responsible for the 

 maintenance and operation of the facility. 



The Libby Dam project was authorized for at-site power gener- 

 ation, flood control, and related water uses by the Flood Control 

 Act of 1950, Public Law 516 (U.S. Dep. Army 1971a). Since the 

 reservoir is partially located in Canada, an international treaty 

 between the United States and Canada was a prerequisite to the 

 construction of the project. Initial talks during the early 1950's 

 resulted in no treaty and cancellation of the talks. Later negoti- 

 ations resulted in a treaty signed by both countries in 1964. 



Construction of the project began in 1966 and was completed in 

 1973. Reservoir impoundment was initiated in 1972, full pool was 

 reached in 1974, and powerhouse operations began in 1975. A sur- 

 face area of 46,500 acres (28,850 in the United States and 17,650 

 in Canada) is obtained at full pool with a reservoir length of 90 

 miles (48 in the United States and 42 in Canada), with 229 miles of 

 shoreline (117 in the United States and 107 in Canada) (U.S. Dep. 

 Army 1971a). 



In addition to the 28,850 acres inundated by the reservoir, 

 2,000 acres of habitat were lost due to the relocation of the 

 Burlington Northern (formerly Great Northern) railroad grade, and 

 over 2,100 acres of habitat were lost to the construction of High- 

 way 37 along the east side of the reservoir and the Forest Develop- 

 ment Road along the west side of the reservoir. 



Lake Koocanusa inundated 52.5 miles of habitat associated with 

 two rivers and 48.8 miles of habitat associated with tributary 

 streams. These were riparian and aquatic habitats, including di- 

 verse habitat features such as islands, gravel bars, sloughs, 

 riparian shrubland, and mixed deciduous/conifer riparian areas. 

 Loss of riparian habitat had a large adverse impact on the diverse 

 wildlife communities supported by this habitat type (Carothers 

 1977, Thomas et al. 1980). 



Upland habitats inundated by Lake Koocanusa were primarily 

 timbered with ponderosa pine (Pinus ponderosa) , Douglas-fir 



