Aquatic Habitat Losses and Gains due to BC Hydro Dams in the Columbia Basin. A Poisson Consulting Ltd. report prepared for Fish and Wildlife Compensation Program

Author: J.L. Thorley

Its primary aims are to (1) summarize the lotic (rivers and streams) and lentic (lakes) habitat lost and in the case of lakes, gained, by inundation due to dam construction, (2) interpret the significance of these aquatic habitat losses and gains in relation to fish use, (3) outline compensation options with costs and (4) identify the habitat types that are priorities for compensation. For completeness, losses and gains within BC‟s Columbia Basin due to inundation associated with the Bonnevile Power Administration‟s (BPA‟s) Libby Dam are also considered.

Over 38,000 km of rivers and streams and over 1180 km 2 of lakes existed in the compensation region prior to construction of the first dam in 1922.

Lotic habitat losses due to inundation by BC Hydro dams exceed 1,450 km if construction lines are included. The losses have all occurred at lower elevations (<1,000 m) and, excluding Libby Dam, over 60 % (400 km) of the large river habitat type has been inundated. Furthermore, the lotic habitat types most affected by dam construction are the richest in terms of number of native fish species as well as the most productive. With regard to lentic habitats, inundation by BC Hydro dams has resulted in the net loss of 29 % of medium lakes (40 km2 ) and when shallow water habitat is included 13 % of low to moderate elevation small lakes (13 km2 ). Although inundation has increased the area of large lakes by 83 % (676 km2 ) the resultant reservoirs act as nutrient sinks. Again, the losses and gains have all occurred at lower elevations.

Over 38,000 km of rivers and streams and over 1180 km 2 of lakes existed in the compensation region prior to construction of the first dam in 1922.

Lotic habitat losses due to inundation by BC Hydro dams exceed 1,450 km if construction lines are included. The losses have all occurred at lower elevations (<1,000 m) and, excluding Libby Dam, over 60 % (400 km) of the large river habitat type has been inundated. Furthermore, the lotic habitat types most affected by dam construction are the richest in terms of number of native fish species as well as the most productive. With regard to lentic habitats, inundation by BC Hydro dams has resulted in the net loss of 29 % of medium lakes (40 km2 ) and when shallow water habitat is included 13 % of low to moderate elevation small lakes (13 km2 ). Although inundation has increased the area of large lakes by 83 % (676 km2 ) the resultant reservoirs act as nutrient sinks. Again, the losses and gains have all occurred at lower elevations.