Predictability of the Consequences of the Kemano Hydroelectric Proposal for Natural Salmon Populations

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Abstract
The Aluminum Company of Canada, Limited (Alcan) has proposed completion of its hydroelectric developments to increase aluminum smelting capacity in north-central B.C. The project was started in 1950 and included the Kenney Dam on the Nechako River in the Fraser catchment area, the creation of the Nechako Reservoir, and the construction of facilities for generating power at the Kemano River on the west coast. Completion of development (Kemano Completion Proposal), at a cost of over $2 billion, would divert 84 percent of the initial mean annual discharge of the Nechako River, and 62 percent of the mean annual discharge of the Nanika River in the Skeena catchment area, to the Kemano River. The proposal offers discharges that are intended to protect Pacific salmon stocks, or, where this is not possible, mitigation of losses. This paper identifies the more obvious effects of abstraction and regulation on salmon populations and their habitat. These include interference with migration of adults, changes in the quality of spawning gravel, imposition of stress on all stages of the fish from high total gas pressures and from alterations in ambient temperature, changes in the composition of the total fish community, changes in the production and availability of food, stranding of fish, weakening or loss of cues for homing, and increased exposure to predation from fish and birds. A major difficulty in trying to relate effects to salmon populations lies in distinguishing fish numbers as determined by habitat effects, from numbers determined by the level of recruitment to the rivers as a result of exploitation by the fishery. Three approaches to the problem are: experimental design of impact assessment, modelling changes of discharge and salmon habitat, and analysis of case histories of regulated discharge. The last seems to be the most instructive per unit of effort required. As an approximation to obtaining replication of treatment effects, and to judge the reliability of prediction of effects of flow regulation, case histories of regulated salmonid rivers were examined. It was found that negative effects outnumbered positive ones, that prediction was usually incorrect, and that, even where flow regulation was implemented with the express intention of increasing numbers of salmonids the results fell short of expectations. On this evidence it appears that the outcome of a development as demanding of water as Kemano Completion is difficult to predict in precise quantitative terms and carries some risk for natural populations.

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