Ecological Knowledge and Environmental Problem-Solving Concepts and Case Studies (1986) / Chapter Skim
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21. Raising the Level of a Subarctic Lake
21. Raising the Level of a Subarctic Lake
Pages 317-330
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From page 317... ...
For these reasons, prediction of the consequences of altering the dimensions of lakes is more difficult and more uncertain than prediction of the responses of lakes to pollutants and their elimination. Southern Indian Lake, in northern Manitoba, was raised 3 m in 1976, and rivers were diverted so that the flow of water through the lake was reduced by about 75%.
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From page 318... ...
Southern Indian Lake supported the largest commercial fishery in northern Manitoba. About 85% of the catch was Coregonus clupeaformis, the lake whitefish.
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From page 319... ...
The limnologists recognized that the diversion scheme would alter flow patterns in the lake and that some regions would be flushed more quickly than others. In their opinion, the altered flow would have a greater impact on water chemistry than would inundation itself, because Churchill River water greatly influenced the main basins of the lake under natural conditions.
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From page 320... ...
The overburden of frozen glaciolacustrine clays around Southern Indian Lake, however, had great potential for erosion. Increased turbidity would negate benefits of increases in nutrients, according to surveys of light penetration and primary productivity.
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From page 321... ...
Early in the study, the federal-provincial study board had identified the need for long-term ecological monitoring of the impact areas. Hecky and his colleagues at the Freshwater Institute initiated their own case study of the Southern Indian Lake reservoir in 1974 with the preimpoundment work.
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From page 322... ...
Genetic markers measured among whitefish stocks before and after impoundment indicate that stocks became redistributed when normal flow patterns were altered. There is an indication of net emigration of whitefish from Southern Indian Lake.
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From page 323... ...
The decline in predation by fish could reflect a decrease in stocks or unsuccessful foraging due to turbidity. The changes in the zooplankton community in Southern Indian Lake parallel some of the changes that occurred in Lake Tahoe when Mysis was introduced (Goldman et al., 1979; Richards et al., 19751.
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From page 324... ...
Hecky and colleagues undertook in 1984 their own retrospective analysis of environmental impact prediction and assessment based on their experience with Southern Indian Lake (Hecky et al., 19841. Scientists who had formulated the original predictions and then used the experiment to advance understanding provided their scientific insights into the limitations and capabilities of the prediction process.
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From page 325... ...
In fact, impoundment levels greater than 3 m would have produced effects only slightly worse than actually occurred, because severe shoreline erosion began as soon as the natural range of water levels was exceeded and the impounded water entered the previously frozen backshore zone. The Freshwater Institute scientists bemoaned the lack of suitable analog studies and the limitations of current reservoir paradigms.
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From page 326... ...
1984. Thermal and optical characteristics of Southern Indian Lake before, during, and after impoundment and Churchill River diversion.
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From page 327... ...
1984. The Southern Indian Lake impoundment and Churchill River diversion.
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From page 328... ...
For a study that encompasses an entire ecosystem, such a common means of presentation of data is necessary. Nonetheless, events in Southern Indian Lake are traceable to the life histories and physiological and behavioral characteristics of individual interacting populations.
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From page 329... ...
If fish predation were substantially relaxed, these species would likely be affected. The professional publications produced as a result of the Southern Indian Lake study are valuable contributions to current knowledge about reservoir processes.
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From page 330... ...
1984. Primary productivity of Southern Indian Lake before, during, and after impoundment and Churchill River Diversion.
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