Nutrients

Another industrial interference was added to the already complex and volatile mix in the Kootenay Lake system. In 1967, a dam was constructed on the Duncan, a river that flows into the Lake at its northern end.  The dam disrupted some of the North Arm kokanee spawning habitat, but more importantly, it cut off the vital flow of nutrients into the lake, entombing them in reservoir sediments behind the dam.  Five years later, in 1972, Libby dam was installed across the Kootenay River, at the bottom of its southward loop into Montana.   This dam became the coup de grace for the artificially inflated kokanee fishery.  The long stretch of stagnant water created behind the Libby dam (given the upbeat and acronymic name “Lake Koocanusa”) caused virtually all the nutrients to settle out, not only those from the Cominco plant, but the naturally-derived ones as well. 

 The biological system in the Lake started into freefall.  Kokanee escapement (the number of adult spawners returning to a given location) in the North Arm of the Lake was at over a million in the peak year of 1977; by 1991 it was down to a quarter of a million.  The South Arm stocks, always the most vulnerable of the three, became virtually extinct.

 With support from the fledgeling Columbia Basin Fish and Wildlife Compensation Program, A five-year pilot fertilization project was approved. It was to be the largest lake rehabilitation project ever undertaken anywhere.  A couple of huge fertilizer tanks were mounted on a barge with a pusher tug behind it, and beginning in April of 1992, this bizarre craft, with a mixture of dissolved nitrogen and phosphorous in its tanks, would make a weekly ten-kilometer run down the middle of the lake, dribbling the mixture overboard at a predetermined rate.