BC Hydro has received a number of questions about what the propose Grohman Narrows channel improvement project would mean for Kootenay Lake levels. I am pleased to have the opportunity to clarify this issue.
The main driver for the project is the ability to better manage reservoir operations and peak flood levels on Kootenay Lake. Grohman Narrows acts as a constriction, limiting releases from Kootenay Lake, especially during the spring runoff season, and this adds to the flooding potential for the whole system. Relaxing the constriction will not empty Kootenay Lake or cause major impacts downstream because the Corra Linn Dam is still able to control lake levels. FortisBC operates the dam and, with BC Hydro (Kootenay Canal), maintains normal seasonal water levels relatively high to maximize power generation.
If the project goes ahead, there will be no change in lake levels from early summer until late winter. This means that the lake level would still reach 531.8 metres (1,745 feet) on a regular basis, and could also reach levels between 533.4 and 534.6 metres (1,750 and 1,754 feet) or higher during flood events. The only changes would be to freshet peak levels in the spring, which would be reduced by anywhere from 0.2 to two feet, depending on runoff conditions and the amount excavated; and to minimum lake levels in the spring just prior to freshet rise, which would generally be approximately 30 cm (one foot) lower than is typically observed now.
Again, thank you for the opportunity to address this issue.
Mary Anne Coules, BC Hydro Community Relations