ANALYSES OF FLOW MODIFICATION ON WATER-QUALITY IN NECHAKO RIVER

Alcan Smelters & Chemicals Ltd. initiated construction of the final ph ase of the Kemano Completion Project in north-central British Columbia to divert additional water from the Nechako Reservoir to the existing powerhouse. The Nechako Reservoir was created by the construction of the Kenney Dam in Nechako Canyon, a natural barrier to salmon migratio n. The Nechako River downstream of Nechako Canyon supports important r uns of sockeye and chinook salmon. This additional diversion of Nechak o River flow creates the potential of high water temperatures and incr eased thermal stress to migrating sockeye salmon enroute to their spaw ning grounds in Nechako River tributaries. To achieve specific downstr eam water temperature objectives during sockeye salmon migration each summer, a two-level outlet facility adjacent to Kenney Dam is to be co nstructed to release cooling water at 10 degrees C to the Nechako Rive r. Results of mathematical modelling of Nechako River water temperatur es show that, based on specified design criteria, a maximum Kenney Dam release of 167 m(3)/s at 10 degrees C would be required to meet the d ownstream water temperature objectives.