1Institute of Ocean Sciences, Sidney, British Columbia, Canada
2University of British Columbia, Vancouver, British Columbia, Canada
3Cultus Lake Laboratory, Cultus Lake, British Columbia, Canada
4University of Victoria, Victoria, British Columbia, Canada
In order to predict the potential mortality of sockeye salmon en route to their spawning grounds, ten-day flow and temperature forecasts were issued for the mainstem Fraser and Thompson Rivers during the period of July 3 to September 11, 1997. These forecasts were issued twice a week using 1) kinematic wave, and simple heat budget models; 2) weather forecasts and recent observations; and 3) recent river temperatures and flows. More extensive flow and temperature measurements were collected at other sites throughout the watershed and these permitted a thorough post-season analysis of the predictive performance. Over the twenty-one prediction periods, root mean square differences between the observed and predicted temperatures at sites on the lower Fraser and lower Thompson Rivers were both $0.88^\circ$ C. Analogous percentage differences between the observed and predicted flows were approximately $16\%$ and $13\%$ respectively. Brief descriptions of the models, the predictive system, and future plans will be given.
Although river temperatures were generally below average in 1997, heavy rains led to much stronger river discharges and significant in-river salmon mortality. At one point in mid-July, flows in the lower and upper Fraser River were respectively 60\% and 100\% larger than normal for that time of the year.