Bow River Basin - Water Supply Forecasts

Below-average natural runoff volumes are forecast for the March to September 2003 period in the Bow River basin (Table 4a). Current forecasts range from 66 to 89% of average for this time of year. The May 1 forecasts are higher (by 1 to 9%) than last month's forecasts due to above-normal precipitation in the basin during April. Forecasts for Banff, Calgary, and the Cascade Reservoir improved the most because the large storm in late April brought the greatest precipitation to these northern parts of the Bow River basin. Forecast volumes for the Highwood, Elbow, and Kananaskis Rivers are slightly better than for the rest of the Bow River basin, because of better soil moisture conditions. Current March to September 2003 volume forecasts are lower than runoff volumes recorded last year for this period, except at Banff where the same volume is forecast. Forecasted volumes are much higher than those recorded in 2001. Current forecasted volumes for the March to September 2003 period for the Bow River at Calgary would rank 22nd lowest in 85-years of record (1912-95).

The first two months of the forecast period are completed, with March-April 2003 recorded runoff volumes ranging from 97 to 133% of average. The remaining volume forecast, which is the March to September 2003 forecast minus the recorded volume to date, is available in Table 4b.