Bow River Basin - Water Supply Forecasts

Generally below-average to average natural runoff volumes are forecast for the March to September 2003 period in the Bow River basin, except above-average inflows are expected at Lake Minnewanka (Table 4a). Current forecasts range from 73 to 111% of average for this time of year. The July 1 forecasts for Banff, Spray Lakes, Lake Minnewanka and Calgary improved significantly (by 7 to 20%) since last month's forecasts, due to June runoff being higher than expected in these areas.

Current March to September 2003 volume forecasts for the Elbow, Highwood, and Kananaskis Rivers are approximately 30% lower than runoff volumes recorded last year for this period, 6 to 10% higher at Banff and Lake Minnewanka, and similar at Spray Lakes and Calgary. Forecasted volumes are 21 to 44% higher than those recorded in 2001. Current forecasted volumes for the March to September 2003 period for the Bow River at Calgary would rank 38th lowest in 85-years of record (1912-95).

The first four months of the forecast period are completed, with snowmelt essentially finished for the year. March-June 2003 recorded runoff volumes ranged from 76 to 118% 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.

Note that the historical rankings published in last month's report for the Elbow River were incorrect. The March to September forecast volume should have ranked 33rd lowest in 85 years of record, while the June to September forecast would have ranked 28th. These corrections have been made in the online June report.