Oldman River Basin - Water Supply Forecasts

As of July 1, 2006, natural runoff volumes for the March to September 2006 period are forecast to be average for Lethbridge and the Belly River, below average to average for the Oldman Reservoir, and average to above average for the Waterton and St. Mary Rivers (Table 4a). Current forecasted values for the March to September 2006 period for the Oldman River at Lethbridge would rank 47th lowest in 91-years of record (1912-2001). Current natural runoff volume forecasts range from 89 to 108% of average. In comparison to June 1 forecasts, this represents an increase of 7 to 11% of average in the Belly, Waterton and St. Mary Rivers, and a decrease of 7% at the Oldman River at Brocket, which results in no change for Lethbridge. The March to September 2006 forecast volumes are 11 to 27% higher than those recorded during the same period last year for the Belly, Waterton and St. Mary Rivers, and 11 to 43% lower than last year at Lethbridge and Brocket, where flooding was more prevalent.

The first four months of the forecast period have been completed, with March-June 2006 recorded natural runoff volumes ranging from 90 to 111% of average. Runoff was above average in the Waterton River, average in the Belly and St.Mary Rivers and at Lethbridge, and below average to average at the Oldman Reservoir. Recorded volume data is preliminary, and is subject to change. The remaining volume forecast, which is the March to September 2006 forecast minus the recorded volume to date, is available in Table 4b. Average natural runoff volumes are forecast for the July - September 2006 period. Current forecasted values for the Oldman River at Lethbridge would rank 44th lowest in 91-years of record (1912-2001).