Oldman River Basin - Water Supply Forecasts

As of August 1, 2006, natural runoff volumes for the March to September 2006 period are forecast to be below average for the Oldman Reservoir, below average to average for Lethbridge and the Belly River, and 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 39th lowest in 91-years of record (1912-2001). Current natural runoff volume forecasts range from 84 to 101% of average. In comparison to July 1 forecasts, this represents a decrease of 5 to 8% of average. The March to September 2006 forecast volumes are 6 to 19% higher than those recorded during the same period last year for the Belly, Waterton and St. Mary Rivers, and 17 to 48% lower than last year at Lethbridge and Brocket, where flooding was more prevalent.

The first five months of the forecast period have been completed, with March-July 2006 recorded natural runoff volumes ranging from 84 to 102% of average. Runoff was average, except below 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. Below average to average natural runoff volumes are forecast for the August - September 2006 period, except at the Waterton Reservoir, where average inflows are forecast. Current forecasted value for the Oldman River at Lethbridge would rank 39th lowest in 91-years of record (1912-2001).