Oldman River Basin - Water Supply Forecasts

As of March 1, 2005, natural runoff volumes for the March to September 2005 period are forecast to be below to much below average (Table 3). Note that the Oldman River near Brocket (Oldman Dam) forecast ranking is a bit higher than the others due to better snowpack in the northern reaches of the basin.

Current forecasted values for the March to September 2005 period for the Oldman River at Lethbridge would rank 18th lowest in 91-years of record (1912-2001). Current natural runoff volume forecasts range from 68 to 77% of average. The March to September 2005 forecast volumes are 1 to 6% higher than those recorded during the same period last year for Lethbridge and Brocket, and 5 to 15% lower than last year for the Belly, Waterton and St. Mary Rivers. The March forecasts are 1 to 7% lower than last month's due to below to much below normal precipitation during February.

Although snowpack in the area was severely depleted in January, future precipitation will heavily influence the March-September forecast runoff due to improved soil moisture conditions. This situation results in a wide range of possibilities. If minimal precipitation occurs during the coming months, near record low volumes are possible. Conversely, above normal precipitation could yet result in average runoff volumes.

Also, reservoirs were able to store some of the early runoff volume in January, and most are currently at above average levels.