Oldman River Basin - Water Supply Forecasts

As of April 1, 2007, average natural runoff volumes are forecast for the March to September 2007 period for the Oldman, Waterton, Belly, and St. Mary Rivers, (Table 4a). Current forecasted values for the March to September 2007 period for the Oldman River at Lethbridge would rank 48th lowest in 91-years of record (1912-2001). Current natural runoff volume forecasts range from 96 to 99% of average. In comparison to March 1 forecasts, this represents an increase of 1 to 3% of average. The March to September 2007 forecast volumes are 1 to 6% higher than those recorded during the same period last year for the Belly, Waterton and St. Mary Rivers, and 7 to 14% higher than last year for the Oldman River at Lethbridge and Brocket.

The first month of the forecast period has been completed, with March 2007 recorded natural runoff volumes ranging from 177 to 229% of average. This is as a result of snowmelt starting about three weeks earlier than normal. Recorded volume data is preliminary, due to ice effects, and is subject to change. March volumes typically comprise a small portion of the March to September total. The remaining volume forecast, which is the March to September 2007 forecast minus the recorded volume to date, is available in Table 4b. The forecast is for below average to average April to September 2007 natural runoff volumes.