Water Supply Outlook for Alberta

May 2007

Oldman River Basin - Water Supply Forecasts

As of May 1, 2007, natural runoff volumes for the March to September 2007 period are forecast to be near average 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 44th lowest in 91-years of record (1912-2001). Current natural runoff volume forecasts range from 92 to 96% of average. In comparison to April 1 forecasts, this represents a decrease of 1 to 4% of average. The March to September 2007 forecast volumes are similar to volumes recorded during the same period last year for all but the Oldman River near Brocket, which is forecast to be 13% higher than last year.

The first two months of the forecast period have been completed, with March-April 2007 recorded natural runoff volumes ranging from 130 to 158% of average, except 95% of average in the Belly River. Runoff was above to much above average in all but the Belly River, where it was average. Recorded volume data is preliminary, and is subject to change. The remaining volume forecast, which is the March to September 2007 forecast minus the recorded volume to date, is available in Table 4b. May to September 2007 natural runoff volumes are forecast to be below average to average at all locations.

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