Oldman River Basin - Water Supply Forecasts

Below-average natural runoff volumes are forecast for the March to September 2003 period in the Oldman River basin, ranging from 76 to 82% of average (Table 3a). Current forecasts are similar to last month's for southern sub-basins (Waterton, Belly, and St.Mary), while forecasted runoff from northern sub-basins rose by 9% of average since April 1. The March to September 2003 forecast volumes are 12 to 34% higher than those recorded in the same period in 2001 and are just over half the volumes recorded last year. Current forecasted values for the March to September 2003 period for the Oldman River at Lethbridge would rank 20th lowest in 85 years of record (1912-95).

The first two months of the forecast period have been completed, with March-April 2003 recorded runoff volumes ranging from 107 to 139 % of average. The remaining volume forecast, which is the March to September 2003 forecast minus the recorded volume to date, is available in Table 3b.