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 72 to 83% of average (Table 3a). Forecasts for all sub-basins rose substantially, by 6 to 11% of average, due to much-above-normal precipitation in the mountains in March and above-average to much-above-average runoff last month due to the very rapid melting of plains and foothills snowpack. The March to September 2003 forecast volumes are 13 to 26% higher than those recorded in the same period in 2001 and are about half the volumes recorded last year. Current forecasted values for the March to September 2003 period for the Oldman River at Lethbridge would rank 19th lowest in 85 years of record (1912-95).

The first month of the forecast period has been completed, with March 2003 recorded runoff volumes ranging from 117 to 157 % of average due to the quick melting of plains and foothills snowpack. The remaining volume forecast, which is the March to September 2003 forecast minus the recorded volume to date, is available in Table 3b.