Water Supply Forecast Summary

Water supply conditions continue to improve, as above-normal precipitation this spring has resulted in an increase in forecast runoff from the mountain areas for the third consecutive month. The May 1 natural runoff volume forecasts in the province have increased 3 to 20 % from those produced on February 1. The May 1, 2002 water supply forecast is for much-below-average natural runoff volumes in the Milk River basin, below-average natural runoff volumes in the North Saskatchewan and Red Deer River basins and below-average to average natural runoff volumes in the Oldman and Bow River basins (Table 1).

May 1 forecast volumes increased from last month's forecast in all areas, with the largest increase occurring in the Bow and Oldman River basins. Despite above-average snow accumulations at the higher elevations, the extreme soil moisture deficit and snowpack below 6000 feet being average at most locations are the major reasons for the runoff forecast being below-average to average. The late spring has resulted in very little depletion of the snowpack to date. However, the forecast volumes produced on May 1 are generally 15 to 40% higher than the recorded March to September 2001 natural runoff volumes.

These forecasts assume that precipitation over the summer period will be normal. Precipitation will have a major impact on the summer water supply forecast between now and the end of September. Streamflow volume forecasts will be updated monthly until mid-summer. Check our Forecaster's Comments throughout the month for updated information regarding runoff conditions.

Note: Precipitation from the spring snowstorm that hit southern Alberta in early May was not included in the May 1 forecasts.