Mountain Water Supply Forecast Summary

As of August 1, 2004, natural runoff volumes for the August-September period are forecast to be generally below-average in most areas of the Oldman, Bow, Red Deer and North Saskatchewan River basins and much-below-average in the Milk River basin. Exceptions include the Cascade and Bighorn Reservoirs, where average runoff is forecast.

The first five months of the runoff season have finished, comprising 75 to 90% of runoff for the March-September season. Preliminary data as of August 1 indicates March-July natural runoff volumes ranged from below to much-below-average at most forecast locations, except average at the Bighorn and Cascade Reservoirs. March-July volumes generally rank between the tenth and thirtieth lowest in up to 91 years of record.

As of August 1, 2004, Alberta Environment natural runoff volume forecasts for the March through September 2004 period range from below to much-below-average in the Milk, Oldman, Bow, Red Deer and North Saskatchewan River basins, with the exceptions of the Cascade and Bighorn Reservoirs, where average inflow volumes are forecast.

Forecasted March to September 2004 volumes range from 3% higher to 16% lower than those recorded during the same period last year in the North Saskatchewan River basin, 21 to 33% lower in the Milk and Red Deer River basins, 4 to 7% higher in the Bow River basin except at Banff which is 2% lower and the Highwood River which is 11% lower, and 3 to 15% higher in the Oldman River basin except at Brocket, which is 9% lower (Table 1). Changes from July 1 forecasts ranged from a 5% drop for the Oldman River near Brocket to a 10% rise at the Bighorn Reservoir, with forecasts at ten of the twenty locations dropping, seven rising, and three similar to last month.

These forecasts assume that precipitation for the remainder of the forecast period will be normal. Check our Forecaster's Comments throughout the month for updated information regarding runoff conditions.