Red Deer River Basin - Water Supply Forecasts

Recorded March to September 2004 natural runoff volumes in the Red Deer River basin were below average. The natural volume forecasts produced for the Red Deer River basin were within 5.4% of recorded values, on average (Table 5).

Going into last winter, basin soil moisture was below average, and much below average downstream of the Dickson Dam, as last year ended on a very dry note, with July-September 2003 volumes ranging from 5th to 7th lowest on record. Winter snow accumulations ranged from below average to average in the upper elevations, and above average to much above average in the plains. Early melt resulted in average runoff during March, but with little snow left and much below average precipitation during the March-April period, volumes during the March-May period were the tenth lowest on record. Precipitation from May through July was normal, steadily improving soil moisture and runoff during this time. Much above normal precipitation in August, and during September in some areas, resulted in above average runoff for these final two months of the runoff season.

Red Deer River at Dickson Dam

The March to September 2004 recorded natural volume for the Red Deer River at Dickson Dam was below average at 789,000 dam³ or 84% of average and ranks 34th lowest on record (based on the 1912-2001 data) (Table 5). This runoff volume is 14% lower than the volume recorded during the same period last year.

Seven monthly (February to August) natural volume forecasts were produced for Dickson Dam for the March to September period. As illustrated in Figure 16, the forecasted values (brown triangles) were below the recorded March to September 2004 natural volume at Dickson Dam (dark blue line) for all but the first month, February. The initial forecast was for below average runoff due to below average to average snowpack and below average soil moisture. Thirty percent of normal precipitation in February though resulted in lowering of the forecast. From then on, forecasts were fairly consistent as precipitation was near normal. However, 150% of normal precipitation during August raised the final volume total back towards the initial forecast. The recorded volume was within the probable range for six of seven forecasts (all but August) and greater than the reasonable minimum for all seven forecasts.

Forecasts ranged within 1.9% to 7.6% of the recorded volumes, and were on average within 5.2% of the recorded March to September volume. February's forecast was the most accurate, and three of the seven forecasts were within 5% of the recorded value.

Red Deer River at Red Deer

The March to September 2004 recorded natural volume for the Red Deer River at Red Deer was below average at 980,000 dam³ or 74% of average and ranks 29th lowest on record (based on the 1912-2001 data) (Table 5). This runoff volume is 24% lower than the volume recorded during the same period last year.

Seven monthly (February to August) natural volume forecasts were produced for Red Deer for the March to September period. Forecasts dropped steadily through the year as volumes remained low despite normal precipitation. Precipitation in the basin during August of over 150% produced August-September runoff which followed the upper forecast range, and raised the year's total back towards the median forecast (May). As illustrated in Figure 17, the forecasted values (brown triangles) were above the recorded March to September 2004 natural volume at Red Deer (dark blue line) for the first four months and below for the last three months. The recorded volume was within the probable range for six of seven forecasts (all but August) and greater than the reasonable minimum for all seven forecasts.

Forecasts ranged within 2.4% to 10.2% of the recorded volumes, and were on average within 5.6% of the recorded March to September volume. May's forecast was the most accurate, and four of seven forecasts were within five percent accuracy (March to June).