Water Supply Outlook for Alberta

October 2006

Red Deer River Basin - Water Supply Forecasts

Recorded March to September 2006 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 5.8% of recorded values, on average (Table 5).

Going into last winter, rivers flows were high and soils were wet due to extreme summer rain storms and above normal fall precipitation. However, below to much below average winter snow accumulations tempered optimism for this year's runoff, as initial forecasts were for below average natural runoff volumes. Forecasts (and river flows) steadily declined to below to much below average as below normal precipitation continued into the summer. Much below normal precipitation during July resulted in the final forecast (issued August 1) dropping significantly, by 7%, since July normally contributes a large portion of the year's precipitation in central Alberta. Natural runoff volumes for the months of July and August ranged from 8th to 15th lowest on record. Above normal precipitation in August and September helped raise volumes for the year above the final forecasted values, but volumes remained below average for the year. However, soil moisture is near normal and flows are currently above average but receding, as we head into winter.

Red Deer River at Dickson Dam

The March to September 2006 recorded natural volume for the Red Deer River at Dickson Dam was below to much below average at 690,000 dam3 or 74% of average, and ranks 22nd lowest on record (based on the 1912-2001 data) (Table 5). This runoff volume is much lower than the volume recorded during the same period last year due to flooding 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 above the recorded March to September 2006 natural volume at Dickson Dam (dark blue line) for all but the final month, August. The recorded volume was within the probable range and greater than the reasonable minimum for all seven forecasts.

Forecasts ranged within 3.6% to 10.7% of the recorded volumes, and were on average within 6.7% of the recorded March to September volume. The initial (February's) forecast was the least accurate, but forecasts generally improved as time went on.

Red Deer River at Red Deer

The March to September 2006 recorded natural volume for the Red Deer River at Red Deer was below average at 948,000 dam3 or 73% of average and ranks 28th lowest on record (based on the 1912-2001 data) (Table 5). This runoff volume is much lower than the volume recorded during the same period last year due to flooding last year.

Seven monthly (February to August) natural volume forecasts were produced for Red Deer for the March to September period. As illustrated in Figure 17, the forecasted values (brown triangles) were above the recorded March to September 2006 natural volume at Red Deer (dark blue line) for the first five months and below for the last two 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 0.6% to 8.1% of the recorded volumes, and were on average within 5.0% of the recorded March to September volume. July's forecast was the most accurate, and four of seven forecasts were within five percent accuracy (April to July).


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