Water Supply Outlook for Alberta

October 2006

North Saskatchewan River Basin - Water Supply Forecasts

Recorded March to September 2006 natural runoff volume in the North Saskatchewan River basin was average at Lake Abraham, and much-below-average at Edmonton and the Brazeau Reservoir (Table 6). Natural volume forecasts produced for the North Saskatchewan River basin were within 10.4% of recorded values, on average.

Going into last winter, soil moisture was above normal. However, much below average winter snow accumulations tempered optimism for this year's runoff, as initial forecasts were for below average natural runoff volumes. Forecasts for the Bighorn Reservoir rose in May to near normal and again in July to above normal as runoff data indicated there was much more snow in the mountains upstream than measurements had shown. Forecasts (and river flows) at the Brazeau Dam and Edmonton declined in June after below average precipitation during May. Forecasts and river flows at all three locations dropped significantly in August as July natural volumes were second, fourth, and sixteenth lowest on record at Brazeau, Edmonton and Bighorn, respectively. After final forecasts were issued in early August, the dry weather continued the rest of the month and August natural volumes were second lowest on record at Edmonton. Much above normal precipitation in September helped compensate and raised volumes for the year back near the final forecasted values. However, soil moisture is near normal and flows are currently average to above average, but receding, as we head into winter.

North Saskatchewan River at Bighorn Dam (Lake Abraham)

The March to September 2006 recorded natural volume for the North Saskatchewan River at Bighorn Dam was average at 2,166,000 dam3 or 101% of average and ranks 16th lowest in thirty years of record (1973-2001 data) (Table 6). This is 1% lower than the volume recorded during the same period last year.

Seven monthly (February to August) natural volume forecasts were produced for Bighorn Dam for the March to September period. As illustrated in Figure 18, the forecasted values (brown triangles) were below the recorded March to September 2006 natural volume at Bighorn Dam (dark blue line) for the first five months, and slightly above during July and August. The recorded volume was within the forecast probable range and greater than the reasonable minimum for all seven forecasts.

Forecasts ranged within 2.7% to 8.4% of the recorded volumes, and were on average within 5.0% of the recorded March to September volume. The June through August forecasts were the most accurate, within 2.7 to 3.4%, while April's was the worst and the remaining three forecasts were within 5.3 to 6.5% of the recorded value.

Brazeau River at Brazeau Dam

The March to September 2006 recorded natural volume for the Brazeau River at Brazeau Dam was much below average at 898,000 dam3 or 63% of average and ranks lowest in 41 years of record (1962-2001 data) (Table 6). The March to September 2006 recorded volume is 71% lower than the volume recorded over the same time period last year.

Seven monthly (February to August) natural volume forecasts were produced for Brazeau Dam for the March to September period. As illustrated in Figure 19, the forecasted values (brown triangles) were above the recorded March to September 2006 natural volume at Brazeau Dam (dark blue line) for all seven months. The recorded volume was within the forecast probable range and greater than the reasonable minimum for only the August forecast.

Forecasts ranged within 0.2% to 23.8% of the recorded volumes, and were on average within 17.9% of the recorded March to September volume. August's forecast was the most accurate, but none of the other six forecasts were within 17% of the recorded value.

North Saskatchewan River at Edmonton

The March to September 2006 recorded natural volume for the North Saskatchewan River at Edmonton was much-below-average at 4,429,000 dam3 or 76% of average and ranks 12th lowest on record (based on the 1912-2001 data) (Table 6). The 2006 recorded volume is 47% lower than the volume recorded over the same time period last year, when flooding occurred.

Seven monthly (February to August) natural volume forecasts were produced for Edmonton for the March to September period. As illustrated in Figure 20, the forecasted values (brown triangles) were above the recorded March to September 2006 natural volume at Edmonton (dark blue line) for all but August's forecast. The recorded volume was within the probable range for four of seven months (all but May, June, July) and greater than the reasonable minimum for all seven forecasts.

Forecasts ranged within 0.3% to 12.2% of the recorded volumes, and were on average within 8.4% of the recorded March to September volume. August's forecast was the most accurate, with the rest of the forecasts within 8.8 to 12.2% of the recorded value.


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