Seasonal Natural Flow Volumes Summary

Total natural runoff volumes for the March-August period range from above to much above average in the North Saskatchewan and Red Deer River basins, and most of the Oldman River basin. Despite the wet May and June months, natural runoff volumes in the Milk River basin are below average to average for the year. In the Bow River basin, natural runoff volumes vary from below to much below average in the upper Bow River basin (Bow River at Banff and Spray River), average in Kananaskis and above to much above average in Bow River at Calgary, Elbow River at Bragg Creek and Highwood River at the Mouth (Table A).

Natural runoff volumes in the Milk River basin were below average to average for the March-August period; similar to the lower portion of the Oldman River basin (Oldman River at Brocket, Belly River at Mountainview and Oldman River at Lethbridge). Volumes in the Milk River basin are approximately three-forth of average, ranking around the 35th lowest on record (Table 1). However, much above normal May and June precipitation has resulted in a significant improvement, since March-April natural runoff volumes were less than one-fifth of average runoff volume for that period.

Compared to the Milk River basin, total natural runoff volume in the Oldman River basins was considerably higher, average to above average for the March-August period. The total inflow volume to the Waterton and St. Mary reservoirs were above average for that period, ranking 33rd and 40th highest respectively in 91 years of record. In the rest of the Oldman River basin, the natural runoff volumes for the same period were average. Above normal precipitation during May-June fell in the upper portion of the Oldman basin. This precipitation was high enough to result in above average natural runoff volumes in the Waterton and St. Mary River basins for the March-August period (Table 2). Overall, the natural flow volume for the Oldman River basin is normal for this year’s March through August period.

Natural runoff volumes in the Bow river basins vary from much below average to much above average for the March–August period. Preliminary data indicates that recorded March-August natural runoff volume in the Elbow River at Bragg Creek is the 12th highest in 91 years of record i.e. volume equivalent to 140% of the normal volume, while the inflow volume to Lake Minnewanka and river volumes to the Highwood River at the mouth are 16th and 18th highest records respectively. Natural runoff volumes in the Bow and Spray River basins are below to much below average for the March-August period at approximately 65th highest (27th lowest) on record (May-June's precipitation did not fully reach into the back ranges of the mountains of the Bow River basin). Natural flow volume in the Bow River at Calgary is above average, 30th highest on record; however the Kananaskis River at Nakiska Bridge is 42nd higher (50th lowest) which is equivalent to normal volume for the March-August period (Table 3).

On average, the natural runoff volume in the Red Deer River basin is 135% of the normal runoff volume for the period March – August, which is the second highest recorded percentage value (after Elbow River at Bragg Creek). The preliminary data indicates that natural runoff volume for the March through August period in Red Deer is 19th highest with 91 years of record. Inflow to Dickson Dam is 15th highest on record (Table 4).

Natural runoff volumes for the March through August period in the North Saskatchewan River basin are above average; similar to the Oldman River basins. Runoff volume in the North Saskatchewan River at Edmonton ranks 35th highest (57th lowest) on record (Table 5).

Recorded volume data is preliminary and is subject to change.

The final streamflow volume forecast for this year was produced in August, as volumes after September 1 represent a minor portion of the yearly totals. A year in review report will be published next month. Check our Forecaster's Comments throughout the month for updated information regarding runoff conditions.