Mountain Water Supply Summary

Due to an extremely wet June in all of the five major water supply forecast basins, forecasts have been discontinued for the rest of this year.

Total natural runoff volumes for the year so far (March - July) range from above average to much above average in the North Saskatchewan and Red Deer River basins, and most of the Bow River basin. Despite the very wet June, natural runoff volumes in the Milk River basin are below to much below average for the year so far due to previous dry months. In the Oldman River basin, natural runoff volumes vary from below to much below average in the south (St. Mary River) to above average in the north (Oldman Reservoir). However, any further precipitation will readily translate into runoff since soil conditions are wetter than they've been in years.

In the North Saskatchewan (Table 1) and Red Deer (Table 2) River basins, preliminary data indicates that natural runoff volumes for the March through July period are among the ten highest in up to 91 years of record.

In the Bow River basin, preliminary data indicates that recorded March - July natural runoff volume in the Highwood River is the fifth highest in 91 years of record, and inflow to Lake Minnewanka is 13th highest. Natural runoff volumes in the Kananaskis and Spray River basins are above average for the March - July period at approximately 32nd highest on record. Since June's heavy precipitation did not fully reach into the back ranges of the mountains of the Bow River basin, the recorded March through July total runoff volume for the Bow River at Banff is below average. Natural flow volume in the Bow River at Calgary is above to much above average, 23rd highest on record (Table 3).

The total inflow volume to the Oldman Reservoir (near Brocket) was above average for the March-July period, ranking 26th highest in 91 years of record. In the southern half of the Oldman River basin, natural runoff volumes for the same period were below average in the Waterton and Belly River basins, and below to much below average in the St. Mary River basin. The heaviest precipitation during June fell to the north of these three southern rivers, and several months previous to June were dry. Flows at Brocket, however, have been high enough to result in average natural runoff volumes in the Oldman River at Lethbridge for the March-July period (Table 4).

Natural runoff volumes in the Milk River basin were below to much below average for the March-July period, similar to the St. Mary River basin in that the heaviest precipitation fell to the north and previous months were dry. Volumes in the Milk River basin are just over half of average, ranking around the 24th lowest on record (Table 5). However, this still represents a dramatic improvement due to June precipitation, since March-May natural runoff volumes were less than a quarter of average.

Recorded volume data is preliminary and is subject to change. Check our Forecaster's Comments throughout the month for updated information regarding runoff conditions.