A precipitation system will impact southern portions of the Winnipeg River basin this Friday, April 21. Snow is expected, with amounts ranging from 10 to 15 cm (4 to 6 in) and in some locations as high as 25 cm (10 in). This precipitation will, in the short term, cause increased flows and levels in the rivers and lakes. In the long-term, this added snowpack will increase the snow water content and as it melts will cause river flows and lake inflows to remain at above normal levels. Additional larger outflow increases are scheduled at Lake of the Woods to help slow the rate of level rise. The ice cover is no longer in place on the Winnipeg River, minimizing the impact of river level rise due to these outflow increases.
The current level of Lake of the Woods is 322.57 m (1058.3 ft), a 50th percentile level for this time of year. The average lake level increased by 14 cm (5 in) over the past week and is expected to increase by 13 to 16 cm (5 to 6 in) over the next week. Lake of the Woods authorized outflow will increase to 575 m3/s on Friday, April 21 (slightly higher than planned) and again to 625 m3/s on Monday, April 24.
Each of these outflow changes will cause levels along the Winnipeg River to increase by 14 cm (5 in) directly below the Norman Dam and by 8 cm (3 in) above the Dalles for a total rise of 28 cm (11 in) and 16 cm (6 in) respectively at each location. These flow changes will not affect the level at Minaki.
Less precipitation is forecast to impact the English River basin on April 21st. In this basin, freshet is slow to begin and river flows and lake inflows are at low-normal conditions. As such, an outflow reduction was scheduled at Lac Seul to allow for the lake level to start rising gradually in anticipation of higher spring inflows.
The current level of Lac Seul is 354.84 m (1164.2 ft), a 50th percentile level for this time of year. The lake level increased by 3 cm (1 in) over the past week and is expected to increase by 6 to 8 cm (2 to 3 in) over the next week. Lac Seul authorized outflow was reduced to 100 m3/s on April 20.