The Winnipeg River basin has been experiencing very wet conditions over the last couple months. Large precipitation systems, bringing heavy rainfall, have been impacting the basin every 1 to 2 weeks since mid-May. Over the month of June alone, the headwaters of the Rainy-Namakan basin received the highest amount of rainfall in the last 30 years, and other parts of the basin all ranked in the top half for highest precipitation over the last 30 years. On July 2nd, another such system brought 40 to 75 mm of rain, with the highest amounts over Lake of the Woods and the Rainy-Namakan basin.
These bar charts show the quarter monthly (roughly weekly) precipitation in the Rainy-Namakan and Lake of the Woods Basins. The black line shows the normal precipitation over the last 30 years. The blue bars show the observed precipitation. Since mid-May, many blue bars are much taller than the black line, showing well above average precipitation week after week.
This consistent rainfall has resulted in high tributary flows and high lake inflows. Outflows from the major lakes have been steadily increased to allow the excessive water to make its way downstream. However, because of the sustained rainfall and limits in outflow capacity, lake levels have been steadily rising. At Lake of the Woods, the lake level has increased 0.7 m (2.2 ft) since May 10th. The current level of 323.31 m (1060.7 ft) sits just above the normal range, or at 80th percentile. This means that in the last 30 years, the level of Lake of the Woods was higher than it is today 20% of the time, and lower than it is today 80% of the time. In 2022, on July 2nd, the level of Lake of the Woods was 324.1 m (1063.3 ft), which is 0.8 m (2.6 ft) higher than it is today. Which means the level came up twice as high in 2022 as it has so far this year.
The above plots compare the level of Lake of the Woods in 2022 (left) with 2024 (right).
The current level of Lake of the Woods is 323.31 m (1060.7 ft) , an 80th percentile level, within the normal range for this time of year. The average lake level increased by 7 cm (3 in) over the last week and is expected to increase by 5 to 9 cm (2 to 3.5 in) over the next week, depending on precipitation amounts and upstream flow changes. Lake of the Woods outflow is 1111 m3/s with all sluice gates fully open at the Norman Dam in Kenora. The dams cannot be opened any more and outflow will rise as lake level rises and pushes more water through the dams.
The current level of Lac Seul is 356.24 m (1168.8 ft), a 40th percentile level, within the normal range for this time of year. The average lake level increased by 7 cm (3 in) over the past week and is expected to increase by 3 to 7 cm (1 to 3 in) over the next week. Lac Seul authorized outflow was increased to 350 m3/s Tuesday July 2nd with no additional changes currently scheduled.
2024.07.03 Conditions Update and Outflow Increases – Notice Board (lwcb.ca)