Conditions in the Winnipeg River basin are beginning to change quickly. The basin has received larger amounts of precipitation over the past week and over the weekend. Most of the basin received a 7-day total of 25 mm with some areas totaling up to 40 mm.
A low pressure system is forecast to impact the Winnipeg River basin starting this evening, bringing heavy rainfall over the next couple of days. Environment Canada has issued a Rainfall Warning covering the entire basin. This system could bring up to 80 mm (3 in) of rainfall tonight through tomorrow. Forecasts indicate weekly totals could exceed 150 mm (6 in).
This large amount of rainfall will cause flows in tributaries and inflows to the major lakes to rise quickly. Although outflow increases are being made in advance of the upcoming precipitation at Namakan Lake, Rainy Lake and Lake of the Woods, outflows are lower than the expected inflows. Therefore, lake levels will rise and additional, larger outflow increases will be required at Lake of the Woods and may be required at Lac Seul. These outflow increase will be made in consideration of downstream impacts, but levels along the English and Winnipeg Rivers are expected to rise considerably over the next week.
The current level of Lake of the Woods is 322.72 m (1058.79 ft), a 40th percentile level, within the normal range for this time of year. The average lake level increased by 6 cm (2.5 in) over the last week and is expected to increase by 15 to 35 cm (6 to 14 in) over the next week, depending on precipitation amounts. Lake of the Woods authorized outflow is 200 m3/s with planned outflow increases to 225 m3/s today May 21st, 300 m3/s Wednesday May 22nd, and 400 m3/s Thursday May 23rd. More outflow increases may be required depending on the severity of the rainfall over the next couple of days.
Flow changes this week will cause a large and rapid increase in levels along the Winnipeg River. By Friday, water levels will have increased by approximately 40 cm, (16 in) directly downstream of the Norman Dam and by 16 cm (6 in) above the Dalles. The level at Minaki will not be affected by these flow changes, but could increase due to local inflow.
The current level of Lac Seul is 355.2 m (1165.4 ft), a 40th percentile level, within the normal range for this time of year. The average lake level increased by 13 cm (5 in) over the past week and is expected to increase by 30 to 46 cm (12 to 18 in) over the next week. Lac Seul authorized outflow is 150 m3/s with a planned increase to 200 m3/s Wednesday May 22nd.
If you have any questions, comments or observations, please contact the Secretariat at secretariat@lwcb.ca or by calling 1-800-661-5922. This Noticeboard will be updated regularly as conditions develop.
Lake of the Woods Secretariat Notice Board Updates for 05/21/2024 (campaign-archive.com)