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Dry conditions over the past week have helped ease flows in the Winnipeg River basin, particularly in the headwaters where tributary flows remain well above normal for this time of year. The dry and warm weather is expected to persist until Sunday, after which a shift in the weather pattern is forecast. A low pressure system will move across the region on Monday, bringing significant moisture in the form of widespread precipitation and embedded thunderstorms. Although the exact track of the system is still uncertain, the rain is expected to linger for a couple days and be heavy at times.
This precipitation will halt the declining flows and cause inflows to the major lakes to increase over the coming week. Although both Lake of the Woods and Lac Seul are still refilling, continued gradual outflow increases are required to slow the rate of lake level rise. The LWCB is monitoring conditions closely and using the adopted Regulation Strategy to guide operations in consideration of the various interests across the basin.
The current level of Lake of the Woods is 322.73 m (1058.8 ft), a 50th percentile level, within the normal range for this time of year. The average lake level increased by 7 cm (2.8 in) over the past week and is expected to increase by 8 to 15 cm (3 to 6 in) over the next week. Lake of the Woods authorized outflow will increase to:
Each of these flow increases will cause the level of the Winnipeg River to increase, with a total level rise of approximately 32 cm (13 in) directly downstream of the Norman Dam and 17 cm (7 in) above the Dalles. The level at Minaki will not be affected by this flow change.
The current level of Lac Seul is 355.26 m (1165.5 ft), a 60th percentile level, within the normal range for this time of year. The lake level increased by 23 cm (9 in) over the last week and is expected to increase by 18 to 25 cm (7 to 10 in) over the next week. Lac Seul authorized outflow will increase to:
The LWCB Basin Data page will not be updated on Monday, May 18th (Victoria Day in Canada). Daily data updates and publication will resume on Tuesday, May 19th.
Lac Seul is refilling quickly and to manage level rise while inflow to the lake continues to climb, an outflow increase to 250 m3/s is scheduled for Tuesday, May 12th.
Flows in the eastern headwaters of the basin continue to rise and are now well above normal for early May. Dry weather over the past few days has provided some relief, and water levels in the upper tributaries are expected to peak over the weekend. As this large volume of water moves through the system, inflows to the major downstream lakes continue to increase.
At Lac Seul, refill is progressing rapidly, with lake levels now within the normal range. At Lake of the Woods, inflows are expected to rise gradually throughout the week. While local inflows are declining due to dry conditions, operators at Rainy Lake are making significant outflow increases to pass water arriving from the headwaters. To manage Lake of the Woods level rise, additional staggered outflow increases are required.
The current level of Lake of the Woods is 322.66 m (1058.6 ft), a 45th percentile level, within the normal range for this time of year. The average lake level increased by 6.5 cm (2.6 in) over the past week and is expected to increase by 4 to 5 cm (1.5 to 2 in) over the next week. Lake of the Woods authorized outflow will increase to:
Each of these flow increases will cause the level of the Winnipeg River to increase, with a total level rise of approximately 33 cm (13 in) directly downstream of the Norman Dam and 15 cm (6 in) above the Dalles. The level at Minaki will not be affected by this flow change.
The current level of Lac Seul is 355.03 m (1164.8 ft), a 50th percentile level, within the normal range for this time of year. The lake level increased 25 cm (10 in) over the last week and is expected to increase by 18 to 22 cm (7 to 8.5 in) over the next week. Lac Seul authorized outflow is 175 m3/s. An update on the next outflow increase will be provided early next week.
The spring freshet is in full swing across the Winnipeg River basin. Areas to the east, which saw exceptionally high rainfall at the end of April, continue to see rising flows in tributary rivers and inflows to major lakes.
In the Lac Seul sub-basin, flows have risen sharply to high seasonal levels in the east of the basin, including into Lake St. Joseph and in the natural tributaries to Lac Seul east of Sioux Lookout (Sturgeon River, English River). Lac Seul level is projected to rise above the minimum fisheries target for May 15 with this strong freshet response.
Lac Seul authorized outflow will be increased from 100 to 175 m³/s on Tuesday, May 5.
In the Lake of the Woods sub-basin, rainfall at the end of April was heaviest in the eastern headwater regions in Minnesota and Ontario. Flows measured in the major tributaries from these headwaters (Namakan River at the outlet of Lac la Croix and Seine River, respectively), are exceptionally high for early May. Flows in Turtle River in Ontario, another important tributary draining the north of the Rainy basin into Rainy Lake is moderately high. Dam operators at Namakan Lake and Rainy Lake are increasing outflows as this water makes it way through the system, which will result in rising inflows to Lake of the Woods over the next week.
In keeping with the LWCB’s adopted spring Regulation Strategy, Lake of the Woods authorized outflow will be increased from 225 to 275 m³/s on Tuesday, May 5 and from 275 m³/s to 325 m³/s on Friday, May 8. The Winnipeg River level below Norman Dam is expected to rise by 10 cm (4 inches) following each of these outflow increases. The Winnipeg River level at Minaki will not be affected by these flow changes.
