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2022.05.23 Lake Level Forecasts

Record flow conditions are occurring across many areas of the Winnipeg River drainage basin in Ontario, Manitoba and Minnesota following record high precipitation since the start of April and early May. Forecasts indicate that inflows to all major lakes will continue to be exceptionally high, but falling, for the 7-day forecast period. Many natural tributaries across the region have crested with some now falling, but it is unlikely that they will return to normal flows this month. Water levels will remain high for at least several weeks across most areas of the basin as a result. Wet weather will prolong the duration of high water levels.

The current level of Lake of the Woods is 323.76 m (1062.2 ft), over 95th percentile level for this time of year. The average lake level rose by 16 cm (6 in) over past week.

The level of Lake of the Woods is above the top of the Legislated Operating Range, 323.47 m (1061.25 ft). The International Lake of the Woods Control Board has been activated and is working with the Canadian Lake of the Woods Control Board to approve any actions taken with respect to Lake of the Woods. Under Canada-US Treaty, upon reaching a lake level of 323.39 m (1061.0 ft), outflow from the lake must be regulated to avoid exceeding a level of 323.85 m (1062.5 ft). The dams in Kenora have been fully opened since the level of the lake was at an elevation of 323.24 m (1060.5 ft). No additional actions can be taken by the Boards to limit the rate of lake rise, which will depend on rainfall over the coming weeks.

Lake of the Woods Legislated Operating Range and Flood Limit

The level of Lake of the Woods is expected to rise by approximately 10-13 cm (4-5 in) over the next 7 days. Inflow is expected to decrease over this period, but still remain greater than the outflow from the fully opened dams. Continued rise beyond the 7-day forecast window is expected. The timing of the peak cannot be predicted at this point and will depend on rainfall. Lake of the Woods water levels will likely remain above the Legislated Operating Range for many weeks. Record lake levels are possible if wet weather returns in the Rainy-Lake of the Woods watershed.

As the lake continues to rise, the level of the Winnipeg River between Kenora and Minaki will also rise. The level rise over the next 7 days below Norman Dam and down to Minaki is expected to be 5-8 cm (2-3 in). This estimate is approximate given uncertainty in the local flows entering the river from tributary areas. The river will continue to gradually rise as long as Lake of the Woods continues to rise and daily fluctuations, up or down, are possible depending on how prevailing winds affect the local level of Lake of the Woods above the dams.

The current level of Lac Seul is 356.43 m (1169.4 ft), over 95th percentile level for this time of year. Lac Seul inflow is extremely high, resulting in a rise of 45 cm (1.5 ft) over the past week. The lake is nearing the Flood Reserve, a range of water levels above the normal operating range defined by federal Order-in-Council that corresponds to a key level for dam safety concern for the Ear Falls dam. To avoid exceeding this range , additional outflow increases took place over the weekend, with outflow now at 810 m³/s. This is a very high outflow, last reached in 2008. The Board has paused further increases pending additional analysis on the risk of reaching the top of the Flood Reserve and a meeting with hydroelectric companies to review dam safety and discuss operational issues related to the record flows along the English and Winnipeg Rivers. Further outflow increases from Lac Seul are possible this week.

Lac Seul Operating Range and Flood Reserve

The LWCB recognizes that downstream areas along the English River, including Pakwash LakeGrassy Narrows, Wabaseemoong, and the Winnipeg River in Manitoba are already experiencing extremely high and damaging water levels, with many areas well above previous records. States of emergency have been declared in several communities with evacuations underway. The Board’s decision to increase flows out of Lac Seul is to address a significant risk of requiring much higher outflows towards the end of May and early June once Lac Seul reaches the top of the Flood Reserve. High outflows from Lac Seul in the near term reduce the risk of extremely high, possibly record-breaking outflows, in the medium term.

These flow increases from Lac Seul will take some time to work down the English River, with an estimate of about two weeks to reach Nutimik Lake.