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LWCB Secretariat Update: 2022.08.04 July Precipitation

LWCB Secretariat Update: 2022.08.04 July Precipitation

Although water levels on the major lakes peaked in June, heavier precipitation over the month of July did cause levels to stall. All areas of the basin received above normal precipitation between July 1st and 30th, even ranking above 80th percentile for all sub-watersheds, as shown in the graph and table below. This was a reversal of conditions compared to the month of June, which saw lower than normal precipitation totals. A significant portion of the basin recorded between 100 and 140 mm of rainfall over the course of the month. Some pockets of very high precipitation, ranging from 150 to 200 mm, were recorded along the Winnipeg River just North of Kenora and in the upper reaches of the Rainy Lake sub-watershed near Atikokan.

Basin Mean Precipitation July 1-31 / Source: Canadian Precipitation Analysis July 1-31 Precipitation Totals for Lake of the Woods and Lac Seul and Comparable Percentiles for June 1-10

This higher than normal precipitation caused the levels of Lac Seul and Lake of the Woods to remain relatively stable over the month of July, rather than continuing or starting to decline. Some tributaries saw temporary increases in flows, especially those located where very high precipitation pockets occurred. The levels along the English River and the Winnipeg River in Manitoba did continue to decline. While levels on the Winnipeg River in Ontario remained stable. 

Both Rainy and Namakan Lakes fell below their respective All Gates Open levels in July and re-entered their rule curves in early August. This return to normal levels upstream of Lake of the Woods has allowed for significant outflow reductions from Rainy Lake. With these outflow reductions, and should precipitation conditions remain normal in August, the level of Lake of the Woods will start to decline at a much faster rate than in July.