The past week saw some much needed precipitation in a large portion of the Winnipeg River basin. According to the U.S. Drought Monitor, drought categories for some Minnesota portions of the basin improved from Exceptional to Extreme Drought or from Extreme to Severe Drought.
However, due to the widespread drought conditions, little of this rainfall has reached streams and larger tributaries in the basin. Substantial rainfall is still needed to resolve the underlying drought conditions in the landscape and return flows to normal.
Water levels in key reservoirs upstream of Lake of the Woods, Rainy Lake and Namakan Lake, rose modestly but remain below regulatory targets set by the International Joint Commission. As a result, there has been no increase in the very low seasonal outflows from the dams at these lakes.
Flows in the Rainy River and its main tributaries, the Big Fork River and Little Fork River, saw very small responses to the rainfall. Inflow to Lake of the Woods has not increased significantly as a result.
The current level of Lake of the Woods is 322.50 m (1058.1 ft), a 5th percentile level for this time of year. The lake level declined by 1 cm (1/2 in) over the past week and is expected to decline by 1-3 cm over the next week with forecasted dry weather. Lake of the Woods authorized outflow is 100 m³/s, with no outflow changes currently scheduled.
In the English River basin, the rainfall led to a greater rise in tributary flows in some areas, for example near Sioux Lookout and the Chukuni River where flows are now in the normal range for late September. Other tributaries remain well below normal, as does the level of Lac Seul and the mainstem of the English River as measured at Grassy Narrows.
The current level of Lac Seul is 355.62 m (1166.7 ft), less than 5th percentile for this time of year. The lake level rose by 6 cm (2 in) over the past week and is expected to rise by 1-3 cm (1 in) over the next week. Lac Seul authorized outflow is 75 m³/s with no changes currently scheduled. A planned regional power outage scheduled by Hydro One will result in fluctuations in outflow from Lac Seul on September 26 and 27, varying between 39 and 107 m³/s before returning to the authorized 75 m³/s.