The last six weeks have brought unprecedented rainfall broadly across the region. Watershed-wide precipitation statistics kept by the LWCB show the highest rainfall for the last 6 weeks (Aug26-Oct 6) on record in the local Lake of the Woods basin, the local Winnipeg Rivers basin in Ontario and in Manitoba, and the second highest in the Rainy-Namakan basin, 1 mm shy of the record.
Normal rainfall totals for this period are less than half these amounts. (See attached.)
Following more rainfall over the weekend and with more wet weather in the near-term forecast, the LWCB directed increases in outflow today from Lake of the Woods as follows:
Monday, October 7:
Increase from 1140 m³/s to 1200 m³/s
Expected river level rise from this flow adjustment:
Below Norman Dam: 23 cm (9 in)
Above Kimberley Rapids 19 cm (7.5 in)
Winnipeg River Marina 20 cm (8 in)
Near Locke Bay 19 cm (7.5 in)
Above Myrtle Rapids 19 cm (7.5 in)
Above the Dalles 19 cm (7.5 in)
Above Throat Rapids 19 cm (7.5 in)
Minaki 14 cm (5.5 in)
Thursday, October 10 (tentative):
Fully opening Norman Dam
Expected outflow: 1275-1300 m³/s
Expected river level rise from this flow adjustment:
Below Norman Dam: 20 cm (8 in)
Above Kimberley Rapids 17cm (7 in)
Winnipeg River Marina 19 cm (8 in)
Near Locke Bay 18 cm (7 in)
Above Myrtle Rapids 18 cm (7 in)
Above the Dalles 18 cm (7 in)
Above Throat Rapids 18 cm (7 in)
Minaki 13 cm (5 in)
As with recent flow increases, the further downstream from Norman Dam, the longer it will take for the change to develop. The level at Minaki will is expected to take several days to adjust to each flow increase.
Due to the exceptionally wet conditions, these outflow increases as necessary to allow for lake level decline ahead of freeze-up. Failure to lower the lake before freeze-up substantially increases the risk of high river flows during the winter and during the spring melt.
With little storage room in the lake, even a moderate spring melt response could result in river flows similar to now, but with the added issue of ice on the river. A very strong spring melt response would result in exceptionally high spring water levels and flows if starting with a high lake level.
Please share this information with others along with others along the Winnipeg River. People may be added to this distribution list by emailing secretariat@lwcb.ca with their name and location along the river.
