LWCB Monday, October 7th River Level Update; LOW Outflow Increase

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.