Residents in the Winnipeg River Drainage Basin area, which includes Rainy Lake, Rainy River, and Lake of the Woods, could be faced with water levels at or exceeding those of 2014 depending on how much rain we see in the next few weeks, according to the Lake of the Woods Control Board (LWCB).
According to their website, the LWCB is a Canadian board that regulates the water levels of Lake of the Woods and Lac Seul, as well as the flows into the Winnipeg and English Rivers for the long-term benefit of the public and different businesses or organizations.
At a public information webinar presented by the LWCB secretariat staff on Tuesday, May 10, 2022, representatives discussed the high water levels that are being seen throughout the basin and numerous sub-basins due to a myriad factors, including snowfall, a late thaw and record high precipitation levels. According to the LWCB, it remains dependent on what additional precipitation we see in the region over the coming weeks as to whether we will see water levels below, at or even above the water levels recorded in 2014.
“To pull it all together, nearly all areas we’ve looked at, because of these exceptional flows are at risk of 2014 or higher levels, given that we’re just really starting the wettest period of the year,” the LWCB said.
“It’s not a guarantee we’re going to see wet weather, but it certainly isn’t unlikely. If [the amount of precipitation] is very high, water levels could get higher than 2014. We need an extended dry period and getting into warmer weather with plant growth, etcetera, to start to see a return to normal levels in most areas, and that is going to take a while.”
Even with the severe drought conditions experienced in the region in 2021, the conditions for a spring flood can be relatively removed from the weather of the previous year. The ingredients for flooding conditions in the spring are high base flows across the watershed, high water content in the snowpack left over from the winter, how frozen the ground is, and most importantly, the timing and amount of spring rainfall received in the basin.
When discussing base flows, the LWCB notes that high base flows indicate the ground has very low capacity to take on extra water. Meanwhile the water content of snow can vary depending on different weather conditions, so a large volume of snow at the end of winter doesn’t necessarily mean it will melt into a large volume of water. However, the LWCB noted that if the water content of the snowpack is high, and if the ground is either too saturated to take on more water, or stays frozen, then that snow melt will have nowhere else to go than into the basin system, which adds to the high water levels and increases the flood risk.
Most significant of the factors listed by the LWCB is the timing and amount of spring rainfall.
“If there’s a gradual melt and normal precipitation here and there, the whole watershed’s worth of snowpack can run off in a moderate way and can be handled by the various dams in the system without getting to a high flow condition,” the LWCB stated.
“However, if you get into a rain on snow condition, things can quickly deteriorate.”
All of these things added together can quickly and severely change the water levels and increase the flood risk to those living along the lake and river system.
The LWCB noted that for Rainy-Namakan Basin, 2021 saw drought conditions begin to ease in November as the base flow began to increase, coming closer to normal levels for that time of year. Those levels remain closer to average throughout the winter, and then increase dramatically in early April.
“It’s that consistency again,” the LWCB said.
“Five or six straight quarter-month periods with many multiples of the average precipitation we usually see in April for both the Rainy-Namakan and Lake of the Woods Basin.”
The LWCB said the Rainy-Namakan Basin saw 177mm of accumulated precipitation from December 1, 2021 to the end of March 2022, and as of the date of the seminar, that number had reached 332mm, almost double the rainfall in one month compared to all four of the preceding months combined. This extreme precipitation is the biggest driver of the high water levels in the region, according to the LWCB.
In a chart comparing the precipitation received in April 2022 to the current or previous year of record, almost every sub-basin save for the Lac La Croix has broken their previous record, with this April’s 123mm in the Rainy-Namakan basin tying the previous record set in 2001. Lake of the Woods has seen 134mm of rain in April 2022, beating out the record of 108mm set in 1986.
That increased precipitation coincided with a drop in temperatures to below-average levels for the latter half of April, which in turn prevented a moderate thaw over a longer period of time, which could have helped to reduce flow and lake levels.
While Namakan Lake and Rainy Lake both have dams that help to regulate water levels within, the LWCB stressed that those dams are monitored and controlled by the International Joint Commission (IJC), a separate board from the LWCB, and so the LWCB has no jurisdiction or control over those dams.
As of the date of the seminar, the inflow levels for water going into Rainy Lake are at 1,576m3/s, while the outflow levels are struggling to keep up at 960m3/s even with the Rainy River dam fully open. This is contributing to the continuing rapid rise of water levels in Rainy Lake. The LWCB noted the 2014 peak water levels are two feet higher than current water levels.
In the weeks to come the LWCB warns that Rainy and Namakan lake dams will remain fully open until the water recedes to regular levels, though that will take some time.
For more on the Lake of the Woods Control Board, as well as to see historical data and charts outlining lake and flow levels, visit their website at lwbc.ca.