The Provincial June forecast for peak level of Lake Manitoba was 812.9 – 813.0 feet between June 24 and June 28:
We have now exceeded that forecast.
This morning, after the heavy rain yesterday and rain earlier in the week, the lake has risen to 813.04 feet and it will go higher as the rainwater drains off the landscape into the lake. The current level of the lake is well above the top end of its operating range (810.50 to 812.50 ft) and reaching flood level is no longer a remote possibility. In the short term, the lake will continue to rise until we get a stretch of hot dry weather. The good news is that flows on the Assiniboine are now falling, and the Portage Diversion is nearly closed, with a (negligible) flow this morning of just 174 cfs. But as Lake Winnipegosis (831.73 ft) rises, flow on the Waterhen River (the main river inflow to Lake Manitoba) is rising, reaching 4,979 cfs this week. As Lake Manitoba rises, outflow at Fairford rises, reaching 7,628 cfs this week. Flow on the Whitemud River is now falling, currently 1,971 cfs. Lake St. Martin rose this week to 800.50 ft: that is now a half foot ABOVE the top end of ITS desired operating range of 800.00 ft. Flow on the Dauphin River is up to 6,286 cfs, rising with the higher level of Lake St. Martin. Flow on the Assiniboine has crested and is falling, to 9,853 cfs at Holland and 10,241 cfs at Headingly. The level of the Shellmouth Reservoir fell this week to 1406.27 ft.
Right now long-range forecasts are a fool’s errand, as our erratic weather makes any forecast highly uncertain. But we only have 10-12 weeks of hot weather in front of us. If the remainder of the summer remains wet, we could be looking at very high lake levels on Lake Manitoba going into the fall. The worst flood in the last two centuries (higher than 2011) occurred not in the spring, but in the fall (of 1872). A wet fall could easily mean another flood on both Lake Manitoba (>814.00 ft) and Lake St. Martin (>801.00 ft).
River update
Time: June 25, 2022
Portage Diversion: 174 cfs
Assiniboine at Holland: 9,853 cfs
Assiniboine at Headingly: 10,241 cfs
Waterhen: 4,979 cfs
Whitemud: 1,971 cfs
Fairford: 7,628 cfs
Dauphin: 6,286 cfs
Lake update
Time: June 25, 2022
Steep Rock: 812.92 ft
Westbourne: 813.15 ft
Mean level Lake Manitoba: 813.04 ft
Lake Manitoba desired operating range: 810.5 to 812.5 ft
Lake St. Martin: 800.50 ft
Lake St. Martin desired operating range: 797.0 to 800.0 ft
Lake Winnipegosis: 831.51 ft
Shellmouth Reservoir: 1,406.27 ft
Extracted from the Environment and Climate Change Canada Real-time Hydrometric Data web site (https://wateroffice.ec.gc.ca/mainmenu/real_time_data_index_e.html) on June 25, 2022.
Association of Lake Manitoba Stakeholders 