While spring run-off and the threat of flooding have subsided in many areas of Manitoba, higher-than-normal precipitation in some areas of the province has resulted in persistent high flows on streams and high lake levels. The upper Assiniboine River basin, the Lake Winnipegosis basin, the Dauphin Lake basin, and eastern Manitoba, including the Winnipeg River and many of the lakes in the Whiteshell Provincial Park, have all been experiencing precipitation up to 200 per cent higher than normal. Over the next two days, widespread precipitation is expected across much of western Manitoba and for portions of eastern Manitoba.
Flood Warning Issued for Dauphin Lake
Manitoba Infrastructure and Transportation’s Hydrologic Forecast Centre has issued a flood warning for Dauphin Lake. The lake is currently at 857.9 feet above sea level (fasl), approaching the flood stage of 858 feet. Recent rainfall in the area has caused high inflows to the lake and the lake level is expected to continue to rise over the next week.
The Dauphin Lake basin has received significant precipitation in April and May. The area is expected to receive another 10 to 15 millimetres of precipitation in the next few days.
The forecast wind-eliminated level at Dauphin Lake is expected to reach between 858 and 858.2 fasl between May 29 and June 5.
Following the 2011 flood, the majority of properties along the lake have upgraded their flood protection level to 863 fasl.
If strong winds occur while the lake level is high, it could result in damaging wave action along the shoreline, depending on wind direction.
The record-high lake level was observed in mid-June 2011 at 860.76 fasl. If the lake reaches the upper range of the forecast, it will be 2.5 ft. below the 2011 peak water level.
Outflow from Dauphin Lake on the Mossy River is 2,070 cubic feet per second (cfs). The Mossy River Control Structure has been wide open in recent years due to a persistently high water level.
Lake Manitoba
Lake Manitoba is approximately 1.8 ft. below unregulated levels, meaning the lake is 1.8 ft. lower than what it would have been if there was no provincial water control infrastructure affecting inflows and outflows to the lake. The lake is lower than it would have been because the additional outflow provided by the Fairford River Water Control Structure is realized year round, not only during the relatively short period the Portage Diversion is in operation.
Lake Manitoba is currently at approximately 813.1 fasl, 1.1 ft. above the desired level for this time of year. Flood stage on Lake Manitoba is 814 ft.
Lake Manitoba is forecast to peak at 813.5 to 813.8 ft. in late June to early July.
At this time, the Waterhen River is flowing approximately 9,700 cfs from Lake Winnipegosis into Lake Manitoba. Flows on the Waterhen River are controlled by the levels on Lake Winnipegosis; Lake Winnipegosis is very high and is projected to continue to rise until mid-June.
Outflow from Lake Manitoba today is approximately 11,760 cfs. The estimated natural outflow from Lake Manitoba at the current lake level, if the Fairford River Water Control Structure and associated channel improvements hadn’t been constructed, would have been approximately 3,300 cfs.
The Fairford River Water Control Structure at the outlet of Lake Manitoba is being operated for maximum possible discharge and has been since 2005. The structure has remained fully open nearly continuously, allowing for maximum possible outflow, due to ongoing high water levels on Lake Manitoba.
Lake St. Martin
Lake St. Martin is currently at 802.3 ft.
If Lake St. Martin rises higher than 803 fasl, the province may reactivate the emergency outlet channel, which will increase the outflow from Lake St. Martin to Lake Winnipeg.
Lake St. Martin is expected to peak between 802.9 and 803 ft. in mid-July.
Any emergency operation would need to be authorized by the federal and provincial regulatory agencies.
Heavy equipment that can be used to activate the channel is stationed at the outlet.
Assiniboine River
The water level on Shellmouth Reservoir is at 1,406.5 ft.; the summer target level is 1,402.5 ft. and the spillway is at 1,408.5 ft. Earlier this month, the water level exceeded the spillway elevation and the reservoir has been drawn down to create storage space in case of future summer storm events. Inflows to the reservoir are approximately 2,500 cfs today; outflows from the reservoir are at 1,500 cfs this morning and will be reduced to 1,000 cfs later today.
As of this morning, flow on the Portage Diversion is 7,440 cfs and flow on the Assiniboine River downstream of the diversion is 10,450 cfs.
Earlier this week, flows on the lower Assiniboine River were increased to 12,000 cfs in order to divert less water to Lake Manitoba. However, some flooding of downstream land was experienced due to impaired drainage into the river combined with recent precipitation and seepage under the lower Assiniboine dikes.
The provincial government is working toward a long-term plan to improve the reliable capacity of the lower Assiniboine River.
Winnipeg River System
The Winnipeg River, which originates in northwest Ontario fed by flows from Lake of the Woods and the English River system, continues to see very high flows.
A number of lakes in the Whiteshell Provincial Park, including Nutimik, Dorothy and Eleanor lakes, are a part of the Winnipeg River system.
Water levels on Nutimik Lake are high enough that boathouses around the lake are being affected. Levels were last this high in 2008 and 2009 but, depending on weather, there is concern the lake could go even higher this year.
Today’s water level on Nutimik Lake is 906.5 ft. and the peak observed water level this year was 906.7 ft. on May 26.
Lakes in Whiteshell Provincial Park
A flood watch has been issued for the lakes in the Whiteshell Provincial Park.
High water levels have been observed on the Whiteshell Provincial Park lakes following snowmelt and significant precipitation in late April and early May. Some of the lakes have reported record-high water levels. Levels have been dropping on most lakes since then. However, forecast precipitation of 20 to 30 mm in the region over the next few days could cause the levels to rise significantly.
Current levels on some of the lakes is given below:
- Brereton Lake: 1,037.17 ft. (peak observed level 1,038.15 ft. on May 2);
- West Hawk Lake: 1,093.35 ft. (peak observed level 1,093.5 ft. on May 17); and
- Caddy Lake: 1,047.8 ft. (peak observed level 1,048.95 ft. on May 20).
The Pas/Saskatchewan River
Flow on the Saskatchewan River at The Pas is relatively stable at 58,840 cfs. The water level is 853.2 ft., approximately 4.1 ft. below the peak water level which occurred on May 5. The water level and flow continue to be monitored closely.
Whitewater Lake
Whitewater Lake remains at record high levels. The current lake level is 1.632.56 ft. and is forecast to peak between 1,633 to 1,633.3 ft. later this summer.
