Manitoba Water Stewardship officials have issued a high-water advisory for the southern Interlake and areas northeast of Winnipeg to Nopiming Provincial Park. Recent weather produced
45 to 55 millimetres (1.8 to 2.2 inches) of rain in the areas Saturday evening through Sunday, resulting in widespread overland flooding with overloaded drains and ditches. Water levels have begun to decline but it will take weeks of favourable weather for conditions to return to near normal. Additional rain in the next few weeks could worsen and extend the flooding.
Many areas of Manitoba also received heavy rains but amounts were generally under 10 mm (0.4 in.) in western Manitoba and less than 20 mm (0.8 in.) in the Red River valley and the Whiteshell.
The flood watch issued for southern Manitoba Friday has ended, however, a flood warning continues for the Assiniboine River valley from Shellmouth to Brandon. The weather forecast calls for showers in western portions of southern Manitoba Thursday and in eastern portions late Thursday to Friday. Precipitation is also likely next weekend.
Duck Mountain and Eastern Riding Mountain Areas
– Overland flooding is subsiding in most areas but continues in some areas near the Duck Mountains which received up to 20 mm (0.8 in.) rain yesterday. Additional rain of 25 mm (one in.) or more later this week would cause renewed overland flooding.
– The Shellmouth Reservoir rose three centimetres (1.2 in.) since yesterday and stood at 430.3 metre (1,411.8 feet) this morning. The conduit flow was reduced from 450 to 250 cubic feet per second (cfs) at 8 a.m., to 150 cfs at 3:50 p.m. yesterday and to 100 cfs at 1:20 p.m. today. The spillway flow this morning was 3,600 cfs, while the total outflow was 3,700 cfs following this afternoon’s change. The computed inflow this morning was 4,400 cfs. The reservoir is expected to crest at 430.3 m (1,411.85 ft.) today. This is the first time the spillway has been overtopped during the summer in 40 years of operation. The spillway elevation is 429.3 m (1,408.5 ft.).
– Tributaries of the Assiniboine River from Shellmouth to Brandon have crested except for the Qu’Appelle River which is expected to crest today. Predicted crests have been reduced slightly from Miniota to Virden but flooding of lower portions of the valley from St. Lazare to Brandon is still expected from now to early July. Flooding of valley lands from Shellmouth to Millwood will continue for the next few weeks. Operation of Shellmouth Dam has lowered crests along the Assiniboine River by close to 0.9 m (three ft.), greatly reducing the extent of flooding in the valley. Crests are expected at Miniota on June 29 to 30, Virden on June 30 to July 1 and Brandon on July 1 to 2.
– The Portage Diversion continues to be operated to reduce the risk of sewer backup in Winnipeg, should heavy downpours develop over the city. The diversion flow this morning was 5,505 cfs while the flow at Southport (downstream of the control structure) was 3,160 cfs. Diversion flows will increase until the end of this week as higher flows arrive from the Souris River and the upper Assiniboine River. Assiniboine River levels from Spruce Woods to the Long Plain First Nation are expected to gradually rise about 0.15 m (0.5 ft.) by next weekend. Levels have gone up more than 0.15 m (0.5 ft.) in recent days.
– Operation of the Red River Floodway control structure continues to be halted due to high flows on the Red River. Flows continue to rise slowly due to additional rain and will remain relatively high for the next seven to 10 days even without additional rain as a small crest moves up from the U.S. The flow at the floodway inlet this morning was 23,830 cfs.
– The river level in downtown Winnipeg stood at 3.55 m (11.66 ft.) at 9 a.m. this morning, a rise of 0.18 m (0.6 ft.) from Sunday. The level is expected to crest near 3.6 m (11.85 ft.) during the next few days. The natural level without operation of major flood control works was 4.29 m (14.06 ft.) this morning. Lowering of the floodway gates will resume once the river level in Winnipeg declines to 2.7 m (nine ft.).
Souris and Pembina Rivers
– Levels of the Souris River continue to rise slowly with a further rise of 9.1 cm (0.3 ft.) at Melita since yesterday. Additional rises will range from less than 0.15 m (0.5 ft.) at Coulter to about 0.46 m (1.5 ft.) from Melita to Wawanesa during the next five to six days. Flooding of agricultural lands in the Coulter area will increase substantially but flooding is not expected from Melita to Wawanesa.
– Pelican Lake levels remain above the summer target and operation of the outlet control works continues. The level of Rock Lake has risen 0.9 m (three ft.) since mid-June but the lake was cresting at 406.44 m (1,333.45 ft.) this morning. The record high peak level in 2009 was 408.25 m (1,339.4 ft.) about 0.9 m (three ft.) above the summer target level. Some flooding of low-lying properties has been reported. Minor flooding of low-lying agricultural lands is expected in the portion of the valley from Rock Lake to Swan Lake.
– Manitoba Water Stewardship and Manitoba Infrastructure and Transportation continue to operate control structures to reduce water levels as best possible. Many smaller lakes in southern Manitoba are at unusually high levels and larger lakes are on the rise. Lake Manitoba has risen to 247.57 m (812.25 ft.) which is a 7.62 cm (0.25 ft.) below the top of the operating range. Lake Winnipeg has risen to near the top of its range of regulation 217.9 m (715 ft.) and Manitoba Hydro has increased outflows from the lake to prevent further rises.