Manitoba Water Stewardship

A stationary upper low pressure system over the western Dakotas continues to produce unsettled weather over southern Manitoba with heavy localized precipitation in thundershowers. Occasional showers or thundershowers are expected for the next three days, mainly over the Red River watershed and eastern Manitoba, according to Environment Canada. However the weather system appears to be weakening and may not produce much more heavy rain.

While most areas of southern Manitoba and eastern Saskatchewan received little rain during the past 24 hours, the northern Whiteshell and southern Nopiming Park received heavy thunderstorm rainfall last night with 83 mm reported at Flanders Lake.

Additional rainfall is expected during the next few days, but it appears that heavy rainfall will be limited to southeastern Manitoba. Rainfall in western Manitoba and eastern Saskatchewan will likely be in the 5-15 mm range.

Winds over Shellmouth Reservoir are expected to be moderate northerly today and tomorrow.

A FLOOD WARNING CONTINUES FOR THE ASSINIBOINE RIVER FROM SHELLMOUTH TO MILLWOOD.

The Shellmouth Reservoir water level rose 0.07 feet in the past 24 hours and stood at 1410.22 feet this morning under relatively light winds.

The reservoir inflow had risen to 2070 cfs this morning and is expected to crest at 2250 cfs later this week based on little additional rainfall. The predicted inflow has been raised somewhat due to a continued rise of the Whitesand River which drains into the Assiniboine River just upstream of Kamsack. The river is presently at its crest at Sturgis, SK. The Shell River is expected to crest near Inglis during the next few days.

The total reservoir outflow rose briefly to 1850 cfs early this morning but was reduced to 1650 cfs at 10:30 a.m. when the conduit flow was reduced from 500 to 300 cfs. The reduction was made in part due to expected northerly winds today which will increase the spillway flow. Conduit flows will continue to be adjusted as required to prevent total outflows from exceeding 1750 cfs as long as possible.

The amount of rainfall during the next few days will determine whether it will be possible to keep peak reservoir outflows below 1750 cfs. If rainfall is 10 mm or less it should be possible.

The level of Red Deer Lake rose 0.2 feet since yesterday morning to a level just 0.3 feet below the crest of early May. A part of this rise of was due to a strong northeast wind. The Porcupine Mountain area received additional rain in thundershowers last night, raising inflows on local streams flowing into the Lake. The Red Deer River crested at Erwood, SK a few days ago. Little further rise is expected on the Lake unless additional heavy rain develops in the next few days.

Levels if the Carrot River and the Saskatchewan River are falling slowly but remain very high. Some smaller streams in the vicinity of The Pas, such as the Birch River, are above flood stage causing flooding of at least one farm. Ducks Unlimited has opened Bracken Dam to allow more water to flow into the Saskatchewan River, which should allow levels on the Birch River to decline.

The crest on the red River is in the Emerson area and should reach Winnipeg later this week. The river level in the City of Winnipeg rose to 9.5 feet this morning, which is one foot higher than the lowest walkways at the Forks. A further rise of less than one foot is expected based on little additional rain.

Heavy thunderstorm rainfall of up to 85 mm occurred in the extreme northern part of the Whiteshell and in southern portions of Nopiming Provincial Park last night causing some road washouts and localized flooding. The community of Point du Bois was temporarily isolated.

Overland flooding could develop in other portions of southeastern Manitoba and the Red River Valley if more than 40 mm of rain develops during the next few days, especially of the rain comes in the form of thundershowers. Soil moisture levels are unusually high due to recent rains. However the latest weather forecast suggests that rainfall amounts during the next three days are likely to be less than 25 mm.