Runoff from the recent storm is not very large but significant with respect to Shellmouth Reservoir, which was 1.8 feet over the spillway when the rain began. The Assiniboine River is still rising at Sturgis and will keep rising at Kamsack for another 4 days or so. The Shell River is rising at Roblin and is expected to crest at Inglis near the end of May.

The Shellmouth Reservoir water level declined slightly to 1410.24 feet this morning due to north winds abating to calm conditions. The reservoir inflow this morning was 1900 cfs and the total outflow 1750 cfs. The conduit flow was increased to 400 cfs this morning while1350 cfs was going over the spillway. Conduit flows will be reduced to prevent total outflows from exceeding 1800 cfs as long as possible.

Minor flooding of the lowest lands in the Assiniboine Valley from Shellmouth Dam to Millwood is taking place at this time, mostly due to lack of good drainage due to the high river levels rather than due to overflows. Some overbank flow is expected to develop next week as total reservoir outflows reach 1900 cfs.

Portions of the Assiniboine River from St. Lazare to Brandon will experience rises of about one foot due to this week’s rain.

Areas from Dauphin to The Pas: 

A general rainfall of 50 mm with 70 mm in some localities has resulted in high flows on most streams in regions from Dauphin to the Red Deer River. Some streams flowing off the Duck and Porcupine mountains are running nearly full and in some cases higher than during the April crest. Some flash flooding occurred earlier this week but this has mostly subsided. Larger streams such as the Swan River, Woody River, Red Deer River are still rising and are expected to crest this weekend or early next week. Minor rises are likely on the Carrot River. Despite the high flows on these larger rivers, flooding is not expected. The level of Red Deer Lake is three-quarters of a foot lower than its crest in early May and is expected to crest about half a foot below the previous crest at the end of May based on average precipitation from now on.

The level of Lake Winnipegosis will rise further due to the heavy of the past week and is now expected to slightly exceed the peak level experienced during 2006. Flooding of low-lying lands near the lake is likely when strong on-shore winds develop.

Other Areas of Southern Manitoba: 

Some areas experienced minor overland flooding due to Monday night’s downpours but that ended within a day or two. Most streams in the areas south of a line through Dauphin and Hodgson have crested but some larger streams such as the Little Saskatchewan River, Birdtail Creek, Whitemud River, Icelandic River, Pembina River are still rising at some points. While flows are well above average, flooding is not expected on streams in this region. Only minor rises are expected on the Red River, lower Assiniboine River and Souris River.