Manitoba Water Stewardship’s first spring flood outlook for 2010 calls for significant flooding on the Red River in southern Manitoba, with average weather from now through spring, but anticipated levels would be 0.3 to 0.9 metres (one to three feet) lower than last year. The run-off on the Red River in Manitoba is expected to be above average from Emerson to Morris but average from Morris through Winnipeg and into Lake Winnipeg. Run-off on the U.S. portion is expected to be well above average.
The potential for spring flooding in Manitoba will largely depend on weather conditions. With unfavourable weather, conditions along the Red River could be about 0.3 m (one ft.) higher than in 2009, but still 0.3 to 0.6 m (one to two ft.) lower than in 1997. The timing and speed of the eventual breakup and the amounts of precipitation in the next eight to 10 weeks will have considerable effect on the flood potential.
Elsewhere, flooding in low-lying areas of the Interlake and along the Souris River watershed is also likely, with average weather patterns through spring.
Red River
The current conditions in the Red River watershed in Manitoba are:
• Soil moisture levels in Manitoba are above average, but not as high as last year.
• Snow cover is above average south of Morris and average from Morris to Lake Winnipeg.
• Ground frost depth is about 0.6 m (two ft.).
• Ice thickness ranges from 0.46 to 0.6 m (1.5 to two ft.) in most areas. Ice quality varies from strong in the Ste. Agathe area to fairly weak in Selkirk area.
• Winter river flows are above the usual amount.
Red River peak stage forecasts, based on normal ice conditions, are as follows:
• Favourable weather – several feet lower than 2006 (minor to moderate flooding).
• Average weather – 0.3 to 0.9 m (one to three ft.) lower than 2009 (extensive flooding).
• Unfavourable weather – approximately 0.3 m (one ft.) higher than 2009 but 0.3 to 0.6 m (one to two ft.) lower than 1997 in most locations (severe flooding).
• The probability of a 2009 flood or greater, ranges from 40 per cent at Emerson to about 25 per cent at St. Adolphe.
• Levels from Winnipeg to Breezy Point are expected to be significantly lower than 2009, unless serious ice jams develop.
The Red River watershed in the U.S. is as follows:
• Soil moisture is very high upstream of Halstad, N.D., similar to 2009.
• October was very wet in the Fargo, N.D., area.
• Snow cover in the U.S. portion is well above average, with heavier amounts upstream of Grand Forks, N.D.
• There is a high potential to have a run-off of 2009 levels proportions south of Halstad.
Interlake
The current conditions in the Interlake area are:
• Topsoil moisture is near normal but subsoil moisture is relatively high due to wet conditions during the past few years. Low areas and interior lake levels are still high.
• Snow cover is average.
Flooding potential is as follows:
• Favourable weather – flooding should be minor and localized.
• Average weather – low areas will likely sustain some flooding but less than last spring.
• Unfavourable weather – significant overland flooding and some overbank flows on streams such as Fisher River and Netley and Wavey creeks. Peguis and Fisher River First Nations would likely be affected.
Souris River Watershed
• Soil moisture is above average from Minot, N.D., to Melita and about average on other portions of the Souris River.
• Snow cover is above average in much of the watershed but is not as heavy in North Dakota as last winter.
• Significant amounts of the run-off will be stored on reservoirs in Saskatchewan and North Dakota.
Souris River peak stage forecasts are as follows:
• Favourable weather – minor flooding of farmland from the U.S. boundary to Hartney.
• Average weather – moderate flooding with stages 0.3 to 0.6 m (one to two ft.) lower than last spring.
• Unfavourable weather – extensive flooding with stages close to 1999.
Eastern Manitoba
• Soil moisture is above average in Whiteshell and Nopiming provincial parks and the Whitemouth River watershed but average in the Brokenhead River watershed.
• Snow cover is average to below average including in the Winnipeg River watershed.
Flooding potential is as follows:
• Favourable weather – flooding is unlikely.
• Average weather – lakes in the Whiteshell and Nopiming provincial park areas could rise somewhat above desirable levels.
• Unfavourable weather – flooding of low areas along the Whitemouth and Brokenhead rivers would likely occur and lakes would rise well above their target levels, with some shoreline flooding.
Assiniboine River Watershed
• Soil moisture is close to average in most areas.
• Snow cover is above average from St. Lazare to Brandon and average upstream of St. Lazare and Brandon to Winnipeg.
• The Shellmouth Reservoir will be used, as usual, to contain run-off with normal weather conditions. A normal winter drawdown is in progress.
River peak stage forecasts are as follows:
• Favourable weather – no flooding.
• Average weather – close to bank full.
• Unfavourable weather – significant flooding from Shellmouth to Grand Valley. Minor flooding possible in Baie St. Paul to Lido Plage and along Sturgeon Creek.
Pembina River Watershed
• Soil moisture is close to average, which is much lower than last February.
• Snow cover is significantly above average both in Manitoba and on the U.S. portion of the Pembina River.
Flooding potential is as follows:
• Favourable weather – minor localized flooding.
• Average weather – some over-bank flows from Rock Lake to Swan Lake.
• Unfavourable weather – flooding of agricultural land in most of the valley but not as much as 2009. There could be concerns for low-lying cottages on Rock Lake.
Westman Region
• Soil moisture is mostly average but above average in some areas.
• Snow cover ranges are average to below average.
Flooding potential is as follows:
• Favourable and average weather – flooding is unlikely.
• Unfavourable weather – minor, localized flooding could occur, especially if there is a rapid melt.
Northern Manitoba
Soil moisture is generally near normal and snow cover is below average.
Flooding potential is as follows:
• Flooding is unlikely with average weather conditions but localized flooding could occur with unfavourable weather.
Provincial Preparedness
• The Manitoba Emergency Measures Organization (EMO) has contacted communities to ensure they are prepared and many of these communities have exercised their emergency plans.
• Numerous local emergency operation centres made improvements based on lessons learned from last year’s flood and training of municipal employees has been provided.
More details on the 2010 flood outlook are at available online.
