Condition Reports

Report on Spring Runoff and Flood Conditions for Manitoba

April 16, 2008

Overview:

Spring runoff in most areas of southern Manitoba has been well below average as was predicted in the flood outlooks issued during February and March. Dry spring weather has contributed to the low runoff. This is the lowest spring runoff since 2003. There has been little or no flooding in most areas and no significant ice jams have occurred.

As of mid April, 2008, all streams in southern Manitoba had crested except for the Assiniboine River. Brief flooding occurred in the Duck and Porcupine Mountain areas due to a rapid melt April 12-14. Runoff is just beginning in areas from The Pas northward.

There is some concern that river flows and levels in southern Manitoba may decline to undesirably low conditions this summer if the weather remains dry.

Red River:

The Red River crested at 11.5 feet in downtown Winnipeg on April 15. The crest is presently in the Selkirk area and will reach Breezy Point by tomorrow. The Red River has remained well within it banks this spring and operation of the Red River Floodway has not been required.

Ice jams, which produced record flooding at Selkirk in 2007, have not developed so far this year due to low river flows and due to extensive ice breaking activities from Selkirk to Lake Winnipeg. Ice was moving in the Selkirk area today with no significant jamming was evident.

This year’s crest in Winnipeg is the lowest since 2003 when the river crested at 7.1 feet. Other low crests occurred in 2000 and 2002 when the river rose to only 6.9 feet. Since 1995 the spring crest at Winnipeg has been above 17 feet ten times. This is the fourth low flow year during this 14 year period. 

 The Forks walkways, which are at an elevation of 9 feet, are presently inundated but are expected to emerge as early as this weekend. This is in stark contrast to 2007 when the walkways were under from March 29 to April 23 and from May 29 to July 11.

Assiniboine River:

The Assiniboine River crest is presently between Miniota and Virden and is expected to reach Portage la Prairie by April 23. Peaks stages will be lower than in recent years and no flooding is anticipated. Operation of the Portage Diversion is unlikely but it will be operated temporarily if high ice flows develop in the area.

Shellmouth Reservoir levels are presently on the rise due to recent warm weather. It is anticipated that the reservoir water level will rise somewhat above the summer target level by the end of April. While it may be necessary to increase outflows somewhat, downstream flooding is unlikely unless adverse weather develops during the next 3-4 weeks.

Souris River:

Flows in the Souris River have risen very little this spring and remain very low. A release of 20 cubic feet per second from reservoirs in the United States beginning May 1, as per International agreement, will provide adequate river flow this summer.

Pembina River, Smaller Streams:

The Pembina River and smaller streams south of  PTH #1 experienced well below average flows this spring and have been declining for a week or so. There has been no flooding.  A moderate  runoff has occurred on the Whitemouth River, Whitemud River, and on streams in the Interlake but even here flows are generally below average.

Runoff is unusually low in the Whiteshell area, where logs are being added to dams in an attempt to raise lakes to their desirable summer level.

Riding, Duck and Porcupine Mountain areas:

Flash flooding occurred last weekend when temperatures soared to above 20 degrees C. Some roads were overtopped and a few homes were briefly threatened but damage was minimal. The failsafe at the Gilbert Plains Dam was washed out, flooding a nearby golf course. River levels have subsided are all back within their banks. Runoff from the high ground is underway but will not create any difficulties unless heavy rain develops during the next weeks or so.

The Pas area:

Runoff is underway and most streams are expected to crest next week. Flooding is not anticipated.

Reservoirs:

Runoff has been sufficient to fill most water supply reservoirs but some lakes have not recharged fully. Lakes which may be below their desirable levels include Pelican Lake, Oak Lake, Whitewater Lake, Dauphin Lake and most lakes in Whiteshell Provincial Park.

Aquifers, On-Farm Water Supplies:

Data on aquifer recharge is not yet available, but it is likely that most aquifers south of PTH #1 had a below average recharge. Some shallow aquifers may have unusually low levels later this year. On-farm water supplies are low in southwestern Manitoba, where water is being pumped to fill dugouts as best possible. Water hauling may be necessary this summer of dry weather continues.

Weather:

Precipitation from during the rest of the spring and the summer of 2008 will be highly significant to the conditions of rivers, lakes and reservoirs in Manitoba. Continued dry weather could result in some difficulties this summer.

Hydrologic Forecast Centre
Regulatory and Operational Services,
Manitoba Water Stewardship