FRANCAIS

February 26, 2004

Manitoba’s spring flood potential is relatively low in the Red River Valley but localized flooding of low-lying agricultural lands could occur in some watersheds. Aquifers will be slow to recover following the drought, according to Manitoba Water Stewardship.

In its first spring flood and water supply outlook for 2004, the Hydrologic Forecast Centre suggests that, despite above average snow in many areas, dry soil conditions and low ground areas are expected to absorb most of the run-off from melting snow.

With normal weather conditions from now on, the Red and Assiniboine rivers are expected to remain within their banks this spring. The Souris River will likely produce flooding of low-lying agricultural lands from the international boundary to Hartney.

Smaller streams in southern Manitoba are expected to remain within banks unless above average precipitation or a rapid melt develops.

However some watersheds, mainly from the Brandon area east to Winnipeg and to the northern Whiteshell, may experience localized flooding of low-lying areas on fields and along streams.

Most areas of western Manitoba have above average snow cover but should not experience flooding due to the very dry conditions experienced in the summer of 2003.

Flooding could occur on some smaller streams in the Riding, Duck and Porcupine mountain regions if a rapid melt develops.

Most lakes should rise to near normal levels but some large lakes will remain lower than desirable because of existing low levels resulting from drought conditions last year.

With average to above average snow cover across southern Manitoba spring run-off should be sufficient to replenish reservoirs, aquifers and on-farm water supplies. Aquifers will be slow to recover as dry soil soaks up meltwater but, with normal weather conditions from now on, conditions should be better than last summer.

Most of northern Manitoba is likely to experience a well below average spring run-off due to below average snow cover and dry conditions.

Water supplies for hydroelectric generation should be improved over last year but will likely remain less than optimum.

Red River - Flooding is not expected with normal weather conditions during March and April.

• There is well below average snow cover over most of the watershed.
• Soil moisture is below average.
• There is a one-in-ten chance that adverse weather could produce levels nearly as high as those of 2001, when minor over-bank flows occurred.

Assiniboine River - Flooding is not expected with normal weather conditions from now on.

• Snow cover is above average but soil moisture is well below average.
• There is a one-in-ten chance that adverse weather could produce flows to the tops of riverbanks on the Assiniboine from Portage la Prairie to Winnipeg with river ice in place with little or no ice jamming.
• The Portage Diversion will operate to minimize the risk of ice jamming.
• Ice jam related flooding from Portage to Headingley is possible.
• Operation of the Shellmouth Reservoir is expected to prevent flooding from Shellmouth to Brandon.

Souris River - Normal weather conditions will produce significant flooding of agricultural lands from the international boundary to Hartney with peak stages similar to those of 2001.

• Snow cover is well above average but soil moisture is well below average over most of the watershed including Saskatchewan and North Dakota.

Winnipeg River – The chance of spring flooding along the Manitoba portion of the river is low and there is still concern about possible low flows and levels this spring and summer.

• Soil moisture is above average in the English River system but below normal in the Lake of the Woods system.
• Snow cover is near normal in the English River portion but below normal in the Rainy River system.
• Conditions are considerably better now than they were last year at this time.

Saskatchewan River - Spring flooding is unlikely at The Pas unless ice jams develop.

• Both soil moisture and snow cover are generally below average in the plains portion of the watershed.
• Mountain snowpack is close to normal.
• Saskatchewan Watershed Authority predicts run-off volumes from March to July will be about 80 per cent of normal.
• Flows at The Pas this spring and summer are likely to be below average and similar to those of 2003.

No substantial flooding is expected on smaller watersheds with normal weather during March and April. However a number of smaller watersheds may experience minor localized flooding of low-lying areas.

Water Stewardship will continue to monitor watershed conditions and will issue an update if conditions change substantially.

- 30 -

NOTE: The full spring flood and water supply outlook report is available on the Manitoba Water Stewardship website at:

• soil moisture survey done in late October 2003 using an airborne gamma method
• modelled soil moisture for Oct. 31, 2003, provided by Environment Canada
• snow survey conducted in mid-February 2004 in western Manitoba from Riding Mountain north to Flin Flon, in the Interlake, and in southeastern and south-central Manitoba
• satellite microwave snow cover maps provided by Environment Canada
• daily and monthly precipitation and temperature data from Environment Canada
• recent river levels, flows and ice thickness from Water Survey of Canada and Manitoba Conservation
• data and flood outlooks for upstream portions of the Red, Souris, Qu’Appelle and Saskatchewan rivers, obtained from the U.S. National Weather Service and the Saskatchewan Water Corporation
• information on controlled lakes in northern Manitoba, from Manitoba Hydro

It was an unusually hot, dry summer across most of Manitoba. Autumn precipitation was substantial in the Whiteshell, portions of south-central Manitoba and in the The Pas area.

Long range weather predictions from Environment Canada will not be updated until March 1, 2004. The U.S. Climate Prediction Center, in its Feb. 19 update, calls for a cool spring in areas adjacent to southern Manitoba. It is not known whether precipitation will be above or below average.

An airborne moisture survey of the top 20 cm (eight inches) of soil conducted in late October, 2003 showed topsoil moisture well below average as of Oct. 25. There was some snow in late October and November which melted, replenishing topsoil moisture to some extent.

Soil moisture levels of Oct. 31, 2003, from Environment Canada were quite dry in western Manitoba except for regions around The Pas where it was wet. It was near normal in most other areas except in extreme southeastern Manitoba where it was above average.

Winter precipitation up to Feb. 19 has been average to above average across most of southern Manitoba but has been generally below average in northern Manitoba.

Research from the Climate Research Branch of Environment Canada shows that snow cover is quite high in southwestern Manitoba and southeastern Saskatchewan and relatively low in most of the Red River watershed.

An airborne snow survey by Manitoba Water Stewardship under contract with the U.S. National Weather Service shows that the water content of snow is between 2.5 and 3.5 inches (64 mm to 89 mm) in most areas of southern Manitoba. A band from Spruce Woods to just north of Winnipeg has close to four inches (102 mm) of water. These amounts are generally above the average of the airborne data for the past 10 years.

A conventional snow survey conducted by Manitoba Water Stewardship Feb. 9-12 shows that snow cover is above average in the vicinity of the Riding, Duck and Porcupine mountains as well as in the Interlake, south-central Manitoba and parts of southeastern Manitoba. Snow cover is below average in the Morris, Morden and Carman areas and close to average in regions near The Pas.

River flows as of late February were generally much below average due to the drought of 2002-03. Many rivers were at 10 year lows. Flows in eastern Manitoba were closer to the median due to a wet autumn in that area.

River and lake ice thickness appear to be average to below average, ranging from 1.5 to 2.5 feet (0.45 to 0.76 metres) in much of southern Manitoba. Ice thickness on rivers can vary greatly depending on velocity, depth, snow cover and weather conditions.

Most reservoirs operated by Manitoba Water Stewardship were more than 70 per cent full in late February and are expected to fill this spring.

A few reservoirs, such as Goudney, Irwin, Turtlehead Creek (Deloraine) and Vermilion are quite low. However they should be close to full following spring run-off unless dry conditions and a slow melt develop.

The water level in Shellmouth Reservoir is above average for this time of year due to careful conservation throughout 2003. Outflows will be maintained at 150 cubic feet per second unless the predicted spring inflow increases significantly. Water supplies in the reservoir should be in good condition to meet downstream needs in 2004.

Levels of most major aquifers dropped in 2003 and are well below average levels but should meet needs for the rest of this winter. A good spring recharge is needed to prevent further declines in aquifer levels in 2004. Significant amounts of snow melt may recharge soil moisture with recovery of aquifers typically slow during the first year following a drought.

If there is little additional precipitation in March and April, aquifers may rise very little. This could result in problems with aquifers later in 2004, especially if followed by another hot, dry summer resulting in high withdrawals.

With normal weather conditions from now on, aquifer levels in 2004 should be no lower than in 2003 avoiding major problems with the odd exception such as the Ogilvie aquifer northwest of Gladstone.

On-farm water supplies such as shallow wells and dugouts are generally in poor condition in almost all of southern Manitoba except in areas east of the Red River. There should be a good recharge this spring unless the weather is dry for the next few months. There should be sufficient water sources in most areas this spring for refilling of dugouts by pumping if necessary. Manitoba’s Water Services Board will assist farmers by providing pumps.