Levels and Flows for Rivers, Lakes, Reservoirs and Aquifers

Water Supply Conditions for Manitoba

July 14, 2006

Precipitation from May to mid July, 2006 has been much below average in many areas of Manitoba. While a relatively short period of dry weather such as this is of prime concern to agriculture, it has raised some questions about the adequacy of water supplies. The following information is therefore provided.

• Most reservoirs in southern Manitoba are full close to full. This is due to the good recharge experienced this spring and the relatively high levels carried over from the wet conditions in 2005. Reservoir water shortages are unlikely this summer even if the weather remains dry. However reservoir levels could decline a fair amount due to evaporation and heavy uses. Releases are being made to meet downstream requirement and this will continue.
• Most lakes are at near normal or above normal levels for this time of year. The exception is the Whiteshell area, including Lake Of The Woods and Moose Lake, which are at below average levels, affecting recreation to some extent. Continued dry weather this summer would cause lakes to decline, but would not pose a serious problem this year.
• The Assiniboine River has well above average flows and will continue to supply plenty of water for irrigation and other throughout 2006.
• Flows in the Red River and the Souris River have declined to below average but these rivers are unlikely to fall to seriously low levels this summer. They may become seriously low in the autumn if dry weather continues.
• Levels of the Winnipeg River are well below average and could impact on hydroelectric production and recreation later this summer if dry weather continues.
• Flows and levels of many smaller streams in the Red River Valley and eastern Manitoba, such as the Roseau River, Seine River, Whitemouth River and many others are unusually low. If dry weather continues through August many of these streams could dry up, resulting in difficulties for people relying on river water. Some problems with water intakes have already been reported. While it is not very unusual for smaller streams to decline to a trickle during the late summer the decline is much earlier this year and could result streams drying up sooner than on most other dry years.
• Water uses are at near record highs due to the extended dry weather and the need to sustain plant growth during the active growing season. In some area such as the Boyne River where water usage is very high, competition has developed for the limited water available in the river. It may be necessary for users to take turns pumping water so the demand does not exceed what the river can supply. Outflows from Stephenfield Reservoir have been set according to a sustainable yield using a rule curve based on past records.
• Water supplies for towns and villages are not in jeopardy this summer as they are based on relatively reliable sources of water.
• Groundwater levels are generally very good due to the high recharge last summer and this spring. Groundwater levels generally decline more slowly than surface water with the exception of some shallow aquifers. If dry weather continues, some wells located in shallow aquifers with high usage may not be able to supply sufficient water this summer due to heavy pumping. In addition some shallow wells sustained by nearby streams may run dry later this summer if the stream dries up.
• The main concern with respect to water supplies is the possibility that the dry weather may continue through the autumn and winter. If there is a poor recharge in the spring of 2007 and the drought continues next year, there could be serious water supply problems next summer.
• While surface water supplies are still generally good, water conservation is recommended since the length of the dry spell cannot be predicted with reliability and conditions will deteriorate if the dry weather continues.
• The Environment Canada long range weather outlook suggests above average temperature and below average precipitation to continue into the autumn. However the Canadian Centre for Climate Studies indicates that conditions will change to below average temperatures and above average precipitation this autumn.

Hydrologic Forecast Centre
Water Branch,
Manitoba Water Stewardship