Ranchers around Lake Manitoba worry the Manitoba government’s proposed new outflow channels won’t prevent them from being flooded again, as happened in 2011 and today. Some producers say flooding begins at 812 feet above sea level but the new channels won’t work well until 814.
The Western Producer sent the following questions to the Manitoba government, which are based on ranchers’ concerns. The answers are the official response of the provincial infrastructure and transportation department.
Q: Ranchers say flooding of Lake Manitoba begins at around 812 feet above sea level, yet the chart that is included with the department’s presentation on the proposed outflow channels describes 814 feet as flood stage. Does the provincial government believe that 812 to 814 feet is not a level at which flooding begins and is significant?
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A: 814 feet above sea level, wind eliminated, is considered the flood stage in which infrastructure such as cottages, homes and business are susceptible to damage.
By policy, the province does not provide flood protection to agricultural lands. The agricultural drainage network provides protection to crops from summer precipitation events during the growing season. The provincial drainage system and the provincial flood protection system does provide a degree of protection to agricultural lands from large spring and summer flood events, but the protection is not targeted to specific lands and does not provide full protection.
Q: The chart shows the upper limit of the operating range at 812.5 feet. Does the province plan to actively try to reduce the water level in winter and spring to be in the lower end of the range in springtime and early summer so that flood surges, such as those that occurred in 2011 and 2014, can be absorbed within the operating range rather than push them above 812.5 feet? In other words, what levels does the province hope to begin springtime with after a new outlet is built?
A: The long-term operating range of Lake Manitoba is 810.5 to 812.5 feet above sea level, wind eliminated.
The February 2013 Lake Manitoba Regulation Review recommended an interim operating range of 810 to 812 feet above sea level. The Fairford Control Structure (FCS) has been at maximum capacity since 2005, but due to this continued wet cycle it has been unsuccessful in controlling water levels to within either the interim or long-term operating range.
In the future, once the Lake Manitoba outlet (LMO) works are in place, both the FCS and the LMO will be operated to try and maintain the regulation range. Flood forecasting will provide strategic direction in operating the FCS and LMOs by anticipating floods and droughts that could cause Lake Manitoba levels to veer outside the operating range.
Q: Could the two proposed options for a new outflow channel allow the lake levels to be managed so that they were 810.5 to 811 feet at the beginning of spring?
A: The consultant’s advice is that the channel bottom or invert will be designed to be at 801 to 802 feet above sea level. This will allow the LMO to be operated below 810 to 812 operating range but at flows lower than the 5,000 to 7,500 cfs (cubic feet per second) design capacities.
The Lake St. Martin outlet channels are designed at 5000 cfs and 7500 cfs capacities at a Lake Manitoba level of 814 feet above sea level. Lake bathymetry (the underwater depth of lake or ocean floors) and shoreline configuration could further limit the outlet flow efficiency at levels lower than 814.
The LMO is just one piece of the puzzle for Lake Manitoba and provincial flood protection. The Assiniboine River-Lake Manitoba Basin Study is looking at numerous other options to provide better flood protection.
We are also looking at increasing the Assiniboine River design capacity to higher than the 18,000 cfs capacity experienced in 2011 and 2014. … Watershed planning, wetland restoration, preservation and protection initiatives and flood plain development controls are further tools to promote flood protection within the province. At this time, an open house on the Assiniboine River-Lake Manitoba Basin Study is scheduled for sometime in November 2014.
Q: Much shoreline degradation and native prairie damage have occurred in the past four years. Is limiting that kind of damage a policy consideration, or is that a likely byproduct but not a deliberate intention of the policies that will govern how the future outlet will be managed?
A: The province does not build flood protection works to protect agricultural lands. Nonetheless, the flood protection works as a byproduct do provide a degree of protection. Shoreline erosion is specifically identified as ineligible damage in the Government of Canada’s disaster financial assistance arrangements.
