Agricultural drainage in eastern Saskatchewan is making it more difficult to operate the Shellmouth Reservoir in Manitoba, says a provincial official.
“What’s happening in Saskatchewan, there’s a drainage district right upstream (from the Shellmouth Reservoir) called Marchwell.… Their mandate is to drain land and maintain drains to improve their efficiency in moving water off the land,” said Steve Topping, executive director of Manitoba Infrastructure and Transportation’s water management and structures division, hydrologic forecasting and water management.
“Wetlands are being drained. They’re no longer a source of potential storage of water. Natural creeks are being channelized to improve the efficiency in which they (transport) water to the Assiniboine River.”
Overbank flow along the Assiniboine River has flooded an estimated 50,000 acres of cropland between Russell and Brandon this spring. This will be the fourth year of the last five in which flooding has occurred in the Assini-boine River Valley.
“Draining that wetland (in Saskatchewan) changes the volume inflow into the reservoir, and the channelization of drainage systems makes it (flows) much peakier,” Topping said.
“It’s been identified to the Saskatchewan government the impacts in Manitoba. We’ve tried to quantify them through numerous studies.”
In March, Manitoba flood forecasters said the risk of spring flooding on the Assiniboine was low. Farmers in the Assiniboine River Valley, with land now under water, have slammed the government for the inaccurate flood forecast.
Topping said the criticism isn’t justified.
“The month of April in the upper Assiniboine Basin was twice as normal (for rainfall) … twice the amount of average rainfall in that month than normally occurs. The March flood outlook was no longer valid.”
The province, in collaboration with a liaison committee, lowered the Shellmouth Reservoir over the winter to 1,389.5 feet to accommodate spring inflows.
Topping said lowering the reservoir to the operational minimum, 1,386 feet, wouldn’t have made a difference.
“I’ll stake my reputation on it, that volume of water was not significant enough to have any impact on reducing the flood peak downstream. The damages would’ve been still the same.”
Topping said continued drainage in Saskatchewan will exacerbate water management challenges in Manitoba.