Another outlet for Lake Manitoba

Hey there, time traveller!
This article was published 28/04/2015 (4019 days ago), so information in it may no longer be current.

Lake Manitoba lacks outlet capacity to prevent flooding: The solution is either reduced inflow or increased outflow.

Southwestern Manitoba up to and including Lake Winnipegosis has become susceptible to climate change impacts — “200-year floods” twice over the past four years — and increased farm drainage upstream sped the movement of water downstream. The Souris and Assiniboine rivers flooded, leading to disastrous inflows through the Portage diversion into Lake Manitoba, while high flows entered Lake Manitoba from Lake Winnipegosis via the Waterhen River, exacerbating the situation.

Assiniboine River flows required operating the Portage Diversion for extended periods. More than 35,000 cubic feet per second of water poured into Lake Manitoba in 2011, and about 29,000 cfs in 2014. In 2011, more than three million acres and in 2014 more than one million acres went unseeded. Five hundred thousand acres were drowned out in 2011, somewhat fewer in 2014.

Prairie areas further west were dry. Saskatchewan River flows decreased, leading to a 20 per cent decline in power generation at Grand Rapids.

Here’s the opportunity to address Lake Manitoba flooding problems.

Former premier Ed Schreyer has proposed water from Lake Winnipegosis be pumped north into Cedar Lake, entering Lake Winnipeg via the Grand Rapids hydroelectric generating station. Lowering the level of Lake Winnipegosis would reduce the flow into Lake Manitoba through the Waterhen River, offsetting inflow from the Portage Diversion over the spring and summer periods.

Calculations indicate pumping 7,500 to 10,000 cfs from the north end of Lake Winnipegosis through a six-kilometre channel into Cedar Lake for up to seven months during the open water season, would offset the inflow to Lake Manitoba, bringing Cedar Lake back close to earlier preferred levels. Some of this water might be spilled over the Grand Rapids spillway, but most would be available for power generation. Flowing at 7,500 cfs maximum capacity for seven months, this could potentially reduce the level of Lake Manitoba by about 2.75 feet, or about 3.4 feet at 10,000 cfs.

This option, at an estimated cost of $250 million, has clear advantages over the Manitoba government’s proposed $500-million channel that will only take slightly more than one foot off peak flood level. The pumping option is cheaper, more environmentally friendly, reduces impacts on First Nations and generates revenue.

The geology at the north end of Lake Winnipegosis is glacial end moraine: a mixture of gravel, sand and rocks deposited by glaciers as they periodically moved forward and receded. It lacks fine particles that could cause serious silting in Cedar Lake. Details on the slopes involved on land and under water will be needed to ensure appropriate gradients at the inlet and outlet.

The channel route proposed by the Manitoba government goes through very different geology: Fine particles picked up in the channel would enter Lake Winnipeg in large quantities, impacting fish habitat and water quality. Excess nutrients from the Assiniboine would also be transferred before there was much opportunity for upstream vegetation to sequester them. A Clean Environment Commission review for constructing such a channel would likely be required, further delaying protection of Lake Manitoba shores.

The Manitoba government’s route impacts five First Nations, total population about 71,000. Channel construction and operation will cause substantial disruption to their lifestyle and livelihood. In the context of the pumping proposal, Easterville on Cedar Lake is home to the Chemawawin Cree Nation and has a population of about 800. Water levels there will be within the range experienced previously when Saskatchewan River flows were more substantial.

Finally, the pumping option would require about 12 to 15 megawatts of power for the full seven months if the maximum pumping capacity were to be required in a given year. Capital costs would be included in the overall capital plan for the channel, bridge over it and pumps, but the additional energy produced at Grand Rapids (with a head of water of about 120 feet) would exceed the energy required by the pumps by a considerable margin. At full operation, the water pumped to Cedar Lake would add about 400 GWh of energy, or an additional 25 per cent to the average annual electricity production of Grand Rapids. On a system-wide basis, given that Manitoba Hydro produces 29,000 GWh of energy on average from its entire system, this maximum estimate for the increment at Grand Rapids would represent 1.3 per cent of existing capability, about 30 per cent of the annual production of the new Wuskwatim generating station: a facility that cost $1.8 billion.

The pumps may not be required every year, and not always for seven months. Grand Rapids operations might require some water be spilled in the spring. Given that the capital costs are considerably lower and the scheme would actually generate profits for Manitoba Hydro, Manitoba would be well advised to give this idea serious consideration. Manitoba would gain revenue from additional water-rental rates through the Grand Rapids generating station.

The Lake Winnipegosis pumping proposal is an efficient and environmentally beneficial solution to the Lake Manitoba flooding problem.

 

Jim Collinson is a management consultant specializing in energy, economic and environmental issues who has held assistant deputy minister positions in the federal and Manitoba governments.