Winnipeg Free Press - PRINT EDITION
Pump system could sort water woes on Lake Manitoba
The Edmonston pumping station in southern California is an engineering marvel. It is part of the California aqueduct system that gathers water from the northern half of the state and delivers it to thirsty millions in the south. It pumps 4,400 cubic feet of water per second. That is not remarkable. What is remarkable is that it lifts this water 600 metres over the Tehachapi Mountains.
The current flood on Lake Manitoba has arisen because too much water is entering the lake with too little of it leaving. The Portage Diversion has redirected most of the flow from one watershed, the Assiniboine River, to another, Lake Manitoba. The predicable result is a second flood in four years. Even under the best case, the lake will spend months at flood level and fall gradually during the winter. It will be high next spring and poised to flood again.
The provincial government claims the emergency channel on Lake St. Martin is a solution to this flood problem. It is not. It is a solution to flooding on Lake St. Martin, which is useful and needed.
The only near-term solution to the problem of continued flooding on Lake Manitoba is a new outlet. There are substantial engineering challenges, not the least being the slight elevation changes on the landscape. We are, after all, on the Prairies. A major problem on Lake Manitoba is that outflow falls sharply with lake level.
Lake St. Martin, the most likely destination for the water is, at its nearest, nine kilometres away but only three metres lower.
There is another natural outlet to the lake: the Assiniboine River. It just isn't used much. The last time was in 1882 in a flood a bit higher than 2011. Water left the south end of the lake following the Long Lake Drain back to the lower Assiniboine. Here the elevation change is roughly six metres over 30 kilometres, thus, using gravity to get water out of the south end of the lake is a challenge.
But there is another solution: Pump the water. The California aqueduct system provides a shining example. There, water is lifted 1,000 metres and pumped 400 km. We needn't be nearly so ambitious. At Fairford, water might need to be pumped perhaps one km around the existing dam and lifted three metres. Alternatively, a pump station at the south end of the lake would need to lift water maybe four metres and pumped 30 km. Kid stuff compared with California.
Moreover, both Fairford or Long Lake pump stations could get water out at lower levels, solving the critical problem of low flows at low lake levels.
A Fairford pump station would require expanding the Lake St. Martin emergency channel to accommodate extra outflow. That can be done in weeks.
The greater challenge would be addressing the legitimate concerns of First Nations near Lake St. Martin. They have long-standing issues going back to the construction of the Fairford Water Control Structure in 1961, the Portage Diversion in 1970 and the emergency channel in 2011. These have generated chronic flooding that has affected fish and wildlife. These issues cannot continue to be ignored.
A Long Lake pump station would need to get water to where it can flow downhill, perhaps a distance of five km. It would serve primarily as a fall/winter exit allowing increased outflow for up to eight months a year.
The median flow on the lower Assiniboine falls to 1,000 cfs in August and remains low until April. The upper decile flow is just 3,000 cfs in August and remains low until March. Thus, an extra 5,000 cfs could easily be added to the Assiniboine over the low-water period without harm. If used over an eight-month operating period, that drops Lake Manitoba two feet.
Increasingly frantic residents around Lake Manitoba clamour for a new outlet to provide flood relief. Provincial officials have rebuffed these demands. We are told we can attend an open house this fall with conceptual drawings of a new outlet that might or might not be built in the future. That time will not be soon. Under current spending plans nothing will be built before the early 2020s. Speaking for my fellow Lake Manitobans, Premier Selinger, that is not nearly good enough.
Provincial officials provide three reasons for why an emergency outlet is impossible.
First, there is bedrock where an outlet might be located. This is true near Fairford, but is it true at Watchorn Bay on Lake Manitoba? It's certainly not a problem at the south end of the lake that is an alluvial floodplain (dirt). A channel could be dug there with a plastic beach shovel.
The second reason is that an outlet could cross First Nations land. Clearly First Nations would -- and should -- hold a veto over such construction. The long-standing and legitimate grievances need to be resolved, full stop.
A southern exit (Long Lake Drain) does not add to the existing problems of First Nations communities.
The third reason is money. In 2011, cost estimates were prepared for outlet channels at both the north and south ends of the lake, ranging between $250 and $350 million. That stacks up against flood damage of well over a billion dollars in government expenditures, several hundred million more in out-of-pocket costs to flood victims, and $1.3 billion in damages from pending lawsuits. Moreover, if built under emergency conditions, it is cost-shared with the federal government under favourable terms. A Lake Manitoba outlet is on sale right now.
And our PST increase was justified on the basis of the need for new flood infrastructure.
There are two types of people in this world. The first are those who focus on why something can't be done. You need to get rid of them. Then you work with the people who focus on how something can be done.
Scott Forbes is an ecologist at the University of Winnipeg.
Republished from the Winnipeg Free Press print edition July 15, 2014 A9
Have you found an error, or know of something we’ve missed in one of our stories?
Please use the form below and let us know.
Having problems with the form?Contact Us Directly