What’s with the weir? Depends on who you ask

Joe McWilliams
Lakeside Leader

The weir on Lesser Slave River has been the subject of endless debate over the years. Ever since the Government of Alberta installed it in the late 1970s (or maybe early 1980s), it has been controversial.

When the lake is too high, it is blamed. When the lake is too low, it is also blamed.

There have been endless calls for it to be improved. Making the entire thing adjustable would solve the problem, most commentators seem to think.

Back in the 1990s, the idea of installing some kind of flow control was debated down to the finer points. Gerry Allarie – then the mayor of Slave Lake – was involved. When it came right down to it, he balked.

“Who’s going to control it?” he asked, memorably, at one meeting. “Not me.”

Allarie was anticipating a scenario where adjusting the level of the weir (and therefore the lake) would be about equally welcome and unwelcome by different interest groups. And he didn’t want the Town of Slave Lake to be in the middle of that battle. So the effort to lobby the province to do something was shelved.

The government did install a small gate on the north side of the weir complex a few years ago. It has been doing its part lately, allowing more water through. But in the big picture, it doesn’t appear to make a lot of difference. In any case, it was installed more as an aide to fish migration than to help with water levels. When fish are moving upstream during the spawning season it is open; after that it is closed. Its other ostensible purpose is to allow more water through when river flows are getting dangerously low. Dangerous, that is, to the maintenance of aquatic life downstream. Several times in the past two or three decades, flow over the weir has all but stopped. Since downstream industrial users of river water depend on a minimum volume of water in the Lesser Slave, this was a matter of some urgency.

The weir was part of a two-phase project to moderate the extremes (high and low) of the lake. The other part was to straighten the river downstream from the weir, so as to speed the flow. The river used to meander all over the place for the first several kilometres; draining the lake was a very slow process, leaving a lot of unhappy farmers along its margins in high water years. Straightening helped this, and the weir would provide a brake on lake-draining in lower water years, ensuring a minimum level higher than it had been historically in times of drought.

According to government hydrologists – the purpose has been and is being served.

The Leader posted photos of the weir on its Facebook group recently, provoking some interesting responses. One was from a former town councillor and member of the Lesser Slave Lake Watershed Council.
“From what I understand, it was the best shot at balancing flow, user requirements and cost, including maintenance. I would love to see a fully electronic gate system that could raise and lower the entire section of the ‘dam’ and could be programmed to react to events and seasons etc. The arguing that would ensue over what level the lake should be kept at would start a civil war. So what we have is best. It’s not stopping much water from going over right now anyways. The river systems downstream are full as well so even if we had no weir right now… the flow rate would not be substantially higher in my mind.”

The weir more recently, invisible due to this summer’s high water.
How low it can go: occasionally water stops flowing altogether.
The Lesser Slave River weir in a year not like this one, serving its intended purpose (or one of them) in keeping the lake from getting too low.

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