Something about Mayo Lake

It is time that Mayo Lake was examined for its salmon habitat potential and not just for its hydro electrical generating potential. Situated in the heart of the Yukon, Mayo Lake is very roughly equidistant between the communities of Mayo and Keno.

It is time that Mayo Lake was examined for its salmon habitat potential and not just for its hydro electrical generating potential.

Situated in the heart of the Yukon, Mayo Lake is very roughly equidistant between the communities of Mayo and Keno.

It has a surface area of about 95 square kilometres.

On the map it looks like a sideways Y, consisting of the long left arm running east west, with the right hand part of the Y breaking off halfway along and running southeast.

The lake itself has, for the most part, steep sides from which a number of streams tumble.

A few streams have viable placer mining operations on them.

The watershed of Mayo Lake is small, probably no more than about two and half thousand square kilometres.

The lake is on what can be very loosely termed a massif, a geological upswelling from the surrounding terrain.

This massif includes portions of the Gustavus Range, the highest peak being Mount Hinton.

No major rivers drain into Mayo Lake; instead, they flow around it either into the Stewart or Mayo river systems.

There is a small dam at the west end of Mayo Lake which acts as a control structure on the amount of water that can leave the lake and enter the Mayo River.

This permits Yukon Energy to control the water flow feeding the Mayo River and thus into the Wareham Dam.

The Wareham Dam is about 50 kilometres downstream and is where the hydro generating station is.

Somewhat confusingly, it is referred to as the Mayo hydro station, even though it is not on Mayo Lake.

Both the Wareham and Mayo Lake dams were built back in the early 1950s.

This means both lakes and the connecting river have had half a century to adjust to a new ecological regime.

And quite an adjustment it has been.

The written historical record does show that prior to the dams being built salmon migrated all the way up the Mayo River, into Mayo Lake and spawned.

The construction of the dams halted that. Back then fish ladders were not installed.

Where the salmon spawned is a matter of guesswork, but the wetlands at either end look most promising.

Of particular note is the Roop Lakes, a fascinating complex of swamps, lakes, and streams at the extreme east end of the northern arm of Mayo Lake.

The reason this is mentioned is because the Yukon Energy Corporation is thinking of adding further hydro-electrical turbine structures at the Wareham Dam facility.

This project is known as Mayo B.

Estimates of how much the project will cost are over one hundred million dollars.

One of the results of Mayo B could mean playing around with the water levels of Mayo Lake to provide adequate water flow in the Mayo River to power the additional turbines at the Wareham Dam.

This will have an impact on the riparian habitat of Mayo Lake.

Any project this size usually considers the possibility of including mitigative measures to offset any possible ecological harm the project might cause.

If the Mayo Lake levels are altered, the ecosystem which has taken 50 years to adjust since the dams were built, could be affected.

But a possible mitigative measure could be to bring the salmon back to Mayo Lake.

It might be time to install fish ladders over both the Wareham and Mayo Dams and get a hatchery going.

Now this is not going to be easy nor is it going to be cheap.

Wareham Dam is the tallest dam in the Yukon, about 32 metres high.

Getting a fish ladder over that is not impossible, but it would certainly be challenging.

The Mayo Lake dam is much easier to do, being only about five metres high.

If a huge amount of public money is being flung at hydro generation projects such as Mayo B a proportional amount could be used to enhance the ecosystem it will affect.

The installation of fish ladders would enhance salmon spawning areas, although it would also require a Mayo Lake hatchery.

Given the current catastrophic state of salmon stocks every little bit of enhancement would help.

This enhancement would mean restoring access to a portion of historical salmon habitat and by establishing appropriate hatchery operations

Hydro power is not necessarily green, despite what certain politicians and even environmentalists say.

The loss of Mayo Lake as a salmon spawning area in the 1950s shows that.

The Mayo B project should includes a means to restore access to some of those spawning grounds.

The ecological damage done in the past could then be partially mitigated.

Lewis Rifkind is a Whitehorse based

part-time environmentalist.

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