Wednesday, March 23, 2011

Wetland draining, flooding, and nutrients: Save My Lake

"Save My Lake" is a documentary about the environmental issues surrounding Lake Winnipeg. It airs on April 3rd at 7PM on CBC.

As long as Manitoba has been colonized, for agricultural purposes our land was drained. Before this, the prairies and especially Southern Manitoba, were covered by prairies, wet meadows and wetlands.

This is a part of the natural history of our land that is largely ignored. The environmental impact of this activity is enormous. How enormous? Oak Hammock Marsh (which had it's first Canada Goose sighting on March 13th!), which you can get to after a short 20 minute drive north of Winnipeg, covers just 36 square kilometres, a paltry 8% of it's original 470 square kilometre area.

Apply this activity to all throughout the Red River Valley, up into the interlake, west to Lake Manitoba and Dauphin, and well...where does all the water go?

As spring is nearly upon us, snow starts to turn into rain, lakes appear on driveways and the city wages war on potholes, the first flood predictions come out and we collectively hold our breath to see how bad we're going to get it this time. For Lake Winnipeg, the spring melt and flood season mean all that agricultural runoff from the watershed region end up in the lake.

Putting my diagram-drawing skills honed by six years of formal education to the test, I'll try and make the science/environmental aspect of what this means a little easier to understand.

Water moves from left to right.

Here, spring melt ends up in a low-lying area or wetland, slowing the flow of water and nutrients. Runoff and silts settle in a wetland, which are themselves nutrient “sinks,” that is, a place where nutrients gravitate to.

If that is a “before” scenario, the “after” scenario is that the wetland is replaced with a drainage ditch, allowing all the water to flow freely and quickly to the nearest river.

Which is what we largely have now.

Wetlands are a key part of reducing the swelling of nearby rivers in springtime, and also catching nutrients before they can flow unabated into Lake Winnipeg. The nutrient that is present in large quantities in agriculture of course is phosphorous, which comes in the form of phosphorous-based fertilizers.

In the film a scientist from Ducks Unlimited states that springtime runoff can have phosphorous levels as high as 1-2 milligrams per litre, which is comparable even to some sewage effluent. If this can flow unobstructed directly into a river, it can travel hundreds of kilometres and eventually end up in Lake Winnipeg.

Programs are in place now to encourage keeping existing wetlands in place, or returning farmland that used to be a wetland, back into one. These programs and recreating wetlands and streams will prove to be essential in improving the environmental health of our lakes and rivers.

I highly urge people to go see Oak Hammock Marsh. Either now, to see returning migratory birds, or in the spring or summer. You don't even have to worry about mosquitoes (I'm not kidding!) There's more than enough to keep you going back, more than 30 kilometres exist for your exploration and the interpretive centre and website provide a ton of information.

So once again, the documentary airs on April 3rd at 7PM on CBC. You can join the Facebook group for the panel discussion and film viewing.


Ed said...

Thought you might find this interesting. It's sorta related...

Don Mitchell said...

How about you Winnipeggers lobby the provincial and federal government to reward land owners who attempt to retain their wet lands? Right now most farmers will plant corner to corner if they can to maximize the return from their land. Also with the size of equipment they save a lot of fuel and chemical if they do not have to go around sloughs and potholes.
Also don't blame all the problems in Lake Winnipeg on Agriculture. I am sure that the city of Winnipeg contributes enough on its own.

Graham said...


1) We don't need to lobby because there is already a program in place. I said that in my post. I suppose you read that part.

2) I come from a farming family. I can tell you 100% that no farmer goes out on his field thinking "I can save gas if I thresh like this."

3) All agriculture from here, to the Rocky Mountains, contributes. So yes, farming has a lot to do with it. A lot more than any one city in particular.

4) Spring runoff contains levels of nutrients and phosphorous pollution equal to or greater than sewage discharge. That is also in my post.

5) This is only one entry in a series. If you want to see the rest, find the "Save my Lake" tab at the top of my website.

Graham said...

@ Ed

Interesting. I would say, "of course they did." And then I would say "but there weren't some 2 million-ish native americans living on the prairies."

All land drainage issues we have today is directly attributed to us.

Ed said...

I would hesitate to make any assertions about population numbers pre-euro. Wade Davis has remarked that European accounts of the American indigenous populations often drastically underestimated the amount of people as a way of marginalizing them.

I think the land drainage issues are due to our approach to "nature" in general. The idea that we are somehow apart or above "nature" when in fact we are one in the same. We can have a positive effect or a negative one and this is primarily a result of how we view this relationship.

Graham said...

Absolutely Ed. Good points.