Well, in the drainage that's coming off the land in Winnipeg, the amount of nutrients coming to Lake Winnipeg will be a relatively minor proportion from land drainage in the city.
However, when you have a naturalized wetland, a lot of nutrients are being filtered out at that stage. They're being taken up into the plants. The retention that's going there is actually removing nutrients. In terms of Winnipeg alone it's probably a small impact, but if it is translated to a larger landscape, it could be significant.