You may or may not have heard of the GRAND Canal proposal. If nothing else, it deserves credit for its audacity. It was proposed by a chap named Tom Kierans, an engineer from Newfoundland who figures he knows how to solve the water problems faced by the American southwest and the Canadian prairies.
The idea is this: Kierans thinks that water could be drawn from Lake Michigan to supply the southwestern US, and from Lake Superior to supply the Prairies. To make up for this, though, we'd need to add more water to the Great Lakes, otherwise they'd eventually be drained. This is where Kierans' proposal gets... uh, interesting. He proposes building a gigantic dam to wall off James Bay from Hudson Bay, so that water from the rivers in northern Ontario and Quebec would be retained. Some outflow would be allowed at first, but no inflow from Hudson Bay, resulting in James Bay being turned into a giant freshwater reservoir. From there, the water would be diverted (and at some points pumped) into Lake Huron via the Harricana River, Lake Timiskaming, the Ottawa River, and the French River. Got that?
Of course, this sounds like utter madness. Even setting aside the environmental concerns (mixing watersheds is generally not good for biodiversity, and some have suggested that the resulting changes to marine currents in Hudson Bay could be harmful as well) the amount of effort, expense, and energy that would be required to do this is staggering. The idea has been floated a few times since Kierans proposed it in 1959, and was studied approvingly by some politicians, including Quebec premier Robert Bourassa and some guy named Brian Mulroney (remember him?) but fortunately these proposals haven't gone very far.
However, the idea is now being discussed again, in the mainstream media no less. Are they trying to soften us up for the idea? Certainly some, such as Gwynne Dyer, are saying that if we don't sell our water to the Yanks they'll just take it. But what if we don't build the GRAND Canal? Would the Great Lakes states stand for the lakes getting drained so that the southwest can keep their golf courses green and their pools full? I'd like to think not.
Of course, if it comes to that the US might resort to other means to get us to cooperate...