I STRONGLY oppose the Canal right now.
AN has basically told us it would be on par with the Triangle Canal in cost, which means something like TEN mains, and on the order of 30 Econ.
I say "thanks but no thanks".
Do you know what else we could get with that much resources? Well, one option would be to get our Watchtowers to 100% and our roads to 100%. The watchtowers would require something like 6 mains + 1 secondary and 7 econ, given that they were at 35%. Our roads will require the rest of the actions, since they should be at 11/18 coverage or something like that; they were at 7/16 at the end of Fun And Games, and we built more Trails in More Fun And Games (+1), and Decision Point (+1), and are about to Main them (+2) with the winning vote, but we added a province so I suspect that increased our cap by 2; thus, we should be at 11/18 now, and 3 Mains + 1 Secondary + 7 Econ will be enough to pay from everything.
Another option would be to take the Expand Forest Main ten times. Note that each use actually produces a net of 1 econ and 1 LTE (at 3+ cities, anyways), so that would produce resources instead of consuming them, give us sustainable forests for the near future,make our lands much less susceptible to invasion, let us sell bulk lumber/charcoal, and probably invent any number of things (this is ten main Study actions we are talking about, here!).
Point being. Say no to Canals. We have better things to do.