This is fucking stupid. I have lived around this area for my entire life and literally everyone who doesn’t live on a reserve (and isn’t part of an actual town) have wells or cisterns that were paid with privately.

The only thing stopping someone from getting their own well would be if the ground water isn’t available (very low probability that everyone around the reserve has ground water but the reserve doesn’t) or that the ground water is contaiminted (also very low probability for the same reason as before, and especially because contamination that bad would have a huge affect downstream in the Grand River).

If someone could explain why wells and cisterns don’t work on this particular reserve I’d really appreciate it.

I would assume it is because the Federal Government is responsible for water on the reserve, which is pretty standard information in Canada, and those living on the reserve don't have the authority to privately install anything.

I am happy to hear that you and your neighbors have the means to privately install personal well's and cisterns on your property, but this is clearly a different situation.