There actually was a proposal put forward by the Canadian Wetland Inventory for a Canadian wetland inventory that laid out an entire approach on how to do this. It varies by region. In some locations of the country you don't need to get into that very fine detail, whereas when you get into the Prairies, you have to get down to a quarter-acre-size wetland. In other portions of the country, for example, in the boreal, you can have a lower resolution imagery. It depends on the types of wetlands you have.
On May 28th, 2013. See this statement in context.