In 1905 when the treaties were signed there was no water boil advisory and there sure as hell wasn't any advisory before the white man showed up. I have consumed unboiled lake and river water in northern Canada for many years and never gotten sick from it. I am sure the same can be said for the natives that have lived up there for thousands of years. Of course if you want to 100% sure that you will never get sick then by all means boil the water.