This is really useful information that we should not forget.
Minor point: A lake MIGHT be a kosher mikveh, but it would take special expertise in both halachah and in geology/hydrology to determine if it is, and that status can change during the season. The post’s advice not to ever assume that a lake is a kosher mikveh is well taken unless you can find a rabbi who is an expert in both who has checked out the particular lake for the time you are intending to use it, or a rabbi who has a hydrologist on call who can check out the lake alongside the rabbi. (I’m actually unaware of any rabbi who fits such a description; does anyone know of any?)