It's a mathematical formula based on the lake's size and depth, as well as what different types of boats need to navigate on the lake. You combine all that information for all the boats to determine that a lake's carrying capacity is x number of boats. I can't give you the exact formula off the top of my head, but I wrote an article for Québec Yachting. It refers to all the studies that have been done on a lake's carrying capacity. That's one way to determine a lake's capacity.
On October 31st, 2024. See this statement in context.