Originally Posted by deltav

Yeah well..... it's still a big lake - plenty of places for an animal to poop in it, or for rotting things, whatever. Also people do live in the area. Sure, it's cleaner than most, but if you happen to have bad luck with any particular mouthful, very unfortunate things will happen. Our civilized guts just aren't conditioned for those microorganisms anymore. You can get giardia from mice, beavers, deer, etc, ain't just people.

I'd far far rather drink from a high-altitude snowmelt fed spring rather than a lake like that with so much surface area and shoreline, there's just too much access for something to contaminate it.