If you could shield the waterfall from feces from the chameleon and insects dying in the water, and still have the chameleon reach the water to drink, yes.
Real world: no.
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Unfortunately Nick is correct that waterfalls are a veritable smorgasbord for bacterial contamination. I started out with a dripper and made a sort of ring using 1/4 inch soaker hose tubing to provide a larger area of water for drinking. I never hand misted the enclosures but bought a Monsoon automatic mister. It was a piece of crap and I wish I would have just spent the extra $40 or so and got a better system. I ended up getting an Aquazamp with a raindome. My chameleons hated when the Monsoon would spray their cages but after getting the Aquazamp they loved getting sprayed. I think it was because it was a finer mist. The only reason I got the Aquazamp over mist king is the pump could support a greater number of nozzles. They are both quality products.