Well, waterfalls are not really recommended in chameleon enclosures. Preferred methods to provide water for a chameleon are by misting them, or providing a dripper in the cage (usually a container of water that allows water to drip onto a plant inside the cage).
Both of these methods require that you have some sort of drainage strategy within the cage.
If your cage was properly drained, then the water spilling out of the waterfall wouldn't be too much of a problem.
The reason waterfalls are not recommended is because the water that pools at the bottom of the waterfall can be a breeding ground for harmful bacteria within the cage (particularly with the warm temperatures in a cage).
If you keep it spotlessly clean (i.e. recycling the water and cleaning the bottom pool daily) you won't have a problem. However this is more effort than it is worth, because if you are misting the cage properly, your cham probably won't even be drinking from the waterfall.
The bacteria problem applies to all pools of standing water - this is another reason why chameleons are not give bowls of water to drink from (besides the fact that most of them won't even drink from the bowls).
You don't mention what species of chameleon you have, but for most of the common species a night heat lamp is not required. Chameleons benefit from a drop in temperature at night (just like they would get in nature). It is recommended that the cage temperature drops by about 10 degrees (F) at night. You will only need the night heat light if you live in a really cold climate where the temperature in the cage would regularly and for long periods drop below 60F (some species can tolerate colder).
Howdy,...If I get a mister or a dripping system, do I still need a draining system? Thanks!
Yes, to keep this from happening take it out, put it in the box it came in and return it to PetsMart. It is not necessary, and in fact dangerous to your chameleon. Run a search for more info.