Make sure you clean it at least once a week and change water daily. It will probably pose more of a problem then help. They do like to sit in water and waterfalls are so cool looking but if he poops in it, its a big mess to clean. It will only turn out to be a bacteria fountain before to long. I would just place a clean bowl of water in his cage daily if your worried about him getting water.
I soak mine in the sink daily and do not leave standing water in the cage.
I do love waterfalls. I had them in my cham's cages.