Once grown, they do not need it, and I feel there are exceptions.
If it is really hot, water is very important. If it is really cold, being able to take in more calories is important.
I have a couple of solutions. One is to have an adjacent porch, covered in metal half inch hardware cloth (top, sides and bottom) with a sand floor covered with sawdust. The water and food go there. It's easy to clean up and the bedding in the duckhouse stays dry.
In winter, the ducks are in a different shelter so I have a watering station that is the bottom of a solid plastic dog crate. The water pot (flat bottom, straight up sides) sits on sawdust in that, and that keeps splash out of the bedding. The duck food is dry, so there is no mess from that.