I had to fill mine in order get the initial "jump" on it, but I had enough overlap with the extra rubber that rainwater will collect...ever so slightly. After my initial fill, I didn't have to do much adding. Shallow water is definitely mosquito heaven. My plan, which seemed to work, was to dig narrow and deep. That kept the water cooler and darker to try to cut down on algae and mosquito. There are also no-toxic "dunks" that you can throw in there to keep the mosquitoes at bay. If you can find a way to get run-off to fill from time to time go for it! The ground I'm in is a little too uneven to make any one spot better than another for run-off.
Number 1 google search! Thanks Neal! I'm thinking about building one that natural rain fall and run off will fill. Is a liner necessary to hold the what. We have quite a bit of top soil but its all lime stone underneath.
Being you and Neal are both in MN, be careful with what you're doing; a phone call or visit to your local NRCS would be highly recommended in my opinion.
This pond would be in Iowa. There is no existing creek bed where I'd like to place it. It is a low spot in the woods that rain water runs off down the hill side.
