I'd like to make a little natural pond, maybe a 40 foot diameter. It is going to be at the bottum of a small incline, so i'm thinking it will catch some run off. Also, the pipes from the gutters on our house are right where the pond is going to be, so i was thinking they can run some water into it from those pipes (when it rains). I plan on renting a compact bobcat excavator. Any advice would be appreciated.