Is 10 acres your total watershed for the pond and is what your estimating?
If your math is right, and then say plug in 100 acres for a watershed it adds up fast. But there are a lot of variables, like how fast does that rain come down and soaks in or not, what grade of hills you have, and soil types, etc, etc. I am sure there is an agency that can help you figure all this out for your particular location.
