At times I wish I had a little more runoff for my 3 acre pond, then a couole times a year I wish I had less. My pond has minimal watershed area and in fact my NRCS guy designed and we installed a terrace in adjacent field just so we would have more runoff.
I can not remember off hand exactly how much area we have but I'm guessing it no more than 25 acres and maybe no more than 20.
Thing is, we get about 42" rainfall a year and it is not uncommon to get two or three inches in a single rain. So at certain times we get a lot of runoff.
If you have a good NRCS agent, they should be able to help you.
post with pictures of water going over emergency overflow 
