I found a piece of land for sale that currently has a 1 acre pond. If I buy the land, I would want to increase that to about 4 acres. This pond is basically a dammed up ravine and I calculated the watershed to be about 120 acres, most of which is cropland. Is 120 acres enough to fill a 4 acre pond? I would want the 4 acre pond to have a max depth of at least 25 feet to control winter kill (northern midwest). My calculations tell me yes, but I'd hate to be wrong. What is the best way to determine this?