Yes to what Bob-O says. We have a 1/2 acre pond, and IMHO it turns out to be a perfect size for swimming and fishing casually. 1 acre is a large pond to maintain, especially when you consider you need to weed the edges of small trees and cat tails. The hole will look absolutely huge once excavated, and then you will realize how much water that really is!

Importantly how are you expecting this pond to fill? In many places it is ideal to have a pond in a low area that runoff will go to. You may wish to have some work done to direct water to the pond to help fill it, and have some water exchange.