Still new at this, but it depends on ground cover as well as slope. I had 40 acres of timber draining into my proposed site and I was told 1.5-2 acres. If it is a linear relationship, that means you could go up to 7.5 or 10 acres for that 200 acres of drainage. For example, if we get 3 inches of rain, which is not uncommon where we live, most will run off and the runoff would put 3-5ft of water into a 10 acre pond. A 1 acre pond would go from empty to overflowing with that one event. Theoretically a 1 acre pond would have the water level increase by 30-50 ft if it had the capacity! I am sure somebody will chime in with more knowledge than me.

Water dries, rocks crumble, and trees die. The only thing that is eternal is the reputation we leave behind.
- Ancient Viking Proverb