Hersh,
Another factor to think about is evaporation rates. In Iowa, when you get 36 inches of annual precip over ten acres, some percentage of that will be runoff. Like the guys above say, the kinds of soil and plants determine the percentage of runoff. I've seen land where 100% is runoff, coming off mountains and rock and I've seen it where less than 20% is runoff, because a big percentage of the watershed is sandy and the water percolates downward fast and recharges an aquifer below. You are probably somewhere in the middle. Your NRCS folks can help you with that calculation.
For example, if you are in farmland with good topsoil and heavy clay subsoils, you will receive probably 40-50% of your 36 inches of rain yearly as runoff. If that's the case, you will get 14-18 inches of runoff over 10 acres. That's 140-180 acre inches per year, or roughly 12-15 acre feet yearly. For a one acre pond that averages 6 feet deep, you get at least double the amount of water that you will need. To that end, you need a good spillway to handle flooding rain events. And if you get an average of 40-50 inches of evaporation/sublimation each year, you still have enough runoff to fill your pond. But, you will have fluctuations during part of the year. Your pond will likely drop two feet from time to time. Plan for that.
Good questions. Post again.
FYI, I don't always have time to read through the entire forum, so if you need some clarification about something we wrote in the book, drop me an email at pondboss@texoma.net and I'll respond much more quickly.

Teach a man to grow fish...
He can teach to catch fish...