Consider depth and size seperate isues. Depth is not a factor in acerage. Depth is also not considered in stocking rates, just surface acers. To calculate the total volume of water you can multiply the surface acres by the average depth to find how many acer-feet of water you have, then multiply acer-feet by 326,000 to find total gallons. If you need to know cubic feet instead of gallons you can multiply acer-feet by 43,560 to find total cubic feet.
Just to reiterate:
surcace acres x average depth = acer-feet
1 acer-foot=326,000 gallons=43,560 cubic feet
7.5 gallons=1 cubic foot

-Scott

Take great care of it, or let someone else have it.