How to Calculate the Correct Filling Pump for a 1-Acre Pond

Filling a large pond can take considerable effort and time. A 1-acre pond that is only 4 feet deep has a volume in excess of 1 million gallons. Filling this size of pond with a domestic pump designed for a well could take weeks, if not months. When there are time limits on the duration of the refilling, you need to establish the minimum size of the pump required. Computing this involves some basic math.

Calculator
Long graduated stick or rope
Pen and paper

Instructions

- 1
  Establish the average depth of the pond by lowering a weighted rope or graduated stick to the pond bottom at intervals across it. Add together the measured depths and divide by the number of measurements to find the average. For example, with four measurements of 1, 1 1/2, 1/2 and 2 feet in depth, the average depth is 1 foot.
- 2
  Calculate the volume of the pond by multiplying the surface area by the average depth. (An acre is equivalent to 43,560 square feet.) The volume of the pond is the surface area times the average depth, so a 1-acre pond that is 2 feet deep has a volume of 43,560 X 2, or 87,120 cubic feet.
- 3
  Determine the length of time permitted to fill the pond. Pumps are rated by the number gallons they move per hour. The time available for filling the pond determines the size of the pump needed. Convert cubic feet to gallons by multiplying by 7.48051, the number of gallons in 1 cubic foot. For example, a pond containing 87,120 cubic feet of water also contains 651,702 gallons.
- 4
  Divide the number of gallons by the length of time available for filling the pond. This gives the capacity of the required pump. Filling a pond containing 651,702 gallons over 10 days requires a pump moving (651,702 /10 X 24) gallons per hour, or 2,716 gallons per hour.

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