Some pond products, normally targeted towards larger ponds, may call out their product application rates based on parts per million (PPM) concentrations. If you are unfamiliar with how to calculate these rates for your pond, then the following examples should help illustrate how to calculate applications rates using parts per million (PPM) concentrations.
There are 2 separate examples for each of the 3 steps below, which are based on the units of measure for either acres or feet. Choose whichever unit of measure is best suited for your application.
Step 1: Calculate Water Volume
A. To Calculate Water Volume based on Acres:
Multiply surface area (acres) by average depth (feet)
EXAMPLE: I have a ½ acre pond with an average depth of 4 feet. I found my average depth by taking measurements in a regular pattern around my pond and calculating the mean of these readings.
Multiply surface area (1/2 acre or .5) by average depth (4 feet). ANSWER: My pond has a water volume of 2 acre-feet.
B. To Calculate Water Volume based on Feet:
Multiply surface area (feet) by average depth (feet)
EXAMPLE: I have 100’ x 109’ rectangular pond with an average depth of 4 feet. I found my average depth by taking measurements in a regular pattern around my pond and calculating the mean of these readings.
Multiply surface area (100’ x 109’) by average depth (4 feet). ANSWER: My pond has a water volume of 43,600 cubic feet.
Step 2: Calculate Weight of Water to be Treated
A. To calculate weight of water to be treated based on Acre-Feet:
Multiply volume (acre-feet) by 2,720,000
EXAMPLE: Multiply volume (acre-feet) (calculated in Step 1A) by 2,720,000.
Multiply volume (2 acre-feet) by 2,720,000. ANSWER: Weight of water to be treated is 5,440,000 lbs.
B. To calculate weight of water to be treated based on Cubic Feet:
Multiply volume (cubic feet) by 62.44
EXAMPLE: Multiply volume (cubic feet) (calculated in Step 1B) by 62.44.
Multiply volume (43,600 cubic feet) by 62.44. ANSWER: Weight of water to be treated is 2,722,384 lbs.
Step 3: Calculate the Amount of Product to be Added
To calculate amount of product needed based on Acre:
EXAMPLE:Multiply the weight of the water (Step 2A) by the recommended concentration (shown in product instructions). Since recommended concentrations are normally given in parts per million (PPM), we need to convert the value in parts per million to a decimal equivalent. So 2 PPM is the same as 0.000002 when used in this calculation. So based on our acre’s example:
0.000002 x 5,440,000 = 10.88 lbs of product is needed
To calculate amount of product needed based on Cubic Feet:
EXAMPLE: Multiply the weight of the water (Step 2B) by recommended concentration. Since recommended concentrations are normally given in parts per million (ppm), we need to convert the value in parts per million to a decimal equivalent. So 2 ppm is the same as 0.000002 when used in this calculation. So based on our acre’s example:
0.000002 x 2,722,384 lbs = 5.44 lbs of product is needed