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Water Garden Pond Volume Measurement ... Use Surface Area and Average Depth

The basic principle behind pond volume calculation

The fundamental formula is simple .... the volume of any pond is the surface area multiplied by its average depth. However getting both these numbers correct can be a major challenge for most of us. The more accurately you know both average depth and surface area the more accurate your calculation of pond volume will be. If you have a pond and the depth is not constant you can make a very good estimate by taking a stick as was shown in the pond depth article here. In summary this entailed taking 10 different measurements to calculate an average.

Now that average depth is, all that is required to know the area of the pond surface. Lets assume the pond's surface is rectangular (few are in practice) the volume of the pond is,

width of rectangle x length of rectangle x average depth.

We have another article that we'll show you exactly how to get an excellent estimate of any shaped pond's surface area since few ponds follow regular shapes like squares, circles and so on. For the time being it's important to understand the principle since this applies to any situation.

If your pond is of equal depth and the same cross section then you can accurately measure the pond volume using your pond pump.

This method can only work when depth is constant and shape of pond is constant (it does not need to be a simple shape but it must be constant throughout the pond's depth)

Do the following ....

  1. Record the depth of the pond accurately before doing anything else and make a note ... record this to as close as possible to 1/10th of an inch or even 1 mm.

  2. Attach a hose to the pond pump and lead the hose to say a 5 gallons or 20 litre container.

  3. Fill the container to the known volume mark ... eg 5 gallons or 20 litres and take careful and accurate note of the time it takes.

  4. Do not switch off the pump and immediately pump water out of the pond for say 5 minutes.

  5. Record the depth after pumping out water fro 5 minutes.

The pond's volume is then calculated as follows:

  • S = depth of pond in inches or any unit before pumping starts.

  • D = inches or any unit of water pumped out of pond when pumping for the 5 minutes ... i.e. difference between start depth and final depth.

  • T1 = time to fill the container.

  • T2 = time pump was run to pump out water (eg 5 minutes).

  • V = volume of container.

Volume of pond = (S x V x T2) DIVIDED BY (D x T1)

Here's An Example:

  • S = 30 inches

  • D = 3 inches

  • T1 = 1 minute

  • T2 = 10 minutes

  • V = 3 gallons

Pond volume = (30 x 3 x 10) divided by (3 x 1) = (900) divided by (3) = 300 gallons

If the container was in gallons then thee final pond volume is in gallons. If the container was in litres then the final pond volume is in litres

It does not matter whether you measure depth in inches or any other units.

IMPORTANT

Use the pump to pump out water in the same position used to fill the container and keep pipe in same layout as when you filled the container. In other words aim for constant conditions of pumping.

 

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