Irregular Shape Pond Volume

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With simple shapes, multiplying surface area by depth gives us volume.

Most ponds, however, are not simple shapes, so they need to be broken up into several different calculations. The first step is to work out the surface area of the whole pond.

By dividing the ponds surface into shapes, you can work out the surface area for each shape and add the results together to get a surface area for the whole pond


Step 1 - Surface area

The surface of most ponds can be measured as several different shapes. From these measurements you can work out the surface area of each shape and add them together for a total surface area for your pond. pond area diagram

Trapezoid surface area

trapezoid surface area Area = C/2 x (A+B)
Distance A (cm)
Distance B (cm)
Distance C (cm)

Your Surface Area is
CM²

Rectangle surface area

rectangle surface area Area = (AxB)
Distance A (cm)
Distance B (cm)

Your Surface Area is
CM²

Circle surface area

circle surface area Area = (Pi Π x r2)
Radius

Your Surface area is
CM²

Triangles surface area

triangle surface area Area = (AxB)/2
Distance A (cm)
Distance B (cm)

Your Surface Area is
CM²

Add together all your pond surface area measurements to give a total area.

Step 2 - Average depth

Now you have a surface area figure, you need a depth figure to work out volume. If your pond has a flat bottom with no ledges and steep sides, you can just use the maximum depth.

If your pond has an uneven, undulating depth with gradients or ledges, you will need to work out an average depth figure to use.

To work out average depth divide your pond into a grid and measure the depth of each area. If you add all these areas together and divide by the number of areas measured, you will get an average depth.

average pond depth

Add together all your depth measurements and divide by the number of measurements taken to obtain your average depth. E.g. for 6 measurements (M): (M1+M2+M3+M4+M5+M6) ÷ 6 = Average Depth


Step 3 - Volume

Enter your total surface area (cm²) and average depth (cm) below to obtain your pond volume

Total surface area: (Av) Depth:

Your pond volume is:

Litres Imp Gall US Gall


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