Converting volume of water in your garden fish pond
Converting volume of water in your garden fish pond
The volume of water in your garden fish pond plays an important role in deciding upon correct size of pond pump, pond filter and pond ultra violet light. Sometimes you need to convert from different units
Know your ponds volume ... ie the volume of water it holds including the waterfall
Ideally a ponds volume should be measured accurately at the time of filling the first time. If not then the slide rule or something more modern must come out. Many countries allow the house owner to read the water meter. This is the ideal way to measure your ponds volume. Just dont let the kids use the bathroom while you are doing it.
In the table below you can see what the equivalent volumes are for different units
How to use this table You read across. For example 1.0 US gallons is the same as 0.8 Imp.gallon or 0.1 cu feet or 3.8 litres and so on. I have only shown 1 decimal point so do not fight me on absolute accuracy.
You will thus notice also that 1 cu metre is 1,000 litres or 35.3 cu feet etc
Volumes of Irregular Shaped Ponds
If your pond is not a simple rectangle or square the calculation is more difficult. If your are not totally accurate do not be too concerned because we are looking for an approximate volume. However you should aim to be within say 15% accuracy. In making approximations the simplest way to do this is to assume the pond is surrounded by a rectangle and then ask yourself what proportion of the rectangle is covered by water. See the sketch below to assist in understanding this measurement technique.
Lets say the proportion is 50% and the depth is once more constant at 0.5 metres and the rectangle around the pond is 3 metres long x 2.8 metres wide. The volume is calculated as follows:
3.0 x 2.8 x 0.5 x 50/100 = 2,1 cu.metres = 2.1 x 1,000 = 2,100 litres
If the depth is not uniform then use the average depth to calculate the volume.
Another more accurate approximation can be made by counting the small squares into which the pond has been divided as in the diagram above. This is the method explained in detail:
The pond was first drawn to scale using graph paper or something similar like a spreadsheet (this sketch was done on a spreadsheet):
Each square in the sketch has a constant size. As you can see the total squares covered in the total rectangular area is 11 x 12 = 132 squares.
The total yellow squares must now be estimated. I estimate about 21 full squares are covered by the yellow bits. If you get a bit different it does not matter much.
Now count the white squares I get 56.
This means you can now calculate the number of squares covered by the blue pond as follows:
132 21 56 = 53 squares
If each square is 0.2 x 0.2 metres then area covered by pond is as follows:
53 x 0.2 x 0.2 = 2.12 sq metres
If average depth of pond is 0.5 metres then pond volume is
2.12 x 0.5 x 1,000 = 1,060 litres
Knowing the volume of your pond is important if you want to specify other equipment correctly. Once again if you are not sure seek help.
While considering pond volume 1,000 litres of water is a good volume to hold about 1 kg of fish.
EPDM rubber is probably the best material for a garden fish pond
This web page is an extract from Tony Roocroft's "The Complete Pond Solver" ... you can read more about it at http://www.really-useful-books.com ... when you buy the book you get 12 Excel pond calculators free as well as "Water Lilies and Pond Aquatics" ebook also freeCreating your own garden pond using pond liner from EPDM or
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