Adelaide’s average rainfall is low–around 520 mm a year.
The pattern is for a dry period from November to April, which receives a paltry 160 mm, with a wet season from May to October enjoying more than twice as much rain, about 360 mm.
For your information, here is the official Bureau of Meteorology map showing average annual rainfall (in mm) of Adelaide and areas throughout South Australia, as well as a chart breaking down Adelaide’s average rainfall by month.
How To Harvest Your Rainwater (and calculate your savings)
Throughout the country, water truly is the most precious resource we have, and it’s for that reason that so many clever Australians are setting up simple rainwater harvesting systems at their residences.
In these systems, roof guttering collects water runoff and directs it to water tanks. From that point, the stored water can be used to clean, irrigate the garden, wash clothes, or even filtered for potable household use.
In Adelaide, it definitely makes sense to stock up your water tanks well before summer arrives.
Just how much water can you collect from your roof?
Here’s how to calculate it:
Number of square metres of roof X the number of millimetres of rainfall = litres harvested
If you have 150 square metres of roof, and the average Adelaide rainfall is 520 mm per year, then you could collect over 78,000 litres a year (150 x 520).
Think about it–just a 10mm rainfall would yield 1500 litres! In both cases, it’s safest to subtract 10% to allow for absorbtion, evaporation etc.