Melbourne’s average rainfall is around 650 mm a year.
The pattern is remarkably even, with the lowest month (February) having 45 mm, and the highest month (October) having 65 mm.
For your information, here is the official Bureau of Meteorology map showing average annual rainfall (in mm) of Melbourne and areas throughout Victoria, as well as a chart breaking down Melbourne’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 Melbourne, your water tank can capture rainfall all year round.
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 Melbourne rainfall is 650 mm per year, then you could collect over 97,000 litres a year (150 x 650). And just a 10 mm rainfall would yield 1500 litres! In both cases, it’s safest to subtract 10% to allow for absorbtion, evaporation etc.