The Canberra rainfall pattern is very interesting…
- the 30-year average rainfall is 629mmm/yr.
- over the 3 years of the worst drought in living memory, 2001-2003, the rainfall average was still 525mm/yr. only a 20% drop.
- there is more rainfall during the 6 hottest months than during winter.
Here’s how to calculate how much water you can collect from your roof. Take the number of square metres of roof, muliply by the number of millimetres of rainfall, to give the number of litres. e.g. If you have 150 square metres of roof, and the average Canberra rainfall is 525 mm, then you could collect over 78,000 litres a year. A 10mm rainfall would yield 1500 litres! In both cases, it’s safest to subtract 10% to allow for absorbtion, evaporation etc.
For your information, here is the official Canberra, ACT monthly average rainfall graph, together with the average number of rain days, supplied by the Bureau of Meteorology.
Thinking about a water tank- your own, personal water supply? Visit our Water Tanks for Canberra page