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How to Know How Much Rain Falls in Your Area

Rainwater harvested from the roofs provides a high-quality source of water to be used throughout your property for washing, toilet flushing and even safely consumed with proper precautions. When purchasing water tanks for storing rainwater, knowing how much water you can harvest may influence the quantity and size of water tanks you purchase.

This article is one in a two-part series to help you know how much rainwater you can harvest. In the previous article, we discussed  your capture area and knowing how much rainwater you can harvest. This articles looks at how you can find out the rainfall in your area.How to know how much Rain Falls in your Area

Estimating Your Annual Rainfall

First, you need to be able to find out how much rainwater falls from the sky in your area. Chances are you don’t have measuring cups outside and have monitored rainfall patterns throughout the year. Thankfully, Australia’s Bureau of Meteorology collects regional information on such. This means you can obtain a general estimate for how much rain will fall on your property throughout each season and month of the year. All you need to do is visit the rainfall section on BoM’s website:

Once there, follow these step:

  1. Select your “Period”. You can select any month of the year, season or annual rainfall.
  2. Select an “Area” (state).
  3. What follows is a map providing an average rainfall (millimetres) that has fallen over a standard 30-year period across your state. The colours indicate the how much rain falls in each region.

Such should be adequate for providing you with a good estimate of rainfall in your area.

Accurate Daily Rainfall Totals

While a rough estimate should be enough for most people, if you would like more precise rainfall data then you can also discover the daily rainfall totals in your area for the last year on BoM’s website.

Again, simply select your “Area” (state), and then “Rainfall Totals” for map. For period, you can select “1 month” and then click “Earlier” button to see the rainfall over each month of the previous year. Since weather changes from year to year, this will provide you with more accurate recent rainfall in your area.

Rain Differs Month-to-Month Per Season

It is important to note that rain doesn’t fall evenly throughout the year. So, on BoM’s website you should pay attention to how much rain falls during each month and season. Summer in Australia generally yields the most rain, since the heat evaporates more water which then condenses and causes precipitation to occur.

For most, this means most rain will fall December to February of the following year. Winter is generally the driest period. If you’re looking to harvest rain, it is therefore important to try have everything setup prior to the summer months.

Furthermore, rain doesn’t even fall evenly during a month. Rather, expect to have periods of no rain, and then most of the monthly rain to fall over a few days. This means, your rainwater tank may run dry during the year, but then when it rains, quickly fill with water. If you don’t have enough storage space, then it will overflow.

If you would find such disheartening, then you may want to invest in a larger tank or even several tanks to minimise rainwater wastage. An ideal solution is having your above ground storage for rainwater, and feeding the overflow into a second tank or an underground tank, and from there directing any excess water into the stormwater.