Yarragadee Aquifer facts for kids

The Yarragadee Aquifer is a very important underground water storage area, like a huge natural sponge, found deep below the ground in the southwest part of Western Australia. Most of it is under a flat area called the Swan Coastal Plain, which is west of the Darling Scarp. This aquifer stretches a long way from Geraldton in the north down to the south coast. Near Perth, the aquifer splits into two parts. The southern part is known as the South West Yarragadee Aquifer.

This underground water source is quite deep, often hundreds of metres below the surface. It can be as thick as two kilometres in some places!

In the Perth area, the Yarragadee Aquifer sits below another aquifer called the Leederville Aquifer. The Leederville Aquifer itself is below two shallower water sources known as the Gnangara Mound and Jandakot Mound. These different water layers are separated by special layers of rock or clay called aquitards, which stop water from easily passing through them.

How Much Water Does It Hold?

The Yarragadee Aquifer holds an amazing amount of water – about 1,000 cubic kilometres! To give you an idea, that's like 1,000 billion litres of water. For comparison, the Gnangara Mound, which is much shallower, only holds about 20 cubic kilometres. Because it holds so much water, the Yarragadee Aquifer is a really important source of drinking water. The Water Corporation in Western Australia currently takes out about 45 gigalitres (45 billion litres) of water from it each year.

Where Does the Water Come From?

The Yarragadee Aquifer gets its water from rainfall. This process is called "recharging." It usually happens in areas where parts of the aquifer are closer to the surface, sometimes near other aquifers like the Leederville Aquifer. There are also places where the aquifer comes close to the surface near the Blackwood River. Experts believe that about 280 to 340 gigalitres of water flow into the aquifer each year from rainfall. The water in this aquifer can stay there for a very long time. In some parts, the water is more than 30,000 years old!

What Is the Aquifer Made Of?

Geologists, who study rocks and the Earth, call the rock layers that make up this aquifer the Yarragadee Formation. This formation is a very thick layer of rock found in the Perth Basin. It was formed a very long time ago, during the Jurassic Period, which was when dinosaurs roamed the Earth!

The Yarragadee Formation is mostly made of a type of sandstone. This sandstone is quite porous, meaning it has tiny holes, and it's not very strongly cemented together. This allows it to hold a lot of water, making it a great place for groundwater to collect. The bottom part of the formation has more shale and siltstone, while the upper parts are cleaner sandstone.

Interesting Facts

The famous Dalkeith Hot Pool was created by warm water that came from the Yarragadee Aquifer.