Groundwater comes from rain that trickles down into our aquifers. It gives us the lakes, wetlands, bushland and urban trees that make our City green. It's also under pressure due to climate change and increasing demand.
Perth's groundwater system remains vital to meeting our water needs, making up 40% of the largest scheme we manage, the Integrated Water Supply Scheme.
Groundwater is also used in local community parks and recreation areas, school grounds, local businesses and 1 in 4 household gardens through bores.
To secure our supply and protect our lakes and wetlands we are investing in a new expanded deep groundwater network. This will allow us to transfer our groundwater abstraction to less sensitive locations, including the deeper aquifers.
Changing our groundwater use
Over the past 10 years we've expanded our use of the deepest and most robust groundwater for supply to Perth.
- We've also accessed water from the coastal superficial aquifers that would have otherwise discharged into the ocean.
- Use of groundwater from the superficial inland aquifers has reduced, lessening impacts on some of our wetlands and lakes that are supported by the aquifer.
We now only rely on the superficial inland aquifers in the very driest of years and only for about 10% of our supply needs.
Expanding our groundwater network
We're investing in a secure, deep groundwater network so that by 2022, around half of Perth's drinking water will come from groundwater sources.
This means we'll be able to:
- Replenish the deep Leederville and Perth Yarragadee aquifers with recycled water through our new groundwater replenishment scheme.
- Draw water from the replenished deep aquifers.
- Develop new coastal superficial groundwater schemes to use water that currently flows naturally into the ocean at Eglinton and Yanchep.
- Continue to reduce our groundwater take from environmentally sensitive areas.
Aquifers are mostly composed of sand, sandstone and limestone, but they can also be made of gravel, heavily fractured granite, or any other rock material that has enough connected spaces to store and move water through it. It's from here that we take water from the ground and feed it into our water supply.
In Perth there are 3 layers of aquifers:
- Superficial aquifer - the shallowest aquifer which stretches across the coastal plain. Superficial aquifers are located closer to the surface and often express themselves as wetlands or lakes.
- Confined Leederville aquifer - below the superficial aquifer, and is separated by confining layers which minimises water movement. The Leederville aquifer is often several hundred metres thick, and in some areas it connects with the surface.
- Confined Yarragadee aquifer - the oldest aquifer that provides a robust supply even in dry years because of its vast storage and limited connection to the surface environment.