The Gnangara groundwater system is Perth's largest source of low cost, good quality water. It supplies almost half of all the water used in the Perth metropolitan area each year (for drinking water, public open space irrigation, domestic garden watering and agriculture, among others). Perth’s lakes, wetlands and bushlands also depend on the Gnangara groundwater system. The Water Corporation uses about 40 per cent of the water abstracted from the Gnangara system to supply the Integrated Water Supply Scheme, servicing most households and businesses in the Perth and Peel regions.
The North Gnangara groundwater investigation aimed to improve our knowledge of the hydrogeology around the Yeal Nature Reserve, west of Gingin. We now better understand where and how the Superficial, Leederville and Yarragadee aquifers connect in this area. We also have a better indication of how pumping from deeper aquifers may impact Superficial aquifer levels and potentially affect groundwater-dependent ecosystems.
The North Gnangara groundwater investigation finished in 2009 in partnership with the Water Corporation. The project was part of our flagship State Groundwater Investigation Program and the Australian Government’s Water Smart Australia program.
What we did during the investigation
During this investigation we:
- constructed 65 monitoring bores in the Superficial, Leederville and Yarragadee aquifers
- installed automatic dataloggers in 49 bores, which record water levels at six-hourly intervals
- worked with Curtin University to improve our understanding of stratigraphy by completing more than 50 kilometres of seismic surveys.
- built a 3D conceptual model of the North Gnangara area.
Key findings and how we are using the information
The key findings from this investigation helped us to:
- delineate a hydraulic ‘window’ where there is a direct connection between the Yarragadee and Superficial aquifers – abstraction from the Yarragadee aquifer may impact Superficial aquifer groundwater levels in this ‘window’
- identify how the Yarragadee and Leederville connect in the Yeal area
- suggest that faulting was a more critical structural control than folding
- map where the Parmelia Formation separates the Leederville Formation into two distinct entities.
We have used the information to create a more accurate conceptual hydrogeological model and improve the Perth Regional Aquifer Modelling System (PRAMS). We have also used the data from this investigation to manage potential impacts to groundwater-dependent ecosystems in the Yeal area and manage deep aquifer abstraction and reinjection for public supply.
Where to get more details
You can ask for copies of the internal technical reports for this investigation by emailing groundwater.info@dwer.wa.gov.au. These include:
- North Gnangara bore completion report, HR277 (Pigois 2009)
- Conceptual geology of the north Gnangara Mound, HR288 (Pigois 2009).
Go to our Water Information Reporting portal to access data from the monitoring bores installed during the investigation.
You can access all government-commissioned airborne geophysical surveys via the Department of Mines, Industry Regulation and Safety website and download them free of charge from ‘Geophysical Surveys’ in GeoVIEW.WA or from the Geophysical Archive Data Delivery System (GADDS).
Read more about our groundwater investigations by region across Western Australia.
