Before the Water for Pilbara Cities investigation, we were uncertain about groundwater recharge, perceived abstraction impact, aquifer characteristics, sustainable limits of abstraction and water quality in the West Canning Basin – Sandfire groundwater resource. These uncertainties resulted in risks to the sustainable management of the groundwater system and stifled investment from pastoralists and businesses.
By improving our understanding of fresh groundwater availability in the area, the Water for Pilbara Cities investigation has given greater certainty and confidence for regional development.
The investigation supported an increase in the groundwater allocation limit in the West Canning Basin – Sandfire resource from 30 GL/year to 50 GL/year. It also identified where further studies could help the long-term sustainable management of this resource.
What we did during the investigation
We conducted a program of drilling, airborne and downhole geophysics, water chemistry and isotope sampling, monitoring and aquifer testing to address some of the uncertainty and contribute to more robust groundwater management.
Through the study we:
- collected 24,000 square kilometres of aerial electromagnetic data
- constructed 29 bores at 15 sites
- conducted a 66-day pumping test of the artesian Wallal aquifer north-east of Port Hedland
- collected and analysed groundwater, surface water and rain samples for major ion chemistry and isotopes
- built a 3D digital geological model
- developed a numerical groundwater flow model.
Key findings and how we are using the information
Findings and outcomes from this investigation include:
- Large volumes of groundwater can be discharged quickly from the Wallal aquifer over an extended period and the water is fresh (typically 250 to 600 mg/L).
- We used the 3D numerical groundwater model to:
- estimate the availability of groundwater under different climate scenarios
- assess the cumulative impacts of abstraction on existing users
- quantify the potential for drawdown to affect groundwater outflow at Mandora Marsh mound springs and other groundwater-dependent ecosystems
- assess the potential of abstraction-induced seawater intrusion in the Canning–Wallal and Broome aquifers.
- Information from this investigation informed our revised allocation limits and water resource objectives – see the West Canning Basin allocation statement 2018.
- The monitoring network ensures we can evaluate the response of the groundwater resource to abstraction.
- We will assess the resource against the objectives established during this project, which will tell us whether the allocation limits are sustainable.
Where to get more details
You can ask for copies of the internal technical reports prepared for this investigation by emailing groundwater.info@dwer.wa.gov.au. These include:
- Bore completion report for the West Canning Basin – Sandfire groundwater investigation, HR374 (Department of Water 2017)
- Inversion and preliminary interpretation of airborne electromagnetic data from the West Canning Basin – Sandfire TEMPEST survey (Mira Geoscience 2016)
- West Canning Basin – Sandfire Project: hydrochemistry and isotope interpretation report, HR406 (DWER 2019)
- West Canning Basin groundwater model report (PSM 2017)
- West Canning Basin groundwater model – uncertainty analysis (PSM 2018)
Go to our Water Information Reporting portal to access data from the monitoring bores installed during the investigation.
You can read more about our groundwater investigations by region across Western Australia.
