The demand for water in greater Geraldton for town supply, industrial and agricultural uses has grown, putting pressure on the region’s water resources. Further development of the Yarragadee aquifer, which provides scheme water for greater Geraldton, had been proposed as a potential source to meet future demand. To sustainably manage the resource, we needed to increase our understanding of where recharge enters the aquifer.
We investigated groundwater resources in the Allanooka and Casuarinas subareas between Dongara and Geraldton from 2007 to 2011. We improved our knowledge of the area’s hydrogeology through:
- developing a conceptual model
- improving recharge estimates for the Yarragadee aquifer
- expanding the groundwater monitoring bore network
We used the investigation’s findings and ongoing monitoring data to help develop the Arrowsmith groundwater allocation plan 2010, supporting the sustainable management of groundwater resources in the Mid West.
We completed the investigation in 2011 as part of our flagship State Groundwater Investigation Program.
What we did during the investigation
During the Allanooka–Casuarinas groundwater investigation we:
- collected both land and air-based geophysics data, including:
- an airborne electromagnetic (AEM) survey over an area of 2,325 square kilometres
- high-resolution shallow seismic surveys along two east–west transects totalling 58 line kilometres.
- completed an exploratory drilling program, installing 28 groundwater monitoring bores at 17 sites up to a maximum depth of 306 metres
- collected and analysed 33 groundwater samples for isotopes and hydrochemistry.
Key findings and how we are using the information
The investigation found that:
- there are broadly two groundwater flow systems – a local, shallow, fault-bounded freshwater flow system and a subregional, deep, brackish to saline flow system
- faulting significantly influences groundwater quality distribution – groundwater salinity contrasted significantly on either side of a major fault shown in AEM data
- groundwater is recharged seasonally even where the depth to water exceeds 100 metres, based on continuous datalogger monitoring of new and existing monitoring bores.
Our improved understanding of the Yarragadee aquifer’s hydrogeology and ongoing monitoring will help us develop future allocation plans and licensing in the Allanooka and Casuarinas subareas.
Where to get more details
You can download the Arrowsmith groundwater allocation plan 2010.
You can ask for copies of the internal technical reports for this investigation by emailing groundwater.info@dwer.wa.gov.au. These include:
- Bore completion report for the Allanooka–Casuarinas groundwater investigation, HR316 (Schafer et al. 2011)
- Allanooka–Casuarinas groundwater investigation, HR327 (Schafer 2016)
- Estimates of renewable fresh and brackish groundwater resources in the Allanooka and Casuarinas subareas, HR352.
- Groundwater monitoring review of the Yarragadee aquifer in the Allanooka-Casuarinas investigation area, HR367.
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.
