Gingin Brook is a unique freshwater perennial brook north of Perth with historic, cultural and environmental values. There has been widespread growth along the brook for horticulture, cattle grazing, market gardens, large orchards, fertilised pasture for grazing and semi-rural residential development. Development is restricted mainly to within one to two kilometres of the brook, with water either pumped directly from the brook or production bores in adjacent aquifers.
Abstraction, channel modification and the drying climate have significantly modified the brook’s hydrology, and now there is no summer flow in some sections of the brook. In the lower reaches, where the brook meanders across the Swan coastal plain, the relationship between baseflow in the brook, groundwater discharge, and surface/groundwater connection was unclear.
We investigated groundwater connectivity to the brook from 2007 to 2009 as part of our flagship State Groundwater Investigation Program.
This project significantly improved our understanding of how the brook interacts with the groundwater system. The new groundwater monitoring network provides data to help us evaluate and manage the system over time.
What we did during the investigation
Through the Gingin Brook investigation we:
- installed 32 monitoring bores at 16 sites along Gingin Brook and its tributaries – Moondah and Mungala brooks
- collected samples to analyse palynology (pollen grains and other spores) to determine the geological formations present
- analysed chemistry of groundwater samples
- installed dataloggers in bores, which measure groundwater levels every six hours
- collected surface water levels and flows at two gauging stations and undertook spot gauging of streamflow between February 2007 and September 2009.
Key findings and how we are using the information
The investigation found that:
- Groundwater discharge provides baseflow to the brook in two main areas – downstream of the confluence with Mungala Brook and in the upper catchment north-east of Gingin townsite.
- There is evidence of groundwater discharge to the brook from the deeper Leederville aquifer.
- There is a high level of connection between the brook and groundwater in some areas.
We used the findings from this investigation to help develop strategies to improve flow conditions in the brook. These include limiting summer surface water abstraction and implementing a buffer zone around the brook to limit groundwater abstraction impacts.
We used the findings and recommendations to inform the Gingin surface water allocation plan 2011 and the Gingin groundwater allocation plan 2015. We continue to collect monitoring data to evaluate the groundwater resource.
Where to get more details
You can download the following:
- a summary of the investigation’s findings
- Gingin surface water allocation plan 2011
- Gingin groundwater allocation plan 2015.
You can ask for copies of the internal technical reports for this investigation by emailing groundwater.info@dwer.wa.gov.au. These include:
- Pre-investigation review of the Gingin Brook project, HR258 (Lindsay et al. 2007)
- Gingin Brook bore completion report, HR275 (Tuffs 2009)
- Groundwater-surface water interaction along Gingin Brook, Western Australia, HR286 (Tuffs 2010)
- Northern Perth Basin Bulletin.
Go to our to access data from the monitoring bores installed during the investigation.
Read more about our groundwater investigations by region across Western Australia.
