Groundwater-dependent wetlands of the Broome Sandstone aquifer in the La Grange area, Western Australia

Page last updated: Wednesday, 17 January 2018 - 4:19pm

This page summarises a report that identified wetlands likely to be dependent on the Broome Sandstone aquifer within the La Grange groundwater allocation area. The Broome Sandstone aquifer is the dominant groundwater resource in the area.

With potential agricultural growth in this area, it is necessary to understand, monitor and manage the aquifer and its dependent wetlands to maintain ecological, cultural and other values for the Western Australian community.

Why we carried out this investigation

This investigation is part of a broader package of work on the capacity for new groundwater resources to be used to grow irrigated agriculture in Western Australia.

Using groundwater for irrigated agriculture could affect watertables that underlie wetlands in the La Grange area (Figure 1).

We carried out this investigation and production of a watertable model to identify groundwater-dependent wetlands that could be affected by irrigation. This information can then be used to plan for sustainable resource use and to avoid damaging off-site impacts from irrigation.

Map showing the La Grange project study area in the Pilbara region of Western Australia
Figure 1 Location of the La Grange project area and the groundwater allocation areas.

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What we did

We created a watertable-surface model to identify wetlands and determine which of the previously mapped wetlands are likely to use water from the Broome Sandstone aquifer.

We used 148 points taken from bore data to create the watertable-surface model. We then validated the accuracy of the modelled watertable surface with drilling data.

You can view results from the model through an interactive groundwater map.

What we found

The results of the drilling show a strong correlation with the modelled surface, which in turn was able to identify 43 groundwater-dependent wetlands (some of which were previously unmapped) (Figure 2) and validate 85 previously mapped wetlands (Yu 1999) as being groundwater-dependent.

A map of the La Grange area showing the distribution of identified wetlands.
Figure 2 Mapped distribution of 43 wetlands (marked with +) identified in this study.

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What this means

The watertable-surface app and map of wetlands provides multiple outcomes:

  • The multiple maps and web tools can assist irrigators and water managers to predict the depth to the watertable, saturated aquifer thickness and unsaturated areas within the La Grange groundwater area.
  • The watertable-surface app is an integral part of scenario modelling of the aquifer. Scenario modelling allows us to test a range of impacts on the aquifer and its wetlands from the further development of irrigated agriculture.
  • The wetlands mapped will assist stakeholders to identify and develop management plans to test and minimise environmental risks.

Acknowledgements

We carried out this investigation as part of the Regional Economic Development Water Opportunities Project, which aims to promote agribusiness through the development of land and water resources in the Kimberley. 

This investigation was made possible by Royalties for Regions investment by the Western Australian Government.

For more information

Download Resource management technical report 397, Identifying groundwater-dependent wetlands of the Broome Sandstone aquifer in the La Grange groundwater area, Western Australia.

Visit the La Grange Western Australia groundwater interactive map page.

Contact information

Nicholas Wright
+61 (0)8 9780 6286