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Research to preserve Australia’s largest groundwater resource

Monitoring evaporation fluxes in areas of shallow groundwater tables fed by leakage from the GAB

Researchers at the Melbourne School of Engineering have been working with industry to better understand and monitor our most vital underground water reserve, the Great Artesian Basin.

Department of Infrastructure Engineering academics have measured the leakages from the basin in order to assist in the future sustainable use of this important water resource.

The project has been funded by the Australian Research Council’s Linkage program, along with mining sector industry partners, BHP-Billiton and Santos, and governance agencies, the Great Artesian Basin Coordinating Committee and South Australian Arid Lands Natural Resource Management Board.

The Great Artesian Basin (GAB) is the largest groundwater resource in Australia and one of the largest artesian basins in the world.

It lies beneath 22% of the Australian continent, covering much of the arid interior of central-eastern Australia. The majority of the natural flow from the GAB is through springs that are located in Queensland, South Australia and the Northern Territory.

These are intricately linked into Indigenous Dreamtime stories, as well as the exploration of the arid interior and early expansion of grazing enterprises. The sinking of bores into the GAB was crucial for supplying water to many of the iconic cattle stations of the interior and also to large mining operations.

However the fundamentals of the water balance in the GAB are still not well understood, in spite of its importance as a resource.

One of those components of the water balance is how much water leaks out of the aquifer. Some of this leakage could be going into overlying aquifers (usually salty) or into the near-surface and then evaporated. Identifying where and how much leakage is occurring will make a positive contribution to the sustainable management of the GAB’s water resource.

This project has tackled the ‘where’ and ‘how much’ question of this leakage component, concentrating on areas of high leakage around the margin of the GAB in South Australia.

Researchers embarked on four field trips into the arid north of South Australia to collect information on rates of evaporation around groundwater leakage areas.

Satellite data was also used to both identify the areas with identifiable groundwater leakage and also to extrapolate our field results over the 500 km length of the GAB margin in South Australia.
The project was successfully able to map the areas of highest leakage and found significant differences between regions fed by different groundwater flow paths.

Professor Andrew Western said that the field measurements of leakage from around the southwestern margin of the GAB support the Commonwealth Bureau of Rural Sciences earlier work identifying that leakage is important in South Australia, which was based solely on computer modelling.

“In fact, our measurements suggest that leakage rates in the western part of the GAB are higher than these earlier estimates. This raises a number of other questions about fundamental aspects of the water balance of the GAB.”

“For instance, are recharge rates across the western GAB higher than expected to balance this higher discharge or do these discharge rates reflect recharge rates from an earlier, wetter climate?”

The results will assist in improving modelling of groundwater movement in the GAB and in the sustainable allocation of this vital water resource. Research partner BHP-Billiton is using the results in the development of a new groundwater model for the region that will improve their management of groundwater resources.

“We believe that the results of this project will greatly assist in the sustainable management of the GAB resource and protection of its iconic springs, particularly in giving greater confidence in assessing the water balance in different regions of the GAB,” Professor Western said.

Further details about the project are available from the research projects database.

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