Katarapko Freshwater Injection

WGA AU | Wallbridge Gilbert Aztec - Photo: Katarapko Freshwater Injection

The Project

The Katarapko Freshwater Injection Project included the construction of a blocking bank on the Katarapko Floodplain to enable periodic inundation to enhance infiltration and promote a reserve of freshwater in the underlying shallow saline groundwater system to support vegetation is being constructed. Two issues were identified; the infiltrated fresh water would displace some of the shallow saline groundwater, and vegetation between the blocking bank and river would not benefit from the periodic inundation that would occur behind the blocking bank.

Injection of freshwater into the shallow saline groundwater system was trialled as a management option to mitigate the risk of displacing existing freshwater lenses. 

Technical Solutions

WGA was engaged to undertake a freshwater injection trial to gauge the potential for managed aquifer recharge (MAR) to mitigate the impacts on the vegetation between the blocking bank and river from saline groundwater displaced by inundation behind the blocking bank.

The trial demonstrated that a properly installed and operated MAR system could successfully develop and maintain a fresh groundwater lens. Over 114 days of operation, at an average rate of 1 litre per second, 2,500 kilolitres of water sourced from Katarapko Creek was recharged into the aquifer resulting in the development of a freshwater lens with a salinity of less than 5,000 micro siemens per centimetre (µS/cm) approximately 6 m thick and 40 m in diameter. This proof-of-concept trial demonstrated that the MAR system does not need to be complex, the infrastructure can have a small footprint, and the freshwater lens can be established with relatively small volumes of water. Once established, the freshwater lens can be maintained without significant decay at salinities less than 5,000 µS/cm for more than two months.

Client Focus

The success of this trial lay in the initial characterisation of the source water and the target aquifer, low injection rates and the adoption of a stepwise approach to testing various combinations of pre-treatment options and supporting infrastructure. Rather than installing a large and costly pre-treatment system, a bespoke system was designed to be consistent with the secondary trial objectives, such as; ensuring that any future scheme could be reliably installed and operated in an environmentally sensitive and remote area with limited infrastructure, minimal operator intervention and small footprint. Vegetation response monitoring, soil salinity monitoring and surface geophysics were carried out in parallel with the injection trial to validate the trial outcomes independently.

The Katarapko Freshwater Injection is included in the following sectors & services.
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