Murray-Darling Basin Authority (MDBA)

A 3‐year study by the Murray-Darling Basin Authority and stakeholders has identified the broad scope of acid sulfate soils in the Basin.

This is the first time these potentially environmentally damaging soils and their associated hazards and risks have been identified on a Basin‐wide scale.

The MDBA worked with other Basin governments to train local stakeholders so that more than 19,000 wetlands received desktop assessment; 1,385 rapid on‐ground assessments occurred and nearly 200 wetlands and river reaches received detailed assessment ‐ including 14 of the 16 Ramsar‐listed wetlands in the Murray‐Darling Basin.
Waterways found to contain acid sulfate soils at levels of concern were located in the southern part of the Murray‐Darling Basin.

The project found that acid sulfate soils were extensive throughout many wetlands along the lower River Murray in South Australia and in the western part of the Edward‐Wakool River system in New South Wales. In Victoria, the affected sites were localised around Mildura and in some areas that were impacted by dryland salinity.

Due to recent flooding, acid sulfate soils are less of a concern, but the findings of this study will contribute to the ongoing management of acid sulfate soils. The study has achieved major advances in the understanding of acid sulfate soils in inland Australian aquatic ecosystems and has identified those areas with greater hazards and risks.

The development of acid sulfate soils occurs naturally, but changes to the hydrology of inland rivers and wetlands have contributed to the occurrence of these sediments in some areas.

If left undisturbed - and covered with water - sulfidic sediments pose little threat. However, when exposed to air, for example, with lower water levels under drought conditions, chemical reactions may lead to the generation of sulfuric acid, impacting on the health of a wetland.

Acid sulfate soils can release heavy metals and decrease oxygen in the water leading to the death of fish and other aquatic organisms.

State government and regional NRM agency involvement was key to the success of the study, especially for the rapid on‐ground assessment.