The Murray-Darling Basin Authority (MDBA) has concluded a three-year investigative study into levels of acid sulfate soils in the Basin, finding extensive levels of the potentially damaging soils in the southern part of the Murray-Darling Basin.


The study is the first time the 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.


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.


While the MDBA found that recent flooding had mitigated much of the problems associated with acid sulfate soils, the Authority conceded that it was an ongoing problem that would have to be addressed in the future.


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.