Acid sulfate soils

Acid sulfate soils occur naturally in coastal and fresh water areas, and are found in wetlands and floodplains along the River Murray.

Whilst covered by water, acid sulfate soils are a harmless, normal part of the environment. But if water levels drop and the soils are exposed to air they can react with oxygen to form sulfuric acid (the same acid as in a car battery) and release metals such as manganese and aluminium.

When the exposed soils are rewetted, by rainfall or increased river flow, the acid and metals can be transported and negatively affect large areas.

Natural cycles of drying and flooding once flushed from the river system the small amounts of acid that occasionally formed. Controlling the River Murray's flow with structures such as weirs and locks, however, has resulted in less natural cycles and so a build-up of acid sulfate soils in some areas.

Coorong and Lower Lakes

One area that has suffered from acid sulfate soils build-up is the Coorong and lakes Alexandrina and Albert (the Lower Lakes) area. When water levels in the lakes reached unprecedented lows (-1.0 m Australian Height Datum (AHD) in Lake Alexandrina) during the drought of 2006-2010, large areas of acid sulfate soils were exposed. More than 20,000 hectares of acid sulfate soils became exposed. The consequences to local communities included decreased water quality, health issues for people and livestock, dust storms, sulfuric odours, ecological degradation and fish kills.

The main way to prevent acidification is to ensure that built-up acid sulfate soils are kept wet and not exposed to air for long periods. Acid sulfate soils can be managed in the Lower Lakes by taking action to maintain water levels between 0.4 m and 0.8 m AHD.

Research and monitoring

Extensive research and monitoring is under way to help fill knowledge gaps and inform management decisions.

See the monitoring reports.