The Ramsar Convention's resources on Wetland Restoration

The STRP Expert Working Group on Wetland Restoration

Restoration Approach: Maintenance of water cover to prevent sulfuric acid run-off in acid sulfate soils

Wetland Type: Estuarine wetlands at elevations less than 5 metres above sea level with iron sulfide soil layers, mostly along northern and eastern Australian coasts

Background: Under normal conditions, acid sulfate soils are covered with water and vegetation, which prevents oxygen reacting with the iron sulfides. However, drainage and excavation of these areas exposes the iron sulfides to air, increasing the natural rate of oxidation and producing sulfuric acid. When coastal wetlands are drained, they can constantly release sulfuric acid and aluminium. Heavy rains can wash large slugs of sulfuric acid into surface waters like creeks and wetlands, resulting in massive fish and plant kills. Less obvious effects are reduced hatching and decline in growth rates and smothering of habitat.

Maintaining water cover is a simple solution where this is practical. Covering affected land with water, such as re-establishment of wetlands, encourages growth of acid tolerant water grasses, and provides drought pasture for stock, although the water must not be re-drained. Changes in operation of existing flood gates can allow reinstatement of former water regimes to reduce the impacts of acid sulfate soils and restore estuarine functions to tributary creeks.

Advantages: Uses natural processes to restore water regime and water chemistry; quick local response in wetland health is visible to community and funding bodies.

Disadvantages: Limited to wetlands able to be controlled by existing floodgates or the installation of small control structures; need ongoing management and monitoring for most effective results; some evidence suggests that reflooding will not reverse oxidation of iron sulfides under all circumstances.

Further information:

Wetland Care Australia web site www.wetlandcare.com.au  for fact sheet on Acid Sulfate Soils
Rebecca Lines-Kelly, NSW Agriculture on rebecca.lines-kelly@agric.nsw.gov.au

Rehabilitation References

White, I., M.D. Melville, B.P. Wilson, and J. Sammut. 1997. Reducing acidic discharges from coastal wetlands in eastern Australia. Wetlands Ecology and Management 5: 55-72.

-- Contributed by Stephen Hunter and Anne Jensen

Return to STRP Wetland Restoration index page

For further information about the Ramsar Convention on Wetlands, please contact the Ramsar Convention Bureau, Rue Mauverney 28, CH-1196 Gland, Switzerland (tel +41 22 999 0170, fax +41 22 999 0169, e-mail ). Posted 8 January 2001, updated 15 February 2002, Bill Streever and Dwight Peck.