Acid sulfate soil toposequences in wetlands of the Lower River Murray

Abstract

Water levels have fallen dramatically in wetlands along a 250 kilometre length of the lower River Murray between Blanchetown (Lock 1) and Wellington, South Australia, in many cases exposing acid sulfate soil materials. The objective of this study was to provide critical baseline information to support management decisions for the soils and wetlands to minimise impact of these inland region acid sulfate soils. This paper: 1) presents an overview of the acid sulfate soil characteristics, 2) demonstrates the utility of toposequence models to provide an understanding of soil variation, and 3) describes how the information is used to support planning of management options. For 62 wetlands, a total of 198 sites were investigated. Acid base accounting data identified 534 out of 653 samples (82%) as having a positive net acidity. Classification of soil material based on pH and chromium reducible sulfur values identified acid sulfate soil material in 270 out of 638 samples (43%). Forty-seven of the sixty-two wetlands (71%) have an acid sulfate soil extent within the wetland that is of concern. Conceptual toposequence models were developed which identified a recurring pattern of soil variation and provided a useful means to communicate information to decision makers and managers.