SALT SOURCES AND DEVELOPMENT OF THE REGOLITH SALT STORE IN THE UPPER BILLABONG

Australia has the largest ratio of salt-affected soils with respect to total surface area of any continent in the world. The processes of dryland salinity (which results from an increase in salts in solution) and consequent sodicity (where the soil complexes have high levels of adsorbed Na+, i.e. exchangeable sodium percentages ≥6) are major land and water degradation issues, particularly within the Murray-Darling Basin. In the catchments of southeast New South Wales such processes significantly impact on both agricultural production and water quality in the river systems. While the sources of salt found in the landscape have been debated by many workers, the general consensus is that the major contribution comes from precipitation, although attempts at direct comparison against other potential sources such as mineral weathering or aeolian dust are few in eastern Australia. This study assessed the contributions of various salt sources of the regolith in the Upper Billabong Creek Catchment (UBCC) of southeast New South Wales, and how these salts are stored and released in the environment. Such information is valuable in land and water resource decision-making, both within the catchment and in similar environments in neighbouring catchments, particularly with regards to prominent environmental issues such as soil sodicity, waterlogging and dryland salinity (Woodward-Clyde 1999, NLWRA 2001)