Oral Presentation Australian Freshwater Sciences Society Conference 2018

Catchment salt balance and historical salinity flushing quantified in a high rainfall stream (Mount Lofty Ranges, South Australia)   (#82)

Thomas A Anderson 1 , Erick A Bestland 1 , Ilka Wallis 1 , Huade D Guan 1
  1. Flinders University, Bedford Park, SA, Australia

Human-induced landscape salinization, including dryland salinity, has had devastating consequences on many catchments in southern Australia. Salinization occurs due to increased recharge and a rise in groundwater tables following land clearing of deep rooted native vegetation. In low lying areas with poor drainage groundwater table rise can lead to evapotranspiration and salt scalding. However, these same processes of increase recharge and groundwater table rise can lead to decreases in salinization as the historic salts are flushed into surface waters. This study in the Mount Lofty Ranges of South Australia documents a case of catchment desalinization. In the Scott Creek catchment, a 28 year record (1989-2016) of flow and salinity data were analysed on a monthly basis. Analysis of catchment-scale chloride deposition and export determined that approximately three times more chloride is being exported than is being received by catchment from atmospheric sources. Salt load exported to surface waters over the time period analysed was calculated to decrease on average by 6.4 tonnes per year, due to freshening of the catchment. Furthermore, analysis of an intermittent sub-catchment demonstrates accumulation of chloride rather than export during dry years whereas in the permanent stream catchment chloride accumulation is rarely greater than export. Findings from this study show that a continuous, high resolution monitoring history is required to thoroughly evaluate salt input and export.