Development of water quality modelling of salinity in the Murray-Darling basin

Water quality modelling of salinity in the Murray Darling Basin has developed and is continuing to develop in response to information demands by the Basin?s stakeholders. The basin is a highly productive agricultural area with unique and valuable environmental attributes. Increasing salinity in the Murray was identified as a water quality problem over thirty years ago as high salinity levels result in costs across all sectors and affects the sustainability of aquatic ecosystems. A strategy put in place in 1987 to halt and reverse this water quality decline has recently been audited, and is being revised in response to results of recent investigations. Stage one of the audit questioned whether in stream salinity was rising as a result of dryland salinisation, and this was shown to be the case using simple stochastic modelling of in stream salinity data. This outcome prompted the more complex question of how much salinity was going to increase, and where and when these rises would be. Investigations were coordinated between the member states of the MDBC to model salt mobilisation and exports. Increases of 50-400% in salt loads were predicted over 20 100 years. Current investigations use GIS to refine estimates of the magnitude and distribution of the dryland salinistion, and will be used to update the basin salinity management strategy. The next phase of modelling will address questions on how to manage salinity with available resources. The modelling will need to assess the effect of management scenarios on the amount of land affected, reductions in salinity, and associated costs and benefits and environmental impacts. A suite of models including CATSALT and FLAG have been developed, and will be integrated to a river basin scale by routing the water and salt through IQQM. These hydrologic models will provide a basis for LAMPS a proposed environmental and socio-economic GIS based management planning system.