Salinity is a natural part of the Murray-Darling Basin (MDB) in South Australia, where the groundwater can be saltier than seawater. Natural flows of groundwater salt to the river can be impacted by changes in land use, river regulation, and engineering works. Numerical groundwater models provide quantitative estimates of groundwater salt entering the River Murray due to various management actions. This supports SA’s policy development and planning.
South Australia has developed, and is progressively refining, a suite of numerical groundwater MODFLOW models, for the River Murray in South Australia. The models represent decades of work by numerous groundwater modellers since the 1990s. The current models are typically updated and reviewed on a five-year rolling basis, ensuring that the models incorporate new data and knowledge. Improved modelling methodology, approaches and techniques have been applied over time. The models are developed collaboratively between policy officers and groundwater modellers to ensure assumptions and simplifications are appropriate, both scientifically and for policy purposes. A rigorous model review process is an important part of the model development where expert independent reviewers are involved at several stages.
Early generation groundwater models are usually limited by data availability and software capability. More advanced modelling techniques and software improvement enable current groundwater models to simulate closer to reality. A prototype model aims to allow real-time estimates of river salinity and to gauge the impact on floodplain ecology.
SA groundwater models successfully estimate salt load impact to the river from natural and anthropogenic processes. They also identify knowledge gaps in scientific understanding, and help to plan future research.