The SA River Murray and its floodplain are naturally prone to salinity, and this propensity has increased over the past century due to the construction of river locks and the introduction of large-scale land clearance and irrigation. To manage river and floodplain salinity effectively, SA must understand the short-term movement of water and salt within the floodplain landscape, under present conditions and under various management options for delivering environmental water. To address this issue, the project had the following objectives:
1. To prioritise river reaches and floodplain processes, by consolidating prior studies and existing datasets in a literature review and salinity risk framework.
2. To determine how DEWNR can simulate key floodplain processes in-house. This includes assessments of the impact on simulation accuracy of different assumptions/simplifications and data limitations.
3. To design MODFLOW and Source pilot models.
4. To develop a works program to prioritise improvements in the modelling required and inform targeted data collation and scientific studies.
The project objectives were met via the following tasks. A detailed data and literature review was conducted. A conceptual model of floodplain processes and drivers was developed, and presented to stakeholders and other experts for review at a workshop. Past risk assessments were reviewed and recommendations were made on how to populate a comprehensive risk framework. MODFLOW models of groundwater flow and solute transport were used to test approaches for simulating river level change, evapotranspiration, and flooding. A Source model was modified to simulate the impact of wetlands recharging the watertable on salt movement to the river, with a variety of conceptual models tested using Fortran. Recommendations for further work address site monitoring, how to reduce conceptual gaps, and additional modelling studies.
The project was designed so that DEWNR and other stakeholders could readily act on project results and many of the project outcomes and recommendations are already incorporated into related and/or follow-up projects.
The SA Riverland Floodplain Integrated Infrastructure Project (SARFIIP):
DEWNR policy, groundwater and surface water staff involved with the Basin Salinity Management Strategy (BSMS) are using project recommendations to:
DEWNR commissioned Flinders staff from the project to develop a tool for calculating groundwater salt flux to the SA River Murray floodplain for existing DEWNR groundwater models. The tool was written in Python, and DEWNR staff were trained to use and modify the code.
Several members of the Goyder project team are continuing River Murray floodplain salinity work in the ARC Linkage project, Dynamics of riverine freshwater lenses, a joint project between Flinders University, Monash University, and DEWNR. This aims to improve understanding and management of sites likely to include Nyah-Colignan, Chowilla, Pike, and Katarapko-Bookpurnong.