River Murray Floodplain Groundwater Model 2015: Salinity dynamics of the River Murray floodplain in South Australia

Groundwater models produced from GOYDER INSTITUTE FOR WATER RESEARCH Project No. E1.11.

A series of numerical groundwater models have been designed to represent generic floodplain conditions that exist along the River Murray in SA, from the border to Lock 1. The aim is to improve understanding and modelling capability of flow and salinity dynamics, to assist with management and engineering decisions.

Multiple base case scenarios are considered, varying by floodplain topography, the presence or local absence of a lock, and whether the river conditions are gaining, throughflow or losing. Model variants were developed to investigate how results depended on the methods used to simulate key processes, including river level changes, floodplain inundation, groundwater evapotranspiration, and solute transport.

The MODFLOW and MT3DMS simulations were developed using Groundwater Vistas version 6. Some data inputs were pre-processed using scripts in Python 2.7.6.0. Post-processing was done with both Groundwater Vistas and Python.

Model parameters are informed by an amalgamation of data from the study area, but are not specific to any one location. Where there is a wide range of possible parameters, values from the Pike Floodplain have been adopted. Where no local field data exists, values were used from the literature and/or from DEWNR’s Salinity Register regional models.

As the Goyder Floodplain Model is a synthetic model, in that it does not model a specific location, no detailed calibration was possible. However, the models were constrained based on the current knowledge of floodplains along the SA River Murray, such as in-stream geophysics, estimated actual evapotranspiration, and Run of River estimates of groundwater salt flux to the river.


Location:
- South Australia, Australia
- The models simulate a generic domain representing conditions in the River Murray floodplain between the SA Border and Lock 1. Conditions are similar upstream of the SA Border as far as Nangiloc-Colignan.