Hydrostratigraphic model of the Gambier Basin and South West Murray Basin

A three-dimensional hydrostratigraphic model of the entire regional groundwater flow system that includes the Gambier Basin and the south western Murray Basin has been produced. The domain of this model stretches from the Dundas Plateau in Victoria to the Padthaway Ridge in South Australia and includes the Lower Limestone Coast and Padthaway Prescribed Wells Areas in South Australia, as well as part of the Border Designated Area (Zones 1A/1B to 6A/B and part of Zones 7A/B). The domain of the hydrostratigraphic model was governed by the boundaries of the South East Regional Water Balance Model, which is being developed as part of a Goyder Institute for Water Research project. This groundwater flow model required a hydrostratigraphic model that covered the whole regional groundwater flow system that encompasses the Lower Limestone Coast Prescribed Wells Area. This is the first cross-border hydrostratigraphic model to be produced for this region. The hydrostratigraphic model includes five layers,

Layer 1: the Quaternary Limestone Aquifer,

Layer 2: the Upper Mid-Tertiary Aquifer (Gambier / Murray Group Limestone Aquifer),

Layer 3: the Upper Tertiary Aquitard,

Layer 4: The Lower Tertiary Aquifer (Mepunga Formation) and the Lower Tertiary Confined Aquifer (Dilwyn Sand / Renmark Group Aquifer) and

Layer 5: the Pre-Cainozoic Sediments and Basement (however, the model does not include data for the base of Layer 5).

The model includes the following datasets:

Topographic Surface:

• SA/VIC State 1 second Digital Elevation Model (DEM), later updated with a version that includes lidar DEM data where available.

Top of Layer 2 (Top of Gambier / Murray Group Limestone):

• 2,697 stratigraphic data points for the South Australian portion of the model domain.

• 209 stratigraphic data points for the Victorian portion of the model domain.

Top of Layer 3 (Top of Aquitard):

• 733 data points for the whole model domain, including Victoria.

Top of Layer 4 (Top of Dilwyn Sand / Renmark Group) – Layer 4 includes the Pember Mudstone and Pebble Point Formation.

• 874 stratigraphic data points for the South Australian portion of the model domain.

• 83 stratigraphic data points for the Victorian portion of the model domain.

Top of Layer 5 (Top of Basement):

• 243 points for the South Australian portion of the study area. These were restricted to the Murray Basin (northern) portion of the study area.

• Contours of basement outcrops in the northern part of the SA portion of the study area.

• Contours derived from petroleum well and seismic data for the southern portion of the South Australian part of the study area.

• 63 points on the Victorian portion of the study area. The hydrostratigraphic model was created in an ArcGIS framework and is available as an ArcGIS geodatabase.

The parent datasets described above are also available in ArcGIS format. This study was supported by The Goyder Institute for Water Research