Title

Potential Impact of Geological Structures on Groundwater Flow Systems 

Alternate title

GW_FLOW_IMPACT_STRUCT 

Supplemental Information

Related Documents: None 

Status

Completed  

Code

4283 

Maintenance and update frequency

As needed  

Topic category

• Inland waters
• Geoscientific information

Use limitation

General 

Classification

Unclassified  

Statement

Dataset Source: The dataset comprises thirteen impact areas. Five areas have been assigned a type of Major for the following reasons: Otway Basin Lower Tertiary (Wangerrip Group) Aquifer - an area of known faulting in the Lower Tertiary which required the existing seismic mapping to be corrected/value added to better define aquifer thickness impact and because it is an area where ENE and N-S structures were cross cutting the basin; Gippsland Basin Latrobe Aquifer - an area of known faulting in the Lower Tertiary which had existing onshore/offshore seismic mapping that could be corrected/value added to define aquifer thickness impact and because the seismic mapping could show the continuity/connectivity of onshore aquifers and structure with areas of offshore fluid extraction that were known to be impacting onshore groundwater levels; North-west Murray Basin - earlier and recent studies indicated impacts of structure on groundwater flow, due to ample evidence in the geophysics of the NW and ENE structures, in addition to four key N-S faults and possible anomalous bedrock related to structure, and where impacts on groundwater could be identified in a part of the State which has the least bore coverage and where the groundwater systems are the least characterised in detail; Goulburn-Murray River Valleys - Nine Mile Creek area (Strathmerton) and Goulburn Valley (upper, middle and lower) were chosen because of good bore coverage which had previously been subjected to a lot of ground and regional geophysics coverage. This work indicated a complex bedrock (Permian and Palaeozoic) that appeared to be structurally controlled or controlling the Tertiary aquifer distribution and mixing of lesser quality groundwaters from the Goulburn aquifer system and the fresher ground water of the Murray system. Furthermore, there was evidence of anomalous bedrock and cross-cutting ENE-WSW structure which may enable a re-interpretation of the location of the ancient bedrock front with the Riverine plain and re-definition of the ancient Goulburn Valley; Ovens Valley - a fresh water bedrock valley system with recent groundwater assessment but it had not been studied using methodologies applied to other bedrock valley systems further west and had limited geophysics input to groundwater assessment. Furthermore, there was evidence of cross cutting ENE-WSW structures and anomalous bedrock depth indications. The remaining eight Areas assigned Other have been identified for the following broad reasons: Differences in the bores-only contoured bedrock depth map and a bore-controlled residual gravity map at various locations across the state (which may have some basis in reality or is partly or wholly an artefact of limited borehole control and intra-bedrock gravity anomalies; The local interaction of topography, magnetic, radiometric and to a lesser extent, gravity lineaments and apparent depo-centres; The coincidence of locally fresher groundwaters, structures and scoria cones in the Western Volcanics plains (in the case of the Ballarat impact area). The Streatham area which is part of the Wannon River catchment area has been examined in a little more detail. Dataset Originality: Derived 

Classification

Unclassified  

Attribute Quality

Comments

Not known 

Positional Accuracy

Comments

Not known 

Conceptual Consistency

Comments

Not known 

Missing Data

Comments

Victoria 

Excess Data