Developing causal pathways

The approach taken in the Maranoa-Balonne-Condamine subregion has leveraged existing state-based resources and knowledge of geological, surface water and groundwater conceptual models. The geological and groundwater conceptual models are consistent with the Office of Groundwater Impact Assessment (OGIA) regional groundwater model, which is ‘a regional groundwater flow model for making predictions of groundwater impacts from the petroleum and gas activities and for developing the … Spring Impact Management Strategy’ (QWC, 2012). The groundwater numerical modelling approach undertaken in the Maranoa-Balonne-Condamine subregion is detailed in companion product 2.6.2 (groundwater numerical modelling) (Janardhanan et al., 2016). The OGIA model is re-run annually based on the latest available industry development plans. As such, it has the best available representation of operational and planned CSG development in the subregion for cumulative groundwater impact assessment.

The OGIA model was revised for the BA to also simulate water-related impacts of coal mine development in the Maranoa-Balonne-Condamine subregion. However, the OGIA model may not on its own be suitable for assessing impacts on groundwater-dependent ecosystems or surface water – groundwater interactions. Licensed surface water and groundwater entitlement volumes are available. However, volumetric measurements of surface water or groundwater use and identification of the source of groundwater were identified as knowledge gaps in companion product 1.5 for the Maranoa-Balonne-Condamine subregion (Cassel et al., 2015). This report also identified that long-term, consistent water quality data measurements of surface water and groundwater systems in the Maranoa-Balonne-Condamine subregion were not available. For these reasons, the Assessment team has not developed a coupled surface water and groundwater numerical model of the Maranoa-Balonne-Condamine subregion.

The implications of this approach are that several companion products are not required for the BA in the Maranoa-Balonne-Condamine subregion, as described below. Companion product 2.1-2.2 (observations analysis, statistical analysis and interpolation) is not required because the Assessment team did not develop a surface water numerical model and the observations analysis, statistical analysis and interpolation in the development of the OGIA model is well documented (GHD, 2012; QWC, 2012). Companion product 2.5 (water balance assessment) is not produced. Instead the water balance and analysis of the surface water – groundwater interactions are documented in companion product 2.6.2 for the Maranoa-Balonne-Condamine subregion (Janardhanan et al., 2016). Product 2.7 (receptor impact modelling) is not produced because the Assessment team cannot use surface water numerical modelling to estimate hydrological changes or quantify all hydrological response variables necessary for this product.

The ‘Conceptual modelling of causal pathways’ workshop was held in Brisbane in July 2015. The key system components, processes and interactions for the geology, hydrogeology and surface water of the subregion were summarised and potential causal pathways were discussed with stakeholders at this workshop. The Assessment team refined the landscape classification of the main biophysical and human ecosystems that captures the high-level conceptualisation of the subregion at the surface through consultation with stakeholders at the workshop and separate meetings with experts from the Queensland Government. Discussion of the potential causal pathways considered the coal resource developments included in the groundwater modelling, hazards, impact causes, impact modes, activities and the resulting water-related effects identified by the IMEA. Discussion with stakeholders focused on knowledge gaps and uncertainties identified by the Assessment team.

Last updated:
16 October 2018
Thumbnail of the Maranoa-Baloone-Condamine subregion

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