United Wambo: groundwater impact assessment

Predictions supported by uncertainty analysis

The groundwater impact assessment involved review of historic data and field studies in order to gain an in-depth understanding of the hydrogeological regime for development of the conceptual groundwater model. The project is located in an area with rich coal resources and a long mining history on surrounding lands. Representing the cumulative impacts from previous mining and surrounding mines posed a significant challenge for the project. We undertook an extensive data review process, consolidating disparate data sources in one database. We used this to develop the conceptual model and an extensive numerical model across an area of 640 km2. The model also represented geological detail, its 34 layers, being the most detailed regional model developed within the Hunter Valley to date.

This detail allowed the many complex mine plans for open-cut and underground operations within the Whittingham Coal Measures to be represented within the model. This complexity in the model was possible with the use of MODFLOW-USG model code that allowed flexibility in the model layers and mesh structure. The magnitude of the predictions were supported through uncertainty analysis to assist the decision making process.