Smith, A.J., Dionne, I., Gresswell, R.A., Townley, L.R., Toogood, G.M., Neame, T., and Narayan, K.A. (2015), Challenges for water sharing in the context of large-scale and long-term impacts on regional groundwater systems, Australian Groundwater Conference, Canberra, December.

A key objective of water policy is to achieve equitable sharing of water resources between competing uses – both now and in the future. Predictive groundwater flow modelling currently provides the only means by which potential implications of current water management practices can be forecast and the effectiveness of management options assessed. The NSW Aquifer Interference Policy is an example of recent water policy that requires the impact of water taken from a water source to be predicted prior to approval, including the direct take from the target water source and indirect take from connected groundwater and surface water sources. Recent regional-scale groundwater modelling of the potential impacts of proposed coal seam gas development in the Gunnedah Basin has shown long response times to depressurisation within the basin, and very slow movement of groundwater between connected water sources. Potential transfers of water from shallow unconfined aquifers to deeper aquifers are predicted to occur hundreds of years after coal seam gas development has finished; the rates of transfer are very small but sustained over long periods. Within the context of existing water policy, it is challenging for regulators to decide how a potential indirect interference to an aquifer, many years in the future, should be considered by regulators and other stakeholders. The presentation will include methods for presenting and visualising modelling results to assist in meeting this challenge.