Coal mining can affect groundwater levels, which can in turn affect organisms, ecosystems, and other groundwater-dependent assets such as waterholes or irrigation wellbores. This project is part of a larger body of work undertaken by CSIRO, BoM, Geosciences Australia, and Government departments, to quantify the effect of proposed future coal mining on large regions within Australia. This project studies the Hunter valley region. A regional-scale groundwater model containing past, current and future mines will be built. It is important to run this model many times in order to quantify how uncertainties in the model inputs, such as rainfall rates, or aquifer properties, translate to variations in model results. In this way the final results will be a probability distribution that will provide the public and policy-makers better insight into the modelling results. Using the supercomputer will make this possible.