Bulcock, HH & Heaslop, J 2019, 'The application of an agro-hydrological model for a data limited closure study of a bauxite mine in Australia', in AB Fourie & M Tibbett (eds), Mine Closure 2019: Proceedings of the 13th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1377-1390, https://doi.org/10.36487/ACG_rep/1915_108_Bulcock
(https://papers.acg.uwa.edu.au/p/1915_108_Bulcock/)
Abstract: Closure is a critical phase of a mining operation since this is when the environmental effects of mining and rehabilitation work, both biological and physical, are most stringently judged (Spain et al. 2015). This study considered the hydrological impacts of the final rehabilitated landform after closure relative to the pre-mine site. The bauxite mine is in Australia and hydrological data is limited. In order to compare the pre-mine condition to the final closure landform the Agricultural Catchments Research Unit (ACRU) agro-hydrological model was used as it can account for the changes in surface topography, soil profile and vegetation associated with mining. The assessment of the hydrological impacts included streamflow, baseflow, transpiration and peak discharge. Streamflow presents an integrated descriptor of the impact of the mining due to the removal of the bauxite layer from the soil profile and is affected by the quick flow and baseflow responses. Transpiration is an indicator of the vegetation water demands and provides insight into the species that should be used for rehabilitation. The peak discharge shows how the changes in the topography and land use will impact the functioning of the waterways post-closure. The aim of the final landform is to maintain the functioning of the waterways to as-close to the pre-mine conditions as possible. From the peak discharge output from the agro-hydrological model, the data was input into HEC-RAS 2D model to estimate the changes in flow velocity, shear stress, stream power and water surface elevation. The results from the study suggest that there is not a large change in flow volumes on an annual basis, but the peak discharge is reduced by up to 78% in some cases. The associated reduction in velocity, water surface elevation, shear stress and stream power are approximately 40%, 400 mm, 51% and 68% respectively. The findings from this study will provide context for potential remedial measure.

Keywords: agro-hydrological model, bauxite mine, closure, Australia