Jones, D.R., Ellerbroek, D.A., and Townley, L.R. (1997), The hydrology and water quality of final mining voids, 22nd Annual Environmental Workshop, Minerals Council of Australia, Adelaide, 12-17 October, 208-224.

Predictions of the quantity and quality of water in voids are required for post-mining land use planning. Surface water bodies in final voids have a number of important differences from natural lakes that make it difficult to utilise existing computer models to predict long term water quality. These differences include a relatively lower surface area to volume ratio, closed drainage basins, and the potential for inflows from reactive materials that have been exposed or disturbed during the mining process. Lakes forming in final voids may be influenced by the hydraulic properties and weathering products of waste rock and tailings that form aquifers discharging into the system. These properties may change over time and the hydrology and water quality of the final void may evolve for many years before approaching a steady state. Development of post-mining land use plans for these features depends on the ability to predict water levels and water quality after they have filled with water and become final voids. The complexity and interdependency of hydrological and geochemical factors makes determination of water quality highly site specific. It is the aim of this paper to provide an overall summary of the key aspects which need to be addressed. Two case studies will be provided as examples to highlight how different combinations of hydrological and geochemical factors are of importance for different types of mining environments. The first case addresses the open cut strip mining of coal in the Bowen Basin (QLD), while the second case uses the Enterprise Pit at the Pine Creek Gold Mine (NT) as an example of a rapidly flooded open cut pit at a hard rock metal mine.