Model-based Investigations of Acidity Sources and Sinks of a Pit Lake in Western Australia

Lake Kepwari is a rehabilitated lake in the Collie Basin lignite mining area in Western Australia. The water quality of Lake Kepwari was modeled with the pit lake hydrodynamic and water quality model PITLAKQ. Based on a hydrodynamically validated model, water quality scenarios were used to quantify the sensitivity of different acidity sources including groundwater exchange, surface runoff and erosion, providing new insights into the system. The technique of monthly aggregation of all sources and sinks of acidity, based on detailed model output, provided the basis for useful conclusions. Model results suggest a new focus of field investigations to improve modeling certainty and a follow-up, improved phase of modeling.