Influence of aquifer properties on optimal location and duration of groundwater level monitoring to predict aquifer recovery after mine closure

Open pit mines that extend below the water table are typically dewatered to create a dry mining environment. Knowledge of the extent and timing of water table recovery after mining is essential for managing long-term environmental impacts, planning site rehabilitation, and ensuring the sustainability of water resources. Predicting water table recovery requires knowledge of the geology and groundwater monitoring near the mine pit, where bores are concentrated. Usually, considerably less data is available further from the mine pit, yet this data is required to accurately estimate groundwater level recovery, particularly over decadal timescales. Estimating forecast uncertainty of groundwater level recovery and quantifying how groundwater level data collected at different distances from the mine affects this uncertainty can be challenging. To address these challenges, linear and data-worth analysis were employed to identify factors affecting uncertainty of groundwater level recovery and explore the value of near- and far-field data collection on short- and long-term recovery predictions across multiple forecasts. These analyses were conducted using synthetic groundwater models in FEFLOW representing an open pit mine in a sedimentary aquifer. Each scenario considered pre-mining, dewatering and post-closure conditions. The model results highlight how spatial variations in hydraulic conductivity, hydraulic controls and data availability contribute to reducing the uncertainty in groundwater level recovery predictions. The duration of data collected post-mining also influences the uncertainty predictions. The developed approach can improve the development of monitoring plans for mining industry, enabling resource-efficient data collection and informed decision-making prior to and during mine closure.