Kimmo Hentinen (GTK), Geological Survey of Finland, PO Box 1237, 70211 Kuopio, Finland. kimmo.hentinen(at)gtk.fi
In water management, modelling is a tool for studying and predicting water resources and their behaviour. In the mine closure process, modelling is often used to predict the changes caused by the termination of mining activities. Mining impacts on water resources are commonly modelled throughout the duration of mine operations as well. In this scenario post closure modelling can easily be conducted, as much of the required data is already available. Modelling can only provide a representation of reality as accurate as the data inputs, and it is the modeller’s responsibility to evaluate the accuracy of the model.
In water balance modelling the amount, relationships and changes in water resources are evaluated. This is usually done during mining to support decision making related to operations. After mine closure, the evolution of a mine’s water balance can be predicted decades into the future. Groundwater flow modelling can also be made during the closure process as a part of water balance modelling. Both underground and open pit mines, which typically extend below the pre-mining water table, can impact groundwater levels in the area surrounding the pit/underground galleries. The water table has to be controlled based on mining operation requirements, which often means lowering the water table around the mine. After mining, groundwater levels are not controlled, which leads to rebound of the water levels and flooding of the underground mines and open pits. Changes in water table levels and flow patterns can be predicted to evaluate effects on, for example, supply wells.
Possible contaminants in groundwater can also be studied using transport modelling. Through an understanding of the groundwater flow systems, it is also possible to evaluate the transportation and concentrations of contaminants of concern. As the groundwater flow is usually slow, transport of contaminants can be predicted for decades into the future. Transport modelling can act as a support tool for monitoring needs.
The following modelling technologies were evaluated in Closedure: