Assessing the performance of ground-coupled heat exchangers (GCHE) of closed-loop geothermal systems installed in tailings ponds is studied. A heat transfer model is constructed, taking into account heat conduction as well as groundwater advection. A three-dimensional finite volume discretisation method over a structured mesh with variable grid size is used to solve the governing equations. The performance of a GCHE system installed in tailings ponds is assessed based on the rate of energy extraction and the outlet fluid temperature. The geothermal capacity of mine tailings ponds and its sustainable rate of heat extraction are estimated. Effects of tube network configuration and horizontal and vertical underground advection on the performance of the system are investigated. It is found that two-dimensional heat transfer models may lead to over-designed systems and the effect of advection cannot be neglected in highly pervious tailings.