Integrating geochemical and hydro(geo)logical modelling to predict long-term water quality

Authors: Colston, RE; Ziukelis, L; Robinson, JDF; Balding, B Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2515_52

Cite As:
Colston, RE, Ziukelis, L, Robinson, JDF & Balding, B 2025, 'Integrating geochemical and hydro(geo)logical modelling to predict long-term water quality', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-15, https://doi.org/10.36487/ACG_repo/2515_52



Abstract:
SLR Consulting Limited is currently providing environmentalconsultancy services for a proposed hydropower scheme at the former Silvermines site in Ireland that will redevelop the closure setting: once more providing a resource from the area, which has a legacy of silver, baryte, copper, lead and zinc extraction through open-cast and underground methods. As part of this project, SLR is undertaking the prediction of water quality in the former Magcobar pit lake that will be used as a water source for the proposed hydroelectric power scheme. The modelling is designed to provide estimates of corrosion risk to the pump impellers and the risk to downstream water courses due to water discharge. A baseline study of the lake indicated that it was relatively well mixed, with varying concentrations of heavy metals/metalloids and other parameters typical of a pit lake which has been in existence for many years. The baseline study examined the dominant water sources and their respective chemistries entering the pit lake over time. In addition, changes in chemistry caused by the proposed civil works and circulation of water during the operation of the hydropower scheme have been assessed. To achieve this, the study has developed a pH-redox-equilibrium in C language (PHREEQC)-based modelling approach that accurately represents current geochemical processes underway in the pit lake and includes source terms such as groundwater, surface water and wall rock run-off to reproduce the measured pit lake water chemistry. This fed into a robust and innovative geochemical modelling using a combination of GoldSim and PHREEQC modelling software.

Keywords: pit lake, PHREEQC, GoldSim, modelling, hydropower, water quality

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