Assessing groundwater recovery scenarios for opencast mining using numerical modelling

Author: Caglar Bozan

Bozan, Caglar, 2021 Assessing groundwater recovery scenarios for opencast mining using numerical modelling, Flinders University, College of Science and Engineering

Terms of Use: This electronic version is (or will be) made publicly available by Flinders University in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. You may use this material for uses permitted under the Copyright Act 1968. If you are the owner of any included third party copyright material and/or you believe that any material has been made available without permission of the copyright owner please contact with the details.


A generic groundwater flow model is developed using the code MODFLOW (McDonald & Harbaugh 1988) in order to evaluate dewatering and groundwater recovery scenarios based on the Hope Downs-1 North mine site, Pilbara, Western Australia. Substantial lowering of the groundwater table is required for open-cut mine operations below the water table in the region to enable dry pit mining. If water management is not carried out carefully during dewatering activities, biodiversity, groundwater-dependent ecosystem, communities, wildlife in the region may become affected. With the cessation of mining, the water level around the dewatered mine pit will begin to rise. However, mine pits may become groundwater sinks, especially in areas such as the Pilbara, where the loss of water by evaporation is greater than the gain through rainfall. If recovery occurs, it may take several years until the groundwater reaches pre-mining groundwater levels, given the climatic conditions in the Pilbara. It is therefore critical for mine closure, to obtain reliable predictions of mine water recovery. This research examines 100-year groundwater recovery predictions through model scenarios based on a groundwater flow model, which mimics the overall geological and climatic conditions encountered in the Pilbara. Scenarios encompass the prediction of water level recoveries under different evapotranspiration and recharge regimes. Furthermore, backfilling of the pit and Managed Aquifer Recharge (MAR) are examined as two important water management strategies of mine sites. The backfilling scenarios prevented water loss in the pit lake due to evaporation. However, they were not able to speed up long-term water level recovery. Installation of 16 injection wells for MAR applications, saw roughly 29.5% of the water taken by dewatering returned to the pit. This resulted in a slightly faster recovery times, however, the impact remained minor.

Keywords: Groundwater recovery scenarios, Opencast Mining, Groundwater flow modelling

Subject: Hydrology thesis

Thesis type: Masters
Completed: 2021
School: College of Science and Engineering
Supervisor: Prof Peter Cook