Author: Zlatko Eterovic
Eterovic, Zlatko, 2021 Improved calibration of a groundwater model using atmospheric tracers and particle tracking analysis, Pilbara WA, 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 copyright@flinders.edu.au with the details.
Elevated concentrations of chlorofluorocarbon (CFC)-12 have been measured from dewatering bores in the vicinity of a large open pit mine in the Pilbara, WA, indicating the presence of younger groundwater attributed to localised recharge processes from an adjacent creek. The calibration of a groundwater model with the assistance of atmospheric tracers has re-affirmed that creek recharge is contributing to the dewatering network within the surrounds of the mine. In this study, a pre-existing transient numerical groundwater model was calibrated using simulated equivalents of atmospheric CFC-12 concentrations via particle tracking methods. Particles were distributed uniformly along the screens/open intervals of the dewatering bores and simulated by reverse tracking back in time to areas of recharge. Particle tracking simulations were firstly undertaken on the pre-existing model and then calibrated by applying creek recharge to produce a closer match between simulated and measured CFC-12 concentrations. Both models were ultimately compared to assess calibration quality. Results from the simulations showed that applying a creek recharge rate equivalent to 0.009 m/d into the groundwater model improved calibration performance. Results proved to be spatially variable as some areas produced a closer match between simulated and measured concentrations over time in comparison to others. A sensitivity analysis was also undertaken using different rates of recharge to address sensitivities and uncertainty in recharge parameterisation. The root mean square error (RMSE) indicated that a recharge rate equivalent to 0.009 m/d (74 pg/kg) produced a closer match between simulated and measured concentrations in comparison to 0.006 m/d (81 pg/kg) or 0.012 m/d (76 pg/kg). However, all scenarios produced the same temporal trends indicating minor sensitivities in recharge were not enough to significantly alter results.
Keywords: Groundwater modelling, tracers, particle tracking, modflow, CFC-12, mining, mine dewatering, groundwater recharge, Pilbara
Subject: Hydrology thesis
Thesis type: Masters
Completed: 2021
School: College of Science and Engineering
Supervisor: Professor Peter Cook