de Sousa, E, Fowler, M & Swarbrick, GE 2015, 'Importance of monitoring temperature in the improvement of groundwater models — an example from an open pit mine in Papua New Guinea', in PM Dight (ed.), Proceedings of the Ninth Symposium on Field Measurements in Geomechanics
, Australian Centre for Geomechanics, Perth, pp. 501-509, https://doi.org/10.36487/ACG_rep/1508_34_deSousa
Although the use of temperature data in groundwater studies is well-established, temperature measurements are somehow underutilised or neglected in mining hydrogeology. Groundwater models, when calibrated solely with head data, often lead to non-unique solutions, providing similar head distributions as long as the ratios between permeabilities and boundary flows are preserved. The use of temperature data provides an environmental tracer and a proxy for heat and water mass balance, constraining the model parameters and increasing model reliability.
A case study from an open pit mine in Papua New Guinea is presented to illustrate the value of temperature measurements. As part of the geotechnical programme, pore pressures and temperatures have been monitored since beginning of mining using vibrating wire piezometers (VWPs). The monitoring of vertical temperature profiles identified the interplay between deep geothermal upflows and lowtemperature rainfall infiltration.
Parameter inversion has been undertaken to estimate rates of geothermal upflow and rainfall infiltration. northeastern portions of the area present lower temperatures close to the surface, resulting from higher rainfall infiltration.
The use of temperature measurements not only increased the confidence on the groundwater model parameters, but was also instrumental for the mapping of dual-phase (steam) zones, which is critical for the understanding of the pore pressure distributions.
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