Thesis defense of Behzad Pouladi

The use of heat for subsurface flow quantification and understanding the subsurface heterogeneity

The heterogeneity of subsurface media and variability of hydraulic conductivity controls groundwater flow and contamination transport in aquifers. Here, several complementary approaches are developed to used heat to better constrain subsurface flow and reconstruct the subsurface heterogeneity. A typical approach for reconstruction of hydraulic conductivity values and their spatial distribution is hydraulic tomography relying on the inversion of hydraulic head data. In this work, we first assess the advantages of groundwater flux data (inferred by using Active Fiber Optic Distributed Temperature Sensors (A-FO DTS)) in a synthetic hydraulic tomography test. Next, we design and implement the first hydraulic tomography experiment measuring groundwater head and flux data simultaneously in a shallow granular aquifer at Saint-Lambert site close to Québec city, Canada. The results from numerical studies reveal that flux data outperforms the head data for a small number of observations while for the high number of observations, the reconstructed heterogeneity is independent of the data type. The results from the hydraulic tomography experiment show the advantage of including a high number of measured flux obtained by A-FO DTS leads to a reduction of uncertainty estimation. Finally, the passive DTS is used to monitor groundwater flow in an artesian fractured borehole at  Ploemeur site in Brittany. The results unveil the potential of passive DTS for capturing the groundwater dynamics in fractured media.

Keywords: Heat, DTS, Flux and Subsurface Flow, Heterogeneity, Hydraulic tomography


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