Print Email Facebook Twitter Time-lapse GPR full-waveform inversion to monitor heat tracers at the Krauthausen test site Title Time-lapse GPR full-waveform inversion to monitor heat tracers at the Krauthausen test site Author Mueller, Brianna (TU Delft Civil Engineering & Geosciences) Contributor van der Kruk, Jan (mentor) Klotzsche, Anja (graduation committee) Degree granting institution Delft University of TechnologyRheinisch-Westfälische Technische HochschuleIdea League Programme Applied Geophysics | IDEA League Date 2023-08-25 Abstract Understanding solute and heat transport processes in aquifers is crucial for monitoring and protecting the groundwater critical zone. Crosshole ground-penetrating radar (GPR) is a useful method for enhancing transport characterization in aquifers. Particularly, GPR full-waveform inversion (FWI) can provide subsurface images with resolution at the subwavelength scale, making it a well-suited method for monitoring tracer plumes. While previously applied to a salt tracer test, its effectiveness for other tracer types with differentconductivity and permittivity contrasts remains unexplored. Here, we apply this method to two tracer tests conducted at the Krauthausen test site in northwest Germany: (1) a natural gradient heat tracer test and (2) a forced-gradient combined heat-salt tracer test. Both tracers use hot water, which provides a contrast in both electrical conductivity and dielectric permittivity with the groundwater. This should permit improved monitoring capabilities with GPRFWI in comparison to the salt tracer, which only provides a contrast in electrical conductivity. However, this comes with new challenges in the processing workflow, specifically, in the starting model strategy. The results illustrate that using the ray-based permittivity tomogram anda homogeneous conductivity as FWI starting models for each time-lapse dataset is the best strategy. Additionally, we applied an amplitude analysis approach to improve the starting model in regions with low ray coverage. The effects of the heat tracer were detected over the entire depth range of the aquifer, from 3-11 m, and especially at mid-aquifer depths from 6-8.5 m. For the heat-salt tracer, we were able to detect separate effects from the salt and heat: the salt was observed at depth in the aquifer, in accordance with the salt tracer test, and theheat was observed approximately two days after the salt effects at mid-aquifer depths (from 5.5-7.5 m). In regions where minimal effects from the tracer were observed, specifically for the heat tracer, the consistent results between independent time-lapse datasets demonstrate the repeatability of the method, indicating the suitability of GPR FWI for hydrogeophysical time-lapse studies. Subject FWIGPRHydrogeophysicsMonitoring|GeophysicsHeat transportGroundwater tracer To reference this document use: http://resolver.tudelft.nl/uuid:fd4aa48e-f12a-451b-8187-81ea42ebb01f Part of collection Student theses Document type master thesis Rights © 2023 Brianna Mueller Files PDF IDEA_league_MSc_thesis_RWTH.pdf 31.29 MB Close viewer /islandora/object/uuid:fd4aa48e-f12a-451b-8187-81ea42ebb01f/datastream/OBJ/view