PhD opportunities

Probabilistic approach in hydrogeophysics to better articulate geophysical data with hydrogeological models

Thesis proposal

Area of expertiseGeoscience and Geoengineering
Doctoral SchoolGRNE - Géosciences, Ressources Naturelles et Environnement
SupervisorMme Alexandrine GESRET
Research unitGeosciences
ContactRIVIERE Agnès
Starting dateOctober 1st 2021
Keywordshydrogeophysics, uncertainty propagation, geophysical data, hydrodynamic models, unsaturated flow, critical zone; seismic methods
AbstractThis project focuses on understanding the hydrogeology of the Critical Zone (CZ). This most heterogeneous and complex region of the Earth ranges from the vegetation top to the aquifer bottom, with a highly variable thickness [e.g.. www.ozcar-ri.org ; https://www.youtube.com/watch?v=8gW-Vy7zFdU]. The strategic importance of CZ for global water, food and energy security resources are increasingly recognized in a context of changing climate and human development. Obtaining the components of the water cycle remains a challenge, both in terms of accuracy and budget closure in the exchange fluxes through the CZ.
The knowledge of the CZ, its physical properties (hydraulic conductivity, porosity and associated parameter) and its water content dynamics (permanent and transient states) are essential to describe and simulate the bio-geochemical-physical processes involved. The resolution of flow and transport problems in the CZ suffers from (1) limited knowledge of the heterogeneities of its porous media; and (2) sparse and local direct observations to calibrate models. The water flow, matter and energy transport are therefore estimated with high uncertainties (which are quantified by stochastic methods). As a countermeasure, hydrogeophysics provides a suite of tools that limit these uncertainties and the equifinality (non-unicity of the parameters setup) affecting hydrogeological modeling. The development of innovative geophysical methods combined with hydrogeological and geotechnical measurements, have improved the spatial and temporal characterization of the physical parameters of the porous medium and, consequently, the evolution of infiltration processes and preferential flow paths within the CZ. This articulation between data and methods is encouraging, but efforts should be made to improve the quantification and estimation of the spatial and temporal resolutions of the physical parameters and their associated uncertainties. This PhD project takes advantage of available databases (geophysical and hydrogeological, e.g. http://hplus.ore.fr/en/) and associated simulations to: (1) characterize how uncertainties propagate from geophysical data (field observation) to the models (according to the methods used and the contexts); (2) question the articulation between estimations derived from these geophysical models and the hydrogeological models parametrization; adapt or revise direct geophysical problems to better satisfy modeling objectives; (3) Estimate the relevance of the information transferred from geophysical models to hydrogeological models and the associated propagation of uncertainties in order to obtain more reliable calibrations.
ProfileWe are looking for highly motivated doctoral candidates to join our project dealing with the hydrogeological and geophysical characterization. Candidates must have obtained or be in the process of obtaining a master's degree in a field related to geophysics and/or quantitative hydrogeology and/or engineering or applied mathematics. A good background in statistics, probability, mechanics and wave propagation, or even petrophysics is desirable. Experience in data analysis, information processing (signal processing, inverse problems), numerical modeling, and programming (Fortran/C; Python/Matlab) will be advantageous. Teamwork and good communication skills are essential. Written and verbal communication skills in English are required. The duration of a PhD is very short: ability of quick familiarization with new topics and strong motivation to produce results are necessary (mobility, autonomy). Outstanding candidates should apply by email to agnes.riviere@mines-paristech.fr; alexandrine.gesret@mines-paristech.fr; ludovic.bodet@sorbonne-universite.fr with a letter of motivation, a curriculum vitae, full transcripts of Bachelor and Master studies, and at least two references (with up to date contacts). Short-listed candidates will be interviewed.
FundingConcours pour un contrat doctoral
PartnershipLa thèse pourra bénéficier de soutiens en ressources propres de l’UMR METIS, de l’équipe géophysique associée H+ et de CRITEX/OZCAR pour les activités expérimentales éventuelles.