Research

 I am mostly focused on observing, understanding, and modeling water storage in the different compartments of the critical zone (defined on a vertical from the impermeable bedrock to the top of canopy) in West-Africa to help define its sensitivity to global changes (i.e. anthropic + climate).

I have mostly worked on the analysis and quantification of processes which drive the water budget at different scales (time & space), with a focus on the storage component. Being from both geophysics and hydrology background, and being accustomed to acquire, process and handle data of very different kinds for processes analyses and modeling, I could work on

1. developing original methods for distributed caracterization and monitoring of the underground, including water storage variations and spatialization of hydrodynamic properties,
2. operating hydrological and geophysical data fusion leading to
3. multi-scale analyses and modeling of critical zone processes.

Moving now to the spatial scales of water resources management and risk mitigation, I try to build up on my background to conduct both heterogeneous data fusion and hyperresolution critical zone modeling to bring answers to the hydrological functioning of the critical zone at these scales, in West-Africa.

After several internships around the theme of Risks, mostly in vulnerable regions (Glacial lake outburst floods in Nepal, mega-landslide assessment in Mexico, rock mechanics during landslides in New Zealand), I did my master work on Earthquakes Early Warning by developing rapid & automatic seismic event detection and location algorithms at the Institut de Physique du Globe de Strasbourg (IPGS), always motivated by developing a research mostly applied to societal needs.

I then moved on to hydrology-related risks and resources assessment by working at the IRD as an engineer on aquifer recharge estimates in semi-arid areas (Tchad lake area, East-Niger). I combined hydrological, geophysical and gravimetric surveys together with hydrological modeling (MODFLOW) to estimate sedimentary aquifer recharge by the Komadougou Yobé, the only Sahelian river contributing to the endoreic Tchad lake (see Genthon, Hector, et al., 2015).

I did my PhD on Multi-scale hydrogeophysical caracterisation and water storage dynamics in a hardrock basement catchment of a sudanian area (Benin): contribution from gravimetry. I showed that measuring water storage changes (by gravimetry, among others), helped to:

• better constrain hydrological budgets,
• better calibrate mathematical, conceptual, and physically-based hydrological models,
• identify underground water transfers and baseflow generation processes (Hector et al., 2015),
• better determine aquifer storage properties (i.e. specific yield) in highly heterogeneous hard-rock basement areas (Hector et al., 2013), and finally
• (could help to) measure evapotranspiration, if a rigorous experiment protocol could be set in place. More details in Hector et al., 2014.

While some of the results have been published, all of them can be found in the manuscript (which contains subsections and captions in English).

To get there, I did three things:

• There was a need to develop specific processing techniques for gravity data, including regional hydrological or atmospheric loading corrections (Hinderer, Hector et al., 2014), and instrumental effects, in order to obtain gravity residuals associated to local hydrology (Hector et al., 2014).
• I analysed together water storage changes measurements with a large number of observations of hydrological variables (water table depths, streamflow, soil moisture, evapotranspiration...) and of the physical environment (hydrodynamic properties, geophysical imagery, geological maps...) (Hector et al., 2013, 2015).
• I used or developed mathematical, conceptual and physically-based (HYDRUS-1D) models to conduct sensitivity analysis, which helped me to identify scale controls and interdependencies of different scales (i.e., a plot scale -a few tens of meters, the footprint of gravity measurements- was being strongly affected by the larger, hillslope scale, which controled lateral transfers toward the catchment outlet and higher-evapotranspiration downslope trees). I finally used a fully coupled critical zone model (ParFlow-CLM), to represent hydrological processes at their observation scale.

1) There was a strong need to homogenize relative micro-gravity processing codes, to enhance reproducible research in microgravimetry. So far, every team were using their own codes. To work on this, and motivated by the huge dataset acquired during my PhD, which needed simplified processing tools, I asked for a research contract at the LABEX G-EAU-THERMIE in Strasbourg, to develop a suitable tool. This gave birth to pyGrav, an open-source platform for processing microgravity data (Hector & Hinderer, 2016).

2) I now work on modeling the critical zone at different spatial scales, to get closer to the scales of water resources management and risk mitigation. Motivated by the will to bring answers to the hydrological functioning of the critical zone at different scales, in West-Africa, I am now conducting sensitivity experiments on small scale ParFlow-CLM model for an inland valley, to derive the hydrological functionning of such fundamental landscape feature in West Africa (Hector et al., in prep.).

Also, I develop methods to spatialize subsurface hydrodynamic properties, to help feeding critical zone models, but also to provide products for partners in West Africa (regional centers, national research & operational institutions, Universities, NGOs). Among others, I am interested in surface temperature remote sensing products for mapping proxys of subsurface behaviors.

To develop my research, I mostly rely on the AMMA-CATCH observatory and West-African partners. This hydro-meteorological observatory composed of three meso-scale sites (Mali, Niger and Benin) has the particularity to sample both an eco-climatic and a geologic gradient across West-Africa. Highly instrumented critical zone sections in each sites allow to experience new observation methods, to infer critical zone processes or to test models. Particularly, it helps to define method to regionalize parameters, state variables, or processes, based on remote sensing data trained on these local sites, for instance, or any spatial surrogate, such as geological maps.