Camille Bouchez

• PhD
• Researcher (CNAP) at University of Rennes

In response to the growing demand for groundwater flow models, we present HydroModPy, an open-source toolbox designed to automate their deployment at the catchment scale. Built on top of the MODFLOW-enabling FloPy library, HydroModPy combines the robust WhiteboxTools toolbox for geospatial analysis and the well-validated MODFLOW code for groundwate...

The need for predictive models increases as the pressure of global change intensifies. Regional-scale modeling of shallow unconfined aquifers (10-100 m depth) remains challenging, especially in complex basement aquifers. Controlled both by topography and geology, groundwater flows are organized from hillslope to catchment scale. It is particularly...

Plain Language Summary In ice‐free catchments, groundwater is the main water source maintaining streamflow during extended dry periods. In addition to its importance for water resources, locations where groundwater contributes to surface stream water are important hotspots where interactions between biological and chemical processes occur, that hav...

Ferriphaselus amnicola GF-20 is the first Fe-oxidizing bacterium isolated from the continental subsurface. It was isolated from groundwater circulating at 20 m depth in the fractured-rock catchment observatory of Guidel-Ploemeur (France). Strain GF-20 is a neutrophilic, iron- and thiosulfate-oxidizer and grows autotrophically. The strain shows a pr...

Despite covering only 3% of the global land surface, peatlands are an active part of the Critical Zone (CZ) exchanging large water and greenhouse gas (GHG) fluxes with the surrounding aquifers, surface waters, and the atmosphere. While ecosystem services of peatlands (carbon and water storage, buffering of local climate) are essential to address 21...

Dissolved Oxygen (DO) plays a key role in reactive processes and microbial dynamics in the critical zone. Recent observations showed that fractures can provide rapid pathways for oxygen penetration in aquifers, triggering unexpected biogeochemical processes. In the shallow subsurface, DO reacts with electron donors, such as Fe ²⁺ coming from minera...

Concentration fields of solutes in porous media often exhibit large fluctuations, driven by physical and chemical heterogeneity from the pore to the Darcy scale. For many applications, ranging from reactive transport modeling to toxicology, the knowledge of mean concentrations is not sufficient, and quantifying concentration variability is necessar...

Biogeochemical reaction kinetics are generally established from batch reactors where concentrations are uniform. In natural systems, many biogeochemical processes are characterized by spatially and temporally variable concentration gradients that often occur at scales which are not resolved by field measurements or biogeochemical and reactive trans...

The long-term fate of agricultural nitrate depends on rapid subsurface transfer, denitrification and storage in aquifers. Quantifying these processes remains an issue due to time varying subsurface contribution, unknown aquifer storage and heterogeneous denitrification potential. Here, we develop a parsimonious modelling approach that uses long-ter...

Over the last decades, Arctic landscapes have experienced intense warming leading to permafrost degradation and rapid ecosystem changes. Active layer thickening, widespread melting of ground ice and thermo-erosion have affected the mobilization of organic and mineral elements. While the carbon and nitrogen cycles are intensively studied, the soil w...

Intercomparison of surface water‐groundwater (SW‐GW) exchange fluxes at the regional scale is rarely undertaken, mainly because estimates are method and scale‐dependent and usually associated with large errors. In the present study, we compare SW‐GW exchange fluxes calculated from a multitracer mass balance in the river, an application of Darcy's l...

The Chari-Logone watershed is the only hydrologically active part of the Lake Chad Basin (Central Africa). The Chari-Logone River and Lake Chad exchange water with the surrounding unconfined aquifers of sedimentary and crystalline rock types. In this study, the groundwater contribution to stream flow was quantified by taking advantage of a comprehe...

This study assesses the worth of routinely collected hydraulic data (groundwater head, stream stage and streamflow) and lesser collected water chemistry data (Radon-222, Carbon-14, electrical conductivity (EC)) in the context of making regional-scale surface water-groundwater (SW-GW) exchange flux predictions. Using integrated SW-GW flow and transp...

Lake Chad, in the Sahelian zone of west-central Africa, provides food and water to ~50 million people and supports unique ecosystems and biodiversity. In the past decades, it became a symbol of current climate change, held up by its dramatic shrinkage in the 1980s. Despites a partial recovery in response to increased Sahelian precipitation in the 1...

The Lake Chad Basin (LCB) is one of the main endorheic basins in the world and has undergone large-level and surface variations during the last decades, particularly during the Sahelian dry period in the 1970s and the 1980s. The Chari–Logone River system covers 25% of the LCB but accounts for up to 82% of the Lake Chad water supply. The aim of this...

The lack of data and suitable methods to quantify regional hydrological processes often hinders sustainable water management and adaptation to climate change in semiarid regions, particularly in the Sahel, which is known for its climatic variability. Here we show that 36Cl from nuclear tests is a promising method to estimate water transit times and...

The fate of 28 trace organic compounds (TrOCs) was investigated in the hyporheic zone (HZ) of an urban lowland river in Berlin, Germany. Water samples were collected hourly over 17 h in the river and in three depths in the HZ using minipoint samplers. The four relatively variable time series were subsequently used to calculate first-order removal r...

At present, Lake Chad ( ~13°0 N, ~14° E) is a shallow freshwater lake located in the Sahel/Sahara region of central northern Africa. The lake is primarily fed by the Chari-Logone river system draining a ~600 000 km2 watershed in tropical Africa. Discharge is strongly controlled by the annual passage of the intertropical convergence zone (ITCZ) and...

In the Sahelian belt, Lake Chad is a key water body for 13 million people, who live on its resources. It experiences, however, substantial and frequent surface changes. Located at the centre of one of the largest endorheic basins in the world, its waters remain surprisingly fresh. Its low salinity has been attributed to a low infiltration flow whos...

In northern African tropics, it is now well established that the Last Glacial Maximum (LGM) was extremely dry followed by a wetter Holocene. Numerous palaeolake records reveal a fairly consistent pattern of a moister early Holocene resulting in a green Sahara followed by the onset of aridification about 4000 years ago. These palaeoenvironmental con...

36Cl measurements in groundwaters of the deep confined aquifer of the Lake Chad Basin (LCB) were performed in order to constrain groundwater geochemical ages and residence times. Twenty-seven wells were sampled in Nigeria, Niger and Chad in the southern parts of the large (700 000 km2) multilayered aquifer of the LCB. 36Cl/Cl values range between 1...

In the Sahelian belt, Lake Chad is a key water body for 13 million people who live on its resources. It experiences, however, substantial and frequent surface changes. Located at the center of one of the largest endorheic basins in the world, its waters remain surprisingly 5 fresh. Its low salinity has been attributed to a low infiltration flow who...

During the Holocene, that is, the last 11,500 years, the North African climate has undergone significant changes. While the Sahara is now the largest desert on Earth, there used to be a “Green Sahara” at the beginning of the Holocene. It resulted from significant precipitations that were linked to the northward shift of the inter-tropical convergen...

Le bassin endoréique du lac Tchad (BLT) couvre 2,5 millions de km2 au centre de la zone sahélienne. La distribution en eau de surface (rivières et lac) y est très inégale et variable dans l’espace et dans le temps. Le lac Tchad, dont la surface enregistre de fortes variations, agit comme un amplificateur des variations climatiques sur le BLT. Le sy...

Depots lacustres holocenes de Hassi El Medjna, Grand Erg Occidental, Algerie Au cours de l’Holocene, c’est-a-dire les 11 500 dernieres annees, le climat de l’Afrique du Nord a connu d’importants changements.Alors qu’aujourd’hui le Sahara est le plus vaste desert du monde, il y avait un « Sahara Vert » au debut de l’Holocene, du fait d’importantes p...

Estimation of lake-groundwater interactions is a crucial step to constrain water balance of lacustrine and aquifer systems. Located in the Sahel, the Lake Chad is at the center of an endorheic basin of 2,5.106 km2. One of the most remarkable features of this terminal lake is that, despite the semi-arid context and high evaporation rates of the area...

Iron oxidation at neutral pH by the phototrophic anaerobic iron-oxidizing bacterium Rhodobacter sp. strain SW2 leads to the formation of iron-rich minerals. These minerals consist mainly of nano-goethite (α-FeOOH), which precipitates exclusively outside cells, mostly on polymer fibers emerging from the cells. Scanning transmission X-ray microscopy...