Jean-Christophe Maréchal

French Geological Survey | BRGM · Direction Eau, Environnement, et Ecotechnologies

A water budget approach is developed to jointly estimate specific yield and natural recharge in an unconfined aquifer with significant seasonal water table fluctuations. Water table fluctuations are due to distinct seasonality in groundwater recharge. The separation of the hydrologic year into two (or more) extended seasons of recharge (wet season)...

The hydrodynamic properties of the weathered-fractured layer of a hard-rock pilot watershed in a granitic terrain are characterized using hydraulic tests at different scales. The interpretation of numerous slug tests leads to characterize the statistical distribution of local permeabilities in the wells. The application of flowmeter profiles during...

Pumping tests carried out in the fissured layer of a granitic hard-rock aquifer, interpreted at the observation wells by means of the analytical solution of Neuman and at the pumping wells with that of Gringarten show the existence of a strong vertical anisotropy of this layer of the aquifer; the horizontal permeability is clearly and systematicall...

Deep drilling of borewells to hundreds of meters – depth is increasingly frequent for water exploration in fractured crystalline rocks. At the same time, many studies provide evidence that hard-rocks areas are characterized by a shallow higher-permeability zone (‘‘active'' zone) that overlies a deeper lower-permeability zone hosting little flow (‘‘...

The weathered layers of crystalline rocks form aquifers that are of prime interest for water supply in hard rock areas. These weathering profiles generally develop under both stable geodynamic conditions (weathering rate ≫ erosion rate) and a hydrolysing climate. They are composed of thick stratiform layers that follow the paleo-landscape (paleotop...

In semi‐arid regions as in India, where agriculture relies on groundwater abstraction, increase of water resources availability through managed aquifer recharge (MAR) or rainwater harvesting (RWH) is often perceived as a major solution. Studies on these structures efficiency exists but despite the interest, limited information is available on the t...

On atoll islands, the fresh water lens (FWL) constitutes, for the island population, a very important fresh water resource for various usages. Its shape and thickness highly depend on the underground characteristics of several rock formations which constitute the underground of the island: upper Holocene sediments and lower Pleistocene limestone ro...

GRACE (Gravity Recovery and Climate Experiment) and its follow-on mission have provided since 2002 monthly anomalies of total water storage (TWS), which are very relevant to assess the evolution of groundwater storage (GWS) at global and regional scales. However, the use of GRACE data for groundwater irrigation management is limited by their coarse...

Les eaux souterraines – outil de lutte contre la pauvreté Après les famines des années 1950, l’Inde a mené une politique agricole très volontariste de façon à atteindre l’autosuffisance alimentaire. Les gains de productivité acquis au moyen de la modernisation des techniques agricoles et de l’utilisation d’intrants (engrais, pesticides et irrigati...

Description of an extensive method for the validation of GRACE-derived downscaled GWS with in situ data

Managed aquifer recharge (MAR) is a widely accepted technique for augmenting groundwater supplies for potable and mitigating salt water intrusion in coastal aquifers highly pumped for several usages. This is the case of the Gapeau aquifer located close to Hyères city, South of France, were the full-scale Aquarenova scheme launched in the 2010s by S...

GRACE (Gravity Recovery and Climate Experiment) and its follow-on mission have provided since 2002 monthly anomalies of total water storage (TWS), which are very relevant to assess the evolution of groundwater storage (GWS) at global and regional scale. However, the use of GRACE data for groundwater irrigation management is limited by their coarse...

We present a new set of analytical solutions for analysing pumping tests in a well near a vertical fault zone, dyke or vein. We consider a fault zone with finite width, storativity and hydraulic conductivity, which can be anisotropic, and without limitation of the diffusivity contrast between the three aquifer domains (pumped aquifer, fault zone an...

Heat as a tracer in fractured porous aquifers is more sensitive to fracture‐matrix processes than a solute tracer. Temperature evolution as a function of time can be used to differentiate fracture and matrix characteristics. Experimental hot (50 °C) and cold (10 °C) water injections were performed in a weathered and fractured granite aquifer where...

Modelling of heterogeneous aquifers, such as crystalline aquifers, is often difficult and, flow and transport predictions are always uncertain, suffering of our imperfect knowledge of the spatial distribution of aquifer parameters. This paper aims to test the robustness of a first-order hydraulic conductivity map estimated from both a detailed wate...

Despite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi‐arid and sub‐humid climates, due to the difficulty of estimating hydro‐geochemical balanc...

Simultaneously acquiring time series of climate, hydrology and hydrochemical data over decades on river systems is pivotal to understand the complex interactions involving rock, soil water, air and biota in the Critical Zone, to build integrated modeling and to propose predictive scenarios. Among the Critical Zone Observatories (CZOs) implemented i...

The behaviour of transient groundwater mounds in response to infiltration from surface basins has been studied for decades, but some common settings still lack analytical solutions. It has been shown that applying mathematical integration to the line-sink solution developed by Hantush in the 1960s for pumping an unconfined aquifer, considering rech...

Les aquifères jouent un rôle important pour la fourniture de plusieurs services aux activités humaines. Ils sont pourtant pour le moment peu pris en compte dans les démarches d’évaluation de services écosystémiques, et de conception des solutions fondées sur la nature. Cet article propose un cadre conceptuel permettant d’articuler aquifères, servic...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

This chapter describes the status of groundwater resources in France. French geology consists of a large variety of rock types, resulting in very different types of aquifers ranging from sedimentary basins, alluvial plains, limestone rocks, and crystalline rocks. Today, groundwater resources represent about 66% of Frances’s domestic water supply, 3...

Managed aquifer recharge (MAR) constitutes a potential and promising solution to deal with several water management issues: water shortage, water level depletion, groundwater pollution, and saline water intrusion. Among others, the proper siting and cost evaluation of such a solution constitutes sources of uncertainty for the implementation of MAR...

Drops loaded in calcium ions detach from stalactites and impact the underlying stalagmites, thereby allowing these latter to grow through calcite precipitation. Nevertheless, little is known about the influence of the drop free fall and splash dynamics on stalagmite shape and width. Through high-speed imaging of impacting drops on stalagmites from...

Inner boundary conditions describe the interaction of groundwater wells with the surrounding aquifer during pumping and are associated with well‐skin damage that limits water production and water derived from wellbore storage. Pumping test evaluations of wells during immediate and early‐time flow require assignment of inner boundary conditions. Ori...

Although karst aquifers represent a widespread groundwater resource in Europe, there is no unified classification and each country has adopted his own typology, taking into account the characteristics of their own karst aquifers. The main objective of the CHAKA (CHAlk and KArst) work package, part of the GeoERA RESOURCE project (http://geoera.eu/pr...

Robust transport simulations for sustainable management of groundwater in fractured rocks, need accurate observation data about fracture and matrix processes. In aquifers with naturally hot groundwaters (i.e., 30 ºC in South India), heat injections can become difficult and cumbersome, considering strong density influences. Injecting cold water is a...

Les aquifères jouent un rôle important pour la fourniture de plusieurs services aux activités humaines, parmi lesquels le stockage et la production naturelle d’eau de qualité (pour l’approvisionnement en eau potable, l’irrigation, …), l’alimentation en eau des milieux aquatiques associés, la régulation des inondations, mais également la géothermie...

Physics-based modeling of karst systems remains almost impossible without enough accurate information about the inner physical characteristics. Usually, the only available hydrodynamic information is the spring discharge at the karst outlet. Numerous works in the past decades have used and proven the usefulness of time-series analysis applied to sp...

With following the enclosed link to YouTube, you are invited to watch a video about smart temperature tracing with hot and cold water injections in India: https://www.youtube.com/watch?v=cx6s4cGj1sc

Despite its financial and ecological benefits, the contribution of MAR to safe water supply at global scale is still limited due to various reasons. Especially the lack of data on associated risks and the absence of proper monitoring at some MAR facilities reduces the level of public trust, raises questions about the impact of MAR on the affected e...

Karst aquifers andwatersheds represent amajor source of drinkingwater around the world. They are also known as complex and often highly vulnerable hydrosystems due to strong surface–groundwater interactions. Improving the understanding of karst functioning is thus a major issue for the efficient management of karst groundwater resources. A comprehe...

Karst aquifers are characterized by complex and often highly non-linear hydraulic and transfer responses. Generally, the only information that can be obtained are the precipitations on a watershed and the spring discharge, at the karst system output. Numerous works in the past decades have used and proven the usefulness of time series analysis and...

The French critical zone initiative, called OZCAR (Observatoires de la Zone Critique–Application et Recherche or Critical Zone Observatories–Application and Research) is a National Research Infrastructure (RI). OZCAR-RI is a network of instrumented sites, bringing together 21 pre-existing research observatories monitoring different compartments of...

Multiscale and long-term work is needed to tackle the scientific challenges found in areas vulnerable to climate change and anthropic pressure. This is the case in the semiarid and drought-prone regions of southern India where freshwater is scarce and agriculture near fast-growing cities is triggering high water demand. The Indo-French Center for G...

Karst systems present particular hydrography and hydrology, and are characterized by a non-negligible spatial heterogeneity of hydraulic parameters (such as rock permeability, storage coefficient…). The dual character of karst flow system is widely recognized and stems from the existence of different types of porosities within karst aquifer, which...

To overcome water scarcity issues, Managed Aquifer Recharge (MAR) structures are currently developed in many parts of the world, including poorly permeable terrain like weathered crystalline rocks. In such geological context, characterized by relatively limited groundwater storage mainly associated with fractures located at the interface between th...

The sources of REY-Th-U and long-term mass balance were assessed in the gneissic tropical forested Critical Zone Observatory of Mule Hole, India. The study relies on the characterization of the solid compartments (bedrock, soils, streambed and suspended sediments), on batch leaching experiments of the parent gneiss and on extractions of cation-exch...

Karst systems present particular hydrography and hydrology, and are characterized by a non-negligible spatial heterogeneity of hydraulic parameters (such as rock permeability, storage coefficient…). The dual character of karst flow system is widely recognized and stems from the existence of different types of porosities within karst aquifer, which...

Due to the duality in terms of (1) the groundwater flow field and (2) the discharge conditions, flow patterns of karst aquifer systems are complex. Estimated aquifer parameters may differ by several orders of magnitude from local (borehole) to regional (catchment) scale because of the large contrast in hydraulic parameters between matrix and condui...

The behaviour of transient flow due to pumping in fractured rocks has been studied for at least the past 80 years. Analytical solutions were proposed for solving the issue of a well intersecting and pumping from one vertical, horizontal or inclined fracture in homogeneous aquifers, but their domain of application—even if covering various fracture g...

Physics-based modeling of karst systems remains almost impossible without enough accurate information about the inner physical characteristics. Usually, the only available hydrodynamic information is the flow rate at the karst outlet. Numerous works in the past decades have used and proven the usefulness of time-series analysis and spectral techniq...

The source and proportion of REY, Th and U exported by groundwater and by the ephemeral stream along with the elemental proportions passing through vegetation have been assessed in the sub-humid tropical forested CZO of Mule Hole, Southern India. The study relies on a pluri-annual hydro-geochemical monitoring combined with a hydrological model. The...

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Groundwater can represent a boundary condition for the dynamics of water into the critical zone. Groundwater level fluctuations influence several hydrodynamic and geochemical processes in the non-saturated zone such as, droughts and floods, rock-water interactions, surface water and soils quality, climate variability and change impacts… Several dif...

In fractured media, solute transport is controlled by advection in open and connected fractures and by matrix diffusion that may be enhanced by chemical weathering of the fracture walls. These phenomena may lead to non-Fickian dispersion characterized by early tracer arrival time, late-time tailing on the breakthrough curves and potential scale eff...

Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with a strong structural complexity, which is rarely characterized in detail or robustly. This research focused on a CT...

Sentinel-1 (S1) radar and Sentinel-2 (S2) optical detections of agricultural areas allow spatio-temporal monitoring of crop growth and surface water dynamics since 2015 at the global scale. This project have explored two ways of exploiting these newly data at high spatial and temporal resolution (respectively 10-20 meters and 5-10 days): 1- the lon...

An innovative approach for regionalizing the 3-D effective-porosity field is presented and applied to two large, overexploited and deeply weathered crystalline aquifers located in southern India. The method derives from earlier work on regionalizing a 2-D effective-porosity field in that part of an aquifer where the water table fluctuates, which is...

Crystalline thermo-mineral and carbo-gaseous (CTMCG) hydrosystems are well known for their economic importance in fields such as thermal, spa activities and natural mineral water (NMW) bottling. Such systems are usually associated with strong structural complexity, which is rarely characterised in detail or robustly. This research focuses on a CTMC...

A numerical discrete conduit-continuum model is employed to investigate large-scale groundwater abstraction in karst aquifers. The application of large-scale experiments is one approach to deal with the scale problem in hydraulic parameter assessment, caused by significant contrasts of hydraulic parameters in a karst aquifer. Here, conduit drawdown...

In the context of global changes and population growth, agricultural activities are a growing factor influencing water resources availability in term of quantity and quality. Water management strategies have to be analyzed at a regional catchment scales. Yet, agricultural practices, crop water and nutrient consumption that drive the main water and...

Several methods can be used to estimate groundwater recharge. These vary in terms of time scale and the nature of the data they treat. ESPERE, an MS Excel application, uses several different commonly-used methods to rapidly and simultaneously estimate recharge. It makes it possible to quantify recharge with a monthly and annual time step and to vis...

The recharge flow paths in a typical weathered hard-rock aquifer in a semi-arid area of southern India were investigated in relation to structures associated with a managed aquifer recharge (MAR) scheme. Despite the large number of MAR structures, the mechanisms of recharge in their vicinity are still unclear. The study uses a percolation tank as a...

Managed aquifer recharge (MAR) through percolation tanks is a promising technique to increase local water availability. However, authors such as Dillon et al. (2009) point out the lack of data available for an accurate assessment and note that little evidence exists on the positive impact at local scale. Some authors even point out the possible neg...

The Saint-Galmier (Massif central, France) CO2 rich natural mineral waters are known and drunk at least since the Roman times and are bottled since more than two centuries under the "Badoit" sparkling mineral water brand (Danone Group). A synthesis, processing, and interpretation of a large data set from this hydrogeological area has been performed...