Comparison of three arrays in time-lapse ERT: Simulation of a leachate injection experiment

Leachate recirculation in bioreactor needs a careful optimization of water content and thus, the knowledge of the leachate plume geometry. Time-lapse Electrical Resistivity Tomography (ERT) is widely use for this purpose. However, in some situations, artefacts of ERT imaging can occur with classical inversion parameters. Using numerical modelling (simulating a 2D infiltration experiment) and standard inversion parameters, this study shows that artefacts may occur using common symmetrical elec..

Comparison of three arrays in time-lapse ERT: Simulation of a leachate injection experiment

International audienc

Reconnaissance volcano-structural de la phase ante caldeira du volcan Fogo, Iles du Cap Vert

National audienc

Volcano-structural investigations in Fogo caldera, Cape Verde Islands. Workshop on Collapse Calderas

International audienc

TDEM survey in heterogeneous volcanic aquifers: correlation between basic one dimensional models and hydrogeological data at 15 borehole test sites of Reunion Island

International audienc

Une approche multidisciplinaire pour la connaissance d’un glissement-coulée dans les marnes noires du Callovien-Oxfordien (Super Sauze, Alpes-de-Haute-Provence, France).

International audienc

Une approche multidisciplinaire pour la connaissance d’un glissement-coulée dans les marnes noires du Callovien-Oxfordien

Dans le bassin de Barcelonnette, le glissement-coulée de Super-Sauze s’est développé dans un bassin torrentiel de marnes noires callovo-oxfordiennes érodé en ravines et échines coaslescentes. Sur ce site naturel, mais complexe et difficile d’accès, une approche multidisciplinaire a associé une analyse géomorphologique couplée à un traitement photogrammétrique numérique, une prospection géotechnique (sondages et essais in situ et en laboratoire) et une investigation géophysique (méthodes de mesure de la résistivité électrique (électrique par courant continu et TDEM-time-domain electro-magnetism), sismique réfraction, Slingram. Les comparaisons, ajustements, validations des résultats complémentaires ont permis de reconstituer l’évolution historique du mouvement, de proposer un modèle conceptuel d’évolution, de définir la position et forme de la paiéotopographie, la structure interne de la coulée de débris dans la zone d’accumulation et dans la zone d’ablation avec des ordres de grandeur de précision tout à fait satisfaisants. Il est maintenant possible d’envisager la modélisation du comportement dynamique de ce type de coulée de débris, fréquent dans les Terres noires (thèse J.-P. Malet en cours) en relation avec les conditions hydrodynamiques. L’objectif est d’évaluer la probabilité de transformation rapide, de tout ou partie de la masse instable, en coulées boueuses ou en laves torrentielles

Chemical and physical weathering in the Kabini river basin, South India

Chemical and physical weathering in the Kabini river basin, South Indi

Water balance modelling in a tropical watershed under deciduous forest (Mule Hole, India) : regolith matric storage buffers the groundwater recharge process

Accurate estimations of water balance are needed in semi-arid and sub-humid tropical regions, where water resources are scarce compared to water demand. Evapotranspiration plays a major role in this context, and the difficulty to quantify it precisely leads to major uncertainties in the groundwater recharge assessment, especially in forested catchments. In this paper, we propose to assess the importance of deep unsaturated regolith and water uptake by deep tree roots on the groundwater recharge process by using a lumped conceptual model (COMFORT). The model is calibrated using a 5 year hydrological monitoring of an experimental watershed under dry deciduous forest in South India (Mule Hole watershed). The model was able to simulate the stream discharge as well as the contrasted behaviour of groundwater table along the hillslope. Water balance simulated for a 32 year climatic time series displayed a large year-to-year variability, with alternance of dry and wet phases with a time period of approximately 14 years. On an average, input by the rainfall was 1090 mm year(-1) and the evapotranspiration was about 900 mm year(-1) out of which 100 mm year(-1) was uptake from the deep saprolite horizons. The stream flow was 100 mm year(-1) while the groundwater underflow was 80 mm year(-1). The simulation results suggest that (i) deciduous trees can uptake a significant amount of water from the deep regolith, (ii) this uptake, combined with the spatial variability of regolith depth, can account for the variable lag time between drainage events and groundwater rise observed for the different piezometers and (iii) water table response to recharge is buffered due to the long vertical travel time through the deep vadose zone, which constitutes a major water reservoir. This study stresses the importance of long term observations for the understanding of hydrological processes in tropical forested ecosystems