Siavashani N. S. auteur aut IRD Valdes-Abellan J. auteur aut IRD Do Frédéric auteur aut IRD Jimenez-Martinez J. auteur aut IRD Elorza F. J. auteur aut IRD Candela L. auteur aut IRD Serrat-Capdevila A. auteur aut IRD text journalArticle eng text/pdf born digital access The Chari-Baguirmi region, southeastern of the Lake Chad (Africa), has a wide naturally occurring piezometric depression with values deeper than the expected regional groundwater level. To date, the most widely accepted hypotheses to explain its origin and dynamics are based on lack of rainwater infiltration and exfiltration processes. The code HYDRUS-1D is applied to numerically simulate the hydrological flow processes along the unsaturated zone in two soil profiles located in the central part and on the boundary of this piezometric depression under bare and vegetated soil coverage. The simulated time period is 2004-2015 with 715 mm annual rainfall average. The computed recharge with respect to total precipitation accounts for 21% on the boundary and 12% in the central part, which is limited by thick silty low permeability layer on the top surface. Considering modelling uncertainty and limitations under the simulated climatic conditions, the rainfall effect is observed only at upper soil layers, which leads to low aquifer recharge, while the upward water flux causing water table evaporation is very low. Past climate conditions, capable of developing a drying front to reach the water table after thousands of years of drying and geological structural constraints, may explain the current depressed area. specialized Hydrus 1D Vadose zone Piezometric depression Chari Baguirmi TCHAD ZONE SOUDANOSAHELIENNE 072 020 82 19 444 [16 p.] 2023 1866-6280 https://www.documentation.ird.fr/hor/fdi:010090237 10.1007/s12665-023-11100-0 1866-6280 [F B010090237] https://www.documentation.ird.fr/hor/fdi:010090237 https://www.documentation.ird.fr/intranet/publi/2023-11/010090237.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2023-11-10 2023-11-10 fdi:010090237 fre