Présentations Colloques

    Session 5.01: Groundwater resources in a world facing climate change
    Hector (orateur)
    Global changes impacts on water fluxes of the critical zone for the sudanian area in West-Africa
    West-Africa undergoes global changes which affect water redistribution within its critical zone (CZ). Particularly, strong demographic rates (about 3%) have implied rapid changes in land use and land cover (LC) in the past, which continue nowadays. Climate has also changed significantly, with a marked drought starting in the 70’s-80’s and, at least over the Sahel, significant evolution in precipitation temporal distributions.****The consequences of these global changes on water fluxes (discharge, recharge, evapotranspiration) within the CZ are not well known for the hard rock aquifers of the subtropical sudanian area, both in past conditions and for the future. Overall, it has been observed that discharge has decreased in sudanian climate since the 80’s, but the impact on other fluxes and groundwater storage is not known.****In this presentation, we aim at addressing the issue of the impacts of LC changes on water fluxes of a 13000kmC sudanian catchment in northern Benin, using a physically-based critical zone model (ParFlow-CLM). This model simulates flow in saturated and unsaturated zones (ParFlow) and couples the energy and water cycles through a land surface scheme (CLM). Model simulations are compared to the observations from the long-term AMMA-CATCH observing system to diagnose model performance. Specific targets are the lower evapotranspiration observed over herbaceous fallows and associated shallower water table as compared to woody cover. ****We are interested in simulating the impact of past LC changes, given the observed precipitation inputs, and at running sensitivity experiments with LC changes for the future. We are particularly interested in the space-time evolution of the river-water table connections which are expected to produce non-linear and step-like system responses.


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