Long-term rise in a Sahelian water-table: the Continental Terminal in South-West Niger
2001
Leduc, C | Favreau, Guillaume | Schroeter, P | Institut de Recherche pour le Développement (IRD) | Gestion de l'Eau, Acteurs, Usages (UMR G-EAU) ; Centre de Coopération Internationale en Recherche Agronomique pour le Développement (Cirad)-Bureau de Recherches Géologiques et Minières (BRGM)-Institut de Recherche pour le Développement (IRD)-AgroParisTech-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Institut Agro Montpellier ; Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro)-Institut national d'enseignement supérieur pour l'agriculture, l'alimentation et l'environnement (Institut Agro) | Hydrosciences Montpellier (HSM) ; Institut de Recherche pour le Développement (IRD)-Université Montpellier 2 - Sciences et Techniques (UM2)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) | Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF) | ORSTOM | Institut des Géosciences de l’Environnement (IGE) ; Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (Fédération OSUG)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP) ; Université Grenoble Alpes (UGA)
International audience
Afficher plus [+] Moins [-]anglais. The Continental Terminal water-table near Niamey (S-W Niger) has been the subject of a dense and detailed survey conducted over a period of almost 15 yr. The continuous rise in the groundwater level was unexpected but manifest and varied between 0.01 and 0.45 m yr(-1). As shown by corroborating measurements made throughout the twentieth century, this rise has been taking place for much longer and present levels are the highest ever recorded. Since the beginning of the 1960s, groundwater resources have increased by up to 150% (+15% on median), in spite of the severe droughts of the 1970s and 1980s. Based on isotopic data, infiltration is estimated at around 5 mm yr(-1) for median over the long-term. Hydrodynamic observations show that in recent years it has exceeded 20 mm yr(-1). The rise acceleration during the past decade is apparent from groundwater level chronicles. Even if fluctuations in rainfall may interfere, this phenomenon is mainly explained by a change in land-use. In this semi-arid area, intense land clearing has modified the hydraulic properties of the top cm of the soil and has consequently increased surface runoff. As runoff concentrates in temporary endoreic ponds and then infiltrates to the water-table, higher runoff implies higher groundwater recharge and a subsequent rise in the water-table. This is one of the best documented examples of a long-term rise of an African water-table in such a semi-arid context.
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