1. Inverse estuaries in West Africa : evidence of the rainfall recovery ?
- Author
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Ange-Bouramanding Diedhiou, Victor Mendy, Julien Andrieu, Awa Diop, Djiby Sow, Yancouba Sané, Mamadou Thior, Jean-Pierre Vandervaere, Arame Dièye, Bamol Ali Sow, Jean-Pierre Montoroi, Safietou Soumaré, Yasmin Bouaita, Marie-Jeanne Senghor, Luc Descroix, Saloum Coly, Alexandre Badiane, Sylvie-Paméla Manga, Bakary Faty, Joseph Mingou, Eric Machu, Boubacar Demba Ba, ORSTOM, Université Assane SECK de Ziguinchor (UASZ), Laboratoire d'Algèbre, de Cryptologie, de Géométrie Algébrique et Applications (LACGAA), Université Cheikh Anta Diop [Dakar, Sénégal] (UCAD), Patrimoines Locaux et Gouvernance (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Patrimoines locaux, Environnement et Globalisation (PALOC), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU), Patrimoines et Territoires de l'eau (LMI PATEO), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Université de Lorraine - UFR Sciences humaines et sociales - Metz (UL UFR SHS), Université de Lorraine (UL), LMI ECLAIRS, Ecole polytechnique de Thiès, Ecole Polytechnique de Thiès, Université Côte d'Azur (UCA), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Direction de la Gestion et la Planification des Ressources en Eau (DGPRE), Laboratoire d'Océanographie Physique et Spatiale (LOPS), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut d'écologie et des sciences de l'environnement de Paris (iEES Paris ), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Études des Structures, des Processus d’Adaptation et des Changements de l’Espace (ESPACE), Université Nice Sophia Antipolis (1965 - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Avignon Université (AU)-Aix Marseille Université (AMU)-Centre National de la Recherche Scientifique (CNRS)-Université Côte d'Azur (UCA), 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)-Université Grenoble Alpes (UGA)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), Université Grenoble Alpes (UGA), Sorbonne Université (SU)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS), Institut de Recherche pour le Développement (IRD)-Sorbonne Université (SU)-Université Paris-Est Créteil Val-de-Marne - Paris 12 (UPEC UP12)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de Recherche pour le Développement (IRD)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP ), and UFR Sciences humaines et sociales - Metz [Université de Lorraine] (UL UFR SHS)
- Subjects
Wet season ,lcsh:Hydraulic engineering ,010504 meteorology & atmospheric sciences ,[SDE.MCG]Environmental Sciences/Global Changes ,Geography, Planning and Development ,drought ,010501 environmental sciences ,Aquatic Science ,water salinity ,01 natural sciences ,Biochemistry ,West africa ,lcsh:Water supply for domestic and industrial purposes ,lcsh:TC1-978 ,Dry season ,West Africa ,14. Life underwater ,mangrove 1 Problematics ,0105 earth and related environmental sciences ,Water Science and Technology ,Hydrology ,lcsh:TD201-500 ,geography ,mangrove ,geography.geographical_feature_category ,Estuary ,15. Life on land ,6. Clean water ,State of the Art ,Salinity ,Fresh water ,13. Climate action ,inverse estuaries ,Period (geology) ,Environmental science ,Mangrove - Abstract
In West Africa, as in many other estuaries, enormous volumes of marine water are entering the continent. Fresh water discharge is very low, and it is commonly strongly linked to rainfall level. Some of these estuaries are inverse estuaries. During the Great Sahelian Drought (1968&ndash, 1993), their hyperhaline feature was exacerbated. This paper aims to describe the evolution of the two main West African inverse estuaries, those of the Saloum River and the Casamance River, since the end of the drought. Water salinity measurements were carried out over three to five years according to the sites in order to document this evolution and to compare data with the historical ones collected during the long dry period at the end of 20th century. The results show that in both estuaries, the mean water salinity values have markedly decreased since the end of the drought. However, the Saloum estuary remains a totally inverse estuary, while for the Casamance River, the estuarine turbidity maximum (ETM) is the location of the salinity maximum, and it moves according to the seasons from a location 1&ndash, 10 km downwards from the upstream estuary entry, during the dry season, to a location 40&ndash, 70 km downwards from this point, during the rainy season. These observations fit with the functioning of the mangrove, the West African mangrove being among the few in the world that are markedly increasing since the beginning of the 1990s and the end of the dry period, as mangrove growth is favored by the relative salinity reduction. Finally, one of the inverse estuary behavior factors is the low fresh water incoming from the continent. The small area of the Casamance and Saloum basins (20,150 and 26,500 km², respectively) is to be compared with the basins of their two main neighbor basins, the Gambia River and the Senegal River, which provide significant fresh water discharge to their estuary.
- Published
- 2020