Reference : Application of isotopic tracers as a tool for understanding hydrodynamic behavior of ...
Scientific journals : Article
Engineering, computing & technology : Geological, petroleum & mining engineering
http://hdl.handle.net/2268/164499
Application of isotopic tracers as a tool for understanding hydrodynamic behavior of the highly exploited Diass aquifer system (Senegal)
English
Madioune, Diakher Hélène [Cheikh Anta DIOP University Dakar, Senegal > Department of Geology > > >]
Faye, Serigne [Cheikh Anta DIOP University Dakar, Senegal > Department of Geology > > >]
Orban, Philippe mailto [Université de Liège - ULiège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement >]
Brouyère, Serge mailto [Université de Liège - ULiège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement >]
Dassargues, Alain mailto [Université de Liège - ULiège > Département ArGEnCo > Hydrogéologie & Géologie de l'environnement >]
Mudry, Jacques [Université de Franche-Comté, Besançon > Chrono-Environment UMR 6249 > > >]
Stumpp, Christine [German Research Centre for Environmental Health (GmbH) > Helmholtz Zentrum München > Institute of Groundwater Ecology > >]
Maloszewski, Piotr [German Research Centre for Environmental Health (GmbH) > Helmholtz Zentrum München > Institute of Groundwater Ecology > >]
16-Apr-2014
Journal of Hydrology
Elsevier Science
511
443-459
Yes (verified by ORBi)
International
0022-1694
[en] groundwater ; Environmental isotopes ; Recharge ; Maastrichtian ; Diass horst
[en] The Diass horst aquifer system located 50 km east of Dakar (Senegal) is exploited in two main aquifers covered by a sandy superficial aquifer: the confined/unconfined Palaeocene karstic limestone and the confined Maastrichtian sandstone aquifer underneath. This system has experienced intensive groundwater abstraction during the last 50 years to supply increasing water demand, agricultural and industrial needs. The high abstraction rate from 1989 to 2009 (about 109,000 m3/d) has caused a continuous groundwater level decline (up to 30 m), a modification of the groundwater flow and salinization in parts of the aquifers. The objective of the study is to improve our understanding of the system functioning with regards to high pumping, identify the geochemical reactions that take place in the system, infer origin and timing of recharge by using mainly stable (δ18O, δ2H, 13C) and radioactive (3H and 14C) isotopes.
Water types defined in the Piper diagram vary in order of abundance from Ca–HCO3 (65%), Ca/Na–Cl (20%), Na–HCO3 (3%) and Na–Cl (12%). Values of δ18O and δ2H for the superficial aquifer range between −5.8 and −4.2‰ and between −42 and −31‰, respectively. For the Palaeocene aquifer they range from −5.8 to −5.0‰ and from −38 to −31‰, respectively; values in the Maastrichtian aquifer are between −5.9 and −4.3‰ for δ18O and −38 to −26‰ for δ2H. Plotted against the conventional δ18O vs δ2H diagram, data from the upper aquifer exhibit a dispersed distribution with respect to isotopic fractionation while those of the Palaeocene and Maastrichtian aquifers are aligned parallel and slightly below/or on the Global Meteoric Water Line (GMWL) evidencing ancient waters which had evaporated during infiltration.
The low tritium (generally <0.7 TU) and 14C (0.7–57.2 pmc) contents indicate predominance of older water being recharged during the Pleistocene and Holocene periods. However, few boreholes which exhibit high tritium (1.2–4.3 TU) and 14C (65.7–70.8 pmc) values indicate some mixture with recent water likely through faulting and vertical drainage from the upper to deeper aquifers as well as lateral flow along flow paths to the piezometric depressions created by pumping.
Aquapôle - AQUAPOLE
CTB
Researchers ; Professionals
http://hdl.handle.net/2268/164499
10.1016/j.jhydrol.2014.01.037
http://dx.doi.org/10.1016/j.jhydrol.2014.01.037
The original and final published paper can be found at : http://dx.doi.org/10.1016/j.jhydrol.2014.01.037

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