Estimate of recharge of a rising water table in semiarid Niger from 3H and 14C modeling |
| |
| Authors: | Favreau Guillaume Leduc Christian Marlin Christelle Dray Martial Taupin Jean-Denis Massault Marc Le GalLaSalleCorinne Babic Milanka |
| |
| Institution: | Institut de Recherche pour le Developpement, UMR HSM, BP 5045, 34032 Montpellier cedex, France;33 (0)4 67 14 90 12;fax 33 (0)4 67 14 47 74;;;Laboratoire d'Hydrologie et de Geochimie Isotopique, Bat. 504, Universite de Paris-Sud, 91405 Orsay cedex, France;Centre de Recherches Geodynamiques, Universite de Paris–6, BP 510, 74203 Thonon, France;IRD-INAMHI, Apartado postal 17.12.857, Quito, Ecuador;School of Earth Sciences, Faculty of Sciences and Engineering, Flinders University of South Australia, GPO Box 2100, Adelaide SA 5001, Australia |
| |
| Abstract: | A hydrodynamic survey carried out in semiarid southwest Niger revealed an increase in the unconfined ground water reserves of approximately 10% over the last 50 years due to the clearing of native vegetation. Isotopic samplings (3H, 18O, 2H for water and 14C, 13C for the dissolved inorganic carbon) were performed on about 3500 km2 of this silty aquifer to characterize recharge. Stable isotope analyses confirmed the indirect recharge process that had already been shown by hydrodynamic surveys and suggested the tracers are exclusively of atmospheric origin. An analytical model that takes into account the long-term rise in the water table was used to interpret 3H and 14C contents in ground water. The natural, preclearing median annual renewal rate (i.e., recharge as a fraction of the saturated aquifer volume) lies between 0.04% and 0.06%. For representative characteristics of the aquifer (30 m of saturated thickness, porosity between 10% and 25%), this implies a recharge of between 1 and 5 mm/year, which is much lower than the estimates of 20 to 50 mm/year for recent years, obtained using hydrological and hydrodynamic methods and the same aquifer parameters. Our study, therefore, reveals that land clearing in semiarid Niger increased ground water recharge by about one order of magnitude. |
| |
| Keywords: | |
| 本文献已被 PubMed 等数据库收录！ |
|
