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1998
- handle: 10670/1.h1ys1e
- 0303-7495
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Bulletin de l'Institut français d'études andines
Mots-clés
Multidisciplinarias (Ciencias Sociales)Sujets proches
Underground water Subterranean water Ground water Water, UndergroundCiter ce document
Francis Sondag et al., « Existe-t-il une mémoire des 15 000 dernières années dans l'aquifère de l'Altiplano? », Bulletin de l'Institut français d'études andines, ID : 10670/1.h1ys1e
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Résumé
"The aquifer of the central Altiplano shows a Cl concentration that increases from 0.5 meq l-1 upstream to 150 meq l-1 downstream. Values of more than 20 meq l-1 may not be explained by the present hydrological conditions. The main outflow process from the aquifer is the evaporation (E) whose regional quantification has been conducted using the relation established for all arid zone areas: E (mm yr-1) = 63 Z-1.5 where Z (m) is the water table depth under soil surface. The aquifer under study may have acquired its high chlorine content during last lacustrine phase of the Tauca (15 Ka BP). Arguments for this hypothesis are: (i) maximum level of the lake (3780 m) higher than present soil elevation in the area, (ii) same order of salinity in the paleolake and in the more saline groundwater, (iii) identical values of Sr isotopic ratio in calcareous deposits from the Tauca and in saline groundwater, (iv) weak molar ratio of Li/Cl in saline groundwater and in the Tauca, (v) modeling of Cl transport consistent with observed spatial evolution of Cl in groundwater. To this scenario, might be superimposed the assumption of a delay for the convective transfer of salt towards south by the coupled effects of accumulation of salt in the unsaturated zone by evaporation from the aquifer during thousand or so years, and of the subsequent return of this salt downwards to the aquifer during some short rainy periods."