Estudio isotópico de los acuíferos de los valles de Tulún y Ullún Zonda, San Juan, Argentina.

ALBERO, M. C.; LEVIN, M.; PANARELLO, H.O.; GARCIA, E.; LOHN, P.

Iaea Technical Document Tecdoc

INTERNATIONAL ATOMIC ENERGY AGENCY

Lugar: Viena, Austria; Año: 1989 vol. 502 p. 11 - 32

1011-4289

Stable isotope and tritium analyses were used to improve knowledge of the origin of groundwater in the Tulum valley, San Juan province, Argentina. Groundwater is mainly recharged by the San Juan river, which originates in the high Cordillera of the Andes, and is consequently depleted in isotopic content. However, this study led to the conclusion that precipitation over the surrounding hills (altitudes between 1500 and 3000 m), which is isotopically more enriched than the San Juan river source, must be taken into account in evaluating the groundwater inventory in different areas of the valley. About 80 wells covering the whole area, especially the piedmont of the hills, were sampled and analysed tostudy the regional influence of the different inputs. The interpretation of the results obtained suggests that the San Juan river has recharged most of the groundwater stored in the valley. Tritium levels provide evidence for the present area of recharge, not only limited to the alluvial fan, but also through the river bed in places where particular structural patterns and permeable deposits permit infiltration. The influence of water from Sierra Chica de Zonda, on the eastern border of the valley, is not significant, at least under present conditions. An important contribution of water from Sierra de Pie de Palo is evidenced in the southeast, i.e. groundwater in this area shows isotopic values that are interpreted as a mixture of water from the San Juan river with samples from the Sierra de Pie de Palo springs.