ENVIRONMENTAL ISOTOPES IN THE WATER CYCLE IN THE CATCHMENT OF THE QUEQUEN GRANDE RIVER, ARGENTINA

MARTÍNEZ, D. E.; DAPEÑA. C.; BENTANCOUR VARGAS, T; PANARELLO, H.O.; QUIROZ LONDOÑO, M.; MASSONE, H, E.

Advances in Isotope Hydrology and its Role in Sustainable Water Resources Management (IHS-2007)

INTERNATIONAL ATOMIC ENERGY AGENCY

Lugar: Viena, Austria; Año: 2007; p. 381 - 388

Abstract The catchment of the Quequen GrandeRiver, in the Province of Buenos Aires, is about 10,000 km2 occupying an important area in the Pampa Plain, the most important agricultural productive area in Argentina. The area is covered by Upper Cenozoic loess-like sediments forming an unconfined aquifer, and it is drained mainly by the streams. Most important aspects of its hydrology, like groundwater-surface relationship, recharge volume and area, etc., remain unknown at present. Moreover, before the starting of an IAEA CRP in November of 2004, no isotopic data existed in the catchment.  After about two years of data collecting some results are able to be communicated. Local meteoric water lines has been obtained for three sampling sites in the catchment, presenting clear differences between coastal an inland rainfalls. A clear difference has been stated between the isotopic composition of inland precipitation and the isotopic composition of coastal precipitation. This observation is partially due to continental effect, but different precipitation sources can also be recognized. Preliminarily, the dominance of a recharge area in groundwater composition has been established. Stable isotope composition of groundwater is very homogeneous, corresponding to a well mixed system. The surface water composition is clearly dominated by groundwater discharge, with some evaporation effect, and some temporary changes related to strong rainfall even.