Preliminary study of water origin in the Uspallata valley and its contribution to the Mendoza river with isotopic and hydrochemical techniques. Mendoza, Argentina

Abstract

The Uspallata Valley is located in Mendoza Province (Argentina), at an average altitude of 1,900 m asl. With a north-south direction and a length of around 20 km, it is an intermountain valley placed between the Pre-cordillera (to the east) and the Frontal Cordillera (to the west). The valley discharges to the Mendoza River, the main Andean course that irrigates the largest socio-productive oasis in Mendoza Province. For the last 20 years there has been a significant increase in urban growth and a disordered development of agricultural, touristic, and real estate activities in the southern part of the valley. The objective of this study is to use isotopic and hydrochemical techniques to develop a geohydrological conceptual model, in order to contribute to decision making processes of the provincial management that deals with water and land-use planning. Hydrochemical and isotopic techniques have been used to understand groundwater characteristics and provenance along the valley. Beyond compiling the scarce previous existing data, two monitoring surveys were carried out where physical-chemical parameters and stable isotopes were measured in 39 sites (wells, springs, creeks, and the Mendoza River). The preliminary isotopic balances performed suggest that around 70% of the groundwater comes from the Cordillera Frontal. Moreover, the integrated analysis of new data and existing geological and geoelectric information has allowed the development of a preliminary conceptual model identifying three zones relating to the origin of the water along the Frontal Cordillera. The study is part of the project “Use of isotopic techniques for improving the management of groundwater resources” ARG/7/008, which is funded by the International Atomic Energy.