A hydrogeochemistry and isotopic approach for the assessment of surface water–groundwater dynamics in an arid basin: the Limarí watershed, North-Central Chile

This paper describes the results of a hydrochemistry and isotopic study of surface water and groundwater dynamics at the Limarí River basin, arid North-Central Chile. The study involved two sampling campaigns, performed in April (Fall, at the end of the irrigation season) and December 2010 (late Spring, at the peak of the irrigation season). The main results show the effect of La Paloma and Hurtado dams on the chemical and isotopic compositions of the Grande and Hurtado rivers (main tributaries of the Limarí River), the influence of return flows to the Limarí River from surface water irrigation in agricultural areas, the local effects of metallurgical operations in the El Ingenio Creek, the effect of water–rock interaction processes, and the nearby coastal belt influence on the Punitaqui Creek area and the lower part of the Limarí River. In addition, this study shows an active interaction between surface water and shallow groundwater, and a minor importance of local precipitation events, on the hydrological behavior in the study area. An exception is the Rinconada de Punitaqui zone where the results are consistent with the origin of the water being associated with local precipitation. Also, sources of sulfate, which is present in high levels especially in surface waters, have been assessed. The results of this study, based on an integrated use of chemical and isotopic tracers, provide sound and useful information to establish the level of interaction between surface water and groundwater, allowing the development of a hydrological conceptual model for the area.