Abstract

The Salar de Atacama is located in the most arid desert in the world. Despite its extreme conditions, it has many ecosystems of high ecological value. The Soncor ecosystem, a sequence of lagoons, is the most important environment of the region as it acts as the centre for the breeding of the Andean Flamingo. This salt flat also contains significant mining deposits and is an important water source for the region. Freshwater and brineenriched in lithium and potassiumare being pumped from the aquifers near to the Soncor ecosystem, which has so far not been greatly affected by this groundwater extraction. However, there is a potential risk that future anthropogenic effects may disturb this fragile environment. The objective of this study is to determine the origin of the water sources of the Soncor ecosystem so as to adequately manage its water resources. Three hypotheses previously proposed in the technical literature were investigated in order to determine proactive actions to protect this fragile ecosystem. The study utilized classic hydrogeological techniques, such as the construction of stratigraphic profiles, piezometric maps and stream gauging, combined with less-common isotopic techniques, such as the Sr-87/Sr-86 ratio. The results confirmed the hypothesis that the origins of the water sources are associated with groundwater inputs coming from the east side of the salt flat, in the north of the basin.Editor Z.W. Kundzewicz; Associate editor M. AcremanCitation Ortiz, C., Aravena, R., Briones, E., Suarez, F., Tore, C., and Munoz, J.F., 2014. Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile. Hydrological Sciences Journal, 59 (2), 336-350. ResumeLe salar d'Atacama est situe dans le desert le plus aride du monde. En depit de ces conditions extremes, il possede des ecosystemes de haute valeur ecologique. C'est le cas du systeme lacustre du Soncor qui est le lieu de nidification du flamand andin le plus important au monde. Ce salar possede aussi d'importantes reserves minerales et constitue une importante ressource en eau pour la region. L'ecosysteme du Soncor est situe a proximite d'aquiferes dont sont extraites, sans trop d'impacts jusqu'a maintenant, d'importantes quantites d'eau douce et de saumures riches en potassium et en lithium. Il existe cependant un risque que cet environnement fragile ne soit affecte par les activites anthropiques futures. La presente etude a pour objectif de determiner l'origine des eaux de l'ecosysteme du Soncor afin de gerer convenablement ses ressources en eau. Les recherches ont porte sur trois hypotheses proposees dans la litterature technique, afin de proposer des actions efficaces pour la protection du systeme. L'etude a mis en OEuvre des methodes hydrogeologiques classiques comme la construction de profils stratigraphiques, la cartographie de la piezometrie et le jaugeage des cours d'eau, et des techniques isotopiques plus innovantes comme l'etude du rapport Sr-87/Sr-86. Les resultats confirment l'hypothese selon laquelle l'origine des eaux du Soncor est associee a des apports d'eau souterraine provenant de la partie orientale du salar, dans la zone Nord du bassin.