Abstract

© 2019, Instituto Geologico y Minero de Espana. All rights reserved.The Tuyajto Lake is a saline lake located in the Andean Altiplano of northern Chile, at the foot of the volcano of the same name. It is fed by springs located on its eastern and northern boundaries.These springs discharge groundwater from a volcanic aquifer. Arid conditions dominate in the area, with average precipitation less than 200 mm/year. The tritium content in some groundwater samples shows the contribution of modern recharge to the total groundwater flow. Recharge occurs by infiltration of snowmelt in the austral winter months and to a lesser extent by short but intense precipitation events during the summer. The vertical gradients of rainfall isotopic content (δ18O, δ2H) and precipitation points to the recharge zone of the springs being located at the northern area of the lake, above 4,900 m a.s.l. along the slopes of the Tuyajto volcano, whereas recharge to the springs discharging on the eastern area of the lake originates in the adjacent basins of Pampa Colorada and Pampa LasTecas at altitudes between 4,400 and 4,700 m a.s.l. The water of these springs may contain measurable tritium. The chemical composition of groundwater is the result of meteoric water evaporation processes, high temperature water-rock interaction and dissolution of buried old salt flat deposits. The groundwater flow is shallow, due to the presence of a regional low permeability ignimbrite formation that precludes the formation of deep convective groundwater flow cells due to the high density of brines. At a local scale, theTuyajto lake behaves as a flow-through system with respect to the regional groundwater flow. The persistence of the springs is essential for the existence of the brine sheet and maintaining the ecological conditions for the waterfowl.