Abstract
The origin of waters from small springs located at the hyper-arid northern coast of Chile, in the vicinity of Antofagasta, is discussed after hydrogeochemical and isotopic studies and supported by groundwater flow hydrodynamic considerations. Spring water is brackish to saline, with electrical conductivity ranging from 2 to 25 mS/cm. Chemical and water isotope data (18O and 2H) show that the rainfall events that produced part of the recharge could correspond to wetter conditions than at present. Their origin could be related to the emplacement of warm sea currents facing the coast of northern Chile, possibly associated to incursions of El Niño Southern Oscillation (ENSO). Radiocarbon dating and preliminary groundwater hydraulic calculations indicate that these spring waters could be remnants of a more significant recharge in the Cordillera de la Costa than that produced today during the less arid period about 5,000 to 3,000 years ago. The exception is Las Vertientes spring which is the only one that receives water transferred from the Central Depression. The springs are the visible discharge of a regional groundwater body in the very low permeability Cordillera de la Costa, whose hydraulic conductivity decreases downward and flow is dominantly though fissures and storage in the low porosity rock matrix.
Highlights
IntroductionAlong the coastline of northern Chile, in the Atacama Desert, an extensive mountain range called Cordillera de la Costa (coastal range) exists
Along the coastline of northern Chile, in the Atacama Desert, an extensive mountain range called Cordillera de la Costa exists
The main conclusions are: 1. Coastal springs chemical and isotopic water composition and dissolved sulfate show that water was recharged in the coastal area of northern Chile and not inland, except for Las Vertientes spring, which has a composition characteristic of groundwater in the Central Depression
Summary
Along the coastline of northern Chile, in the Atacama Desert, an extensive mountain range called Cordillera de la Costa (coastal range) exists. It is one of the driest regions of the world, containing areas whose average annual precipitation in many cases is less than 1 mm, which means long periods of extreme aridity and occasional rainfall events widely separated in time. On the western slope of the Cordillera de la Costa some low discharge springs can be recognized. The numerous archaeological sites located in the vicinity of these springs show they are permanent ones (Núñez and Varela, 1968). The small flow is the result of current or past groundwater recharge despite the extreme aridity. The research carried out is to identify the conditions of such recharge
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