Hydrochemical and isotopic composition of periglacial watersheds in Northern Patagonian Andes

Abstract

Mountain periglacial environments are important sites of water storage and distribution to downstream areas. The present study was conducted in the “La Hoya” subwatershed, in the Northern Patagonian Andes. La Hoya is the main water recharge area of the “Los Bandidos” watershed, from which fresh water is used for human consumption. The aim of this work was to study the hydrogeochemical and isotopic composition of this watershed and evaluate the hydrological and ionic contributions from periglacial landforms, accounting for annual water flow hydrodynamics and climatic trends. Meteorological data, spring and stream flows, electrical conductivity, isotopic content, and major ion concentrations of snow, spring, and stream samples were analyzed from December 2020 to November 2021. Snow melting is the main water contribution to the mountain watershed. Part of the snowmelt drains superficially during the melting season and part of it infiltrates into periglacial landforms, where it is provisionally stored as groundwater. Chemical weathering during groundwater-rock interaction is the main process that regulates water chemical composition, dominating the dissolution of CO2(g) and carbonates, which controls the waters to be of the Ca–HCO3 to Ca–Mg–HCO3 facies type of groundwater. The climate tendency for the last sixty years in this area reflects a decrease in precipitation and an increase in temperatures. This climate trend could affect periglacial environments, modifying the chemical and physical processes that take place in them, which could affect the chemical water quality and the hydrological behavior of the watershed. The chemical and hydrological behavior in watersheds for human consumption should be specially monitored for better use of this resource.