CONICET | Buscador de Institutos y Recursos Humanos

High glacial mountain environments around theworld are important water reservoirsand are extremely sensitive to the effectsof climate change. Considering that climatechange affects snow accumulation andglacial melting, it is essential to understandthe runoff generation andhydrological dynamics in these type of systems. Andeanglaciers have shown aretreating and thinning pattern since the start of the 21st century. Regardingthis, the stable isotopic composition of waters is useful to assess thecontributionsfrom different sources (i.e., glaciers, precipitation, and tributaries'inputs)to rivers. Several Patagonian mountain rivers have Andean glaciers intheirheadwaters, one of which is the Manso River. In this basin, over the last30 years, theVentisquero Negro Glacier (Manso Glacier's regenerated tongue)experienced a rapidthinning and recession that generated a proglacial lake,called Manso proglacial Lake.In this study, topographic effects upon the stableisotopic composition of river waters(δ2H and δ18O) arerecognized, particularly, the altitude effect. The stable isotopecomposition ofthe Manso River varies downstream, evolving to a composition moreenriched inheavy isotopes in the lower basin, likely due to altitude effects andtheprogressive evaporation that mainly occurs in the lakes' surfaces that therivercrosses. Results show that glacial meltwater is the major watercontributor in theupper basin during early fall. In the rest of the basin thestable isotopic compositionof the Manso River is mainly controlled by thelakes' isotopic signatures and is highlyinfluenced by two tributary rivers. Theconcordance between isotopic models andhydrological data demonstrates thatstable isotopes constitute a valuable tool toquantify the contribution of differentwater sources. This has the potential to be particularly useful in areas wheredischarge data is unavailable.

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