Insights on the hydrology of southern South America: The value of water stable isotopes

POCA MARÍA; NOSETTO, MARCELO; BALLESTEROS, SILVINA; CASTELLANOS, GEORGE; JOBBÁGY, ESTEBAN

San Luis

Workshop; I Regional Workshop on Isotope Ecohydrology; 2020

IMASL, Grupo de estudios Ambientales

Hosting the flattest sedimentary plains and highest Andean range of the continent, southern South America faces hydrological transformations driven by climate and land use changes. Although water stable isotopes can help understand these transformations, regional synthesis on their composition is lacking. We compiled for the first time a database of H and O isotopic composition for 1659 samples (precipitation, rivers, groundwater and lakes) along latitude (-22.5 to -41.5°), longitude (-55.3 to -71.5°), elevation (1 to 4700 m) and precipitation (~50 to ~1500 mm/yr) gradients encompassing the Chaco-Espinal-Pampas plains, their adjacent Andean Cordillera and smaller mountain ranges. Emerging patterns reveal (i) slight seasonal isotopic trends in precipitation with no effects of event size, (ii) Atlantic/Amazonian vs. Pacific moisture supply to rivers north and south of the ?arid diagonal? of the continent, respectively, (iii) highly uniform isotopic composition in Atlantic/Amazonian-fed rivers vs. poleward isotopic enrichment in Pacific-fed rivers caused by the elevation decline of the Andes, (iv) strong direct evaporation imprint in rivers and shallow (