Caracterización Hidrogeoquímica e Isotópica de la Cuenca baja del río Chambo, Provincia de Chimborazo

Abstract

This study presents a Hydrogeochemical and isotopic description of groundwater from the Chambo River Low Basin (CBLB) in the Province of Chimborazo. The purposes of this research were establishing the chemical composition, origin, and groundwater quality, as well as its relationship with aquifers mineralogy. The results were thrown by a study of the physical (pH, temperature, electrical conductivity) and chemical parameters (HCO3-, SO42-, Cl-, NO3-, Ca2+, Mg2+, Na+, K+) of 10 groundwater samples, and the isotopic concentrations of Oxygen 18 and Deuterium from 12 groundwater samples and 42 rainwater samples collected between 2018 and 2019. The basin constitutes the metamorphic rocks of Cordillera Real and volcano-sedimentary rocks of the Interandean Valley. It also presents areas of high infiltration where is filtered the meltwater of the glaciers of the Chimborazo volcano and water from the paramos of Igualata that feed the aquifers in the lower basin. Statistical and graphic observation of the results allowed the identification of four hydrochemical types of water: calcium bicarbonate, sodium bicarbonate, sodium sulfate, potassium sodium sulfate. Considering water circulates through andesitic rocks from volcano-sedimentary Formations, this differentiation was related to a compositional variation of groundwater in the direction of flow reflected by the increase of pH, temperature and ionic content from the recharge zone to the discharge (Chambo River). Finally, the analysis of stable isotopes (Oxygen 18, Deuterium) revealed that groundwater recharge comes from the Chimborazo volcano and has a small contribution from precipitation. Once transported down the basin, it acquires a higher isotopic enrichment due to water-rock interaction, residence time, and groundwater deep.