Groundwater Recharge and Subsurface Flow in the Comodoro Rivadavia Area, Chubut Province, Argentina. Isotopic and Hydrochemical Study

Abstract

Groundwater in the Comodoro Rivadavia area was studied using oxygen-18, deuterium, tritium and hydrochemical evolution.

Stable isotopes in the multilayered system of the “pampa” table — lands define mainly an origin in locally melted snow with isotope composi tion significantly different from rain water over the lower eastern zones. Recharge has been defined as direct and autoctonous. Tritium contents suggest rather small recharge in comparison with the large volume stored in the reservoir. In the neighbouring hill zone, where discharge occurs, springs and wells show isotopic evidence of local flow. In the interhill subunit, regional flow shows salinisation and isotopic enrichment as a consequence of transit through marine facies and evaporation. In colluvial sediments groundwater exhibits higher tritium concentration, lower salinity and an isotope enrichment, due to direct infiltration of local surface water. Aloctonous to local recharge ratios can be estimated by the isotopic composition of the mixture.

In the beach ridges, regional flow and artificial recharge of imported waters, carried by an aqueduct, was isotopically evident.