Présentations Colloques

Oral Presentation
8.04
Session 8.04: Isotopic and residence time tracers
Koh Eun-hee
Evaluation of groundwater ages in a layered aquifer system using analytical and numerical models
Groundwater age can provide valuable information related to flow mechanism, migration of solute and aquifer vulnerability to contamination. Generally, water pumped at a grounwater well is a mixture of different ages of water particles not having a single age component. To avoid misinterperetation of the groundwater age derived from environmental tracers, it is important to consider mixing and dispersion processes occuring in the aquifer system. In this study, we estimated groundwater ages from 3H-3He environmental tracer data with application of analytical and numerical models to account for the groundwater mixing process.Tritium (3H) and noble gas dissolved in groundwater were sampled in two aquifer systems (shallow perched and deep regional aquifers) of the Gosan agricultural area, Jeju volcanic island. From the interpretation of environmental tracers, the apparent 3H-3He ages for the perched groundwater showed younger ages as 4.4 ~ 11.3 years than that of the regional groundwater, which has ranges of 22.1 ~ >60.0 years. Lumped parameter model estimated that dispersion mixing occurred for the perched aquifer and binary mixing between young perched groundwater and old regional groundwater can be explained for the age of regional groundwater contaminated by nitrate. Regional scaled numerical modeling of groundwater age showed that the importance of full age distributions for better characterizing the nitrate contamination in the complex aquifer system. Our combined evaluation of the analytical and numerical approaches was useful to delineate the dynamics on water and solute mixing in groundwater of the study area.
Republic of Korea