Stable isotope signatures of precipitation and implications for groundwater recharge on Jeju volcanic island, South Korea

High-altitude summer rainfall on Jeju Island, South Korea, serves as the dominant source of groundwater recharge, with rapid flow pathways transporting depleted isotopic signatures from northern slopes to coastal areas. This finding emerges from a stable isotope analysis of oxygen (δ¹⁸O) and hydrogen (δ²H) in monthly precipitation and groundwater, revealing distinct seasonal variability linked to monsoon patterns. Northern-slope precipitation exhibited lower δ¹⁸O values and d-excess, mirroring the isotopic signatures found in groundwater, which suggests preferential flow dynamics. The study underscores the critical role of long-term isotope monitoring in understanding and managing groundwater resources on volcanic islands with unique hydrogeological characteristics.

Kim, M.-C., Shin, W.-J., Koh, E.-H., Koh, C.-S., Kim, G.-E., & Lee, K.-S. (2026). Stable isotope signatures of precipitation and implications for groundwater recharge on Jeju volcanic island, South Korea. Journal of Hydrology: Regional Studies, 64, 103141. https://doi.org/10.1016/j.ejrh.2026.103141