Drone view of flooding after Hurricane Melissa made landfall in St Elizabeth, Jamaica, on 29 October 2025. (Image: M. A. Cardona/Reuters)
Small island developing States (SIDS) face unique and pressing water-related challenges. Among the most hydrologically vulnerable regions in the world, they face increasing threats to freshwater availability and quality driven by environmental challenges. Their limited area, geographic isolation, and shared constraints - including accelerated hydrological cycles, complex geology and small aquifers - make them highly sensitive to extreme weather events. These characteristics complicate the accurate assessment and sustainable management of water resources.
To address these challenges, the IAEA is launching a research initiative designed to overcome critical data gaps in vulnerability assessments for island environments. While traditional stable isotopes (δ¹⁸O and δ²H) are invaluable for identifying water sources, they are unable to determine on their own how quickly water moves through an aquifer. This limitation hinders a comprehensive understanding of aquifer dynamics, particularly during storm events.
This Coordinated Research Project (CRP) will apply an integrated approach that combines traditional stable isotope tracers with the short-lived radionuclide sulphur-35 (35S). With a half-life of 87.4 days, 35S offers a unique capability to trace very recent hydrological events, enabling researchers to precisely identify recharge timing and assessment of aquifer responses to storm activity.
The IAEA has developed a simplified method for the application of this radioisotope in hydrological studies, though the tracer has yet to be tested in island settings. Its use could potentially lead to significant advancement in the development of adaptive water management strategies for small island States.
Percent of land area where elevation is below 5m. (Image: Sustainable Development Report for Small Island Developing States 2023)
