Transboundary Aquifers and Groundwater Systems of Small Island Developing States: Status and Trends

This report provides a policy-focused summary of the global assessment of transboundary aquifers and groundwater systems in Small Island Developing States. It presents the assessment’s objectives, key messages, selected results, and methodological approach for evaluating groundwater status and trends. The assessment covers 199 transboundary aquifers and 42 groundwater systems in Small Island Developing States, using indicators addressing groundwater quantity, quality, socio-economic conditions, and governance. Data were compiled through a global inventory based on questionnaires and consultations with national experts, supplemented by modelling of current and future conditions for selected transboundary aquifers. The report identifies groundwater stress, pollution, scarcity, saltwater intrusion, human dependence, and governance gaps as important concerns across the assessed systems.