Impacts of national adaptation plans on water security under future climate uncertainty: system performance and internal dependency in the Seomjin River Basin

ABSTRACT Four-panel summary diagram showing: (top left) maps of national adaptation plan locations in the Seomjin River Basin, (top right) boxplots of changes in reliability, resilience, and vulnerability across four water-use sectors, (bottom left) choropleth maps of internal dependency under baseline and difference scenarios for each sector, and (bottom right) scatter plots of RRV metrics against internal dependency with LOWESS trend lines. Climate-induced hydrological variability poses increasing challenges to basin-scale water security, highlighting the need to evaluate the effectiveness of climate adaptation strategies under future uncertainty. This study assesses how national adaptation plans influence water security in the Seomjin River Basin using an integrated modelling framework that couples the Soil and Water Assessment Tool and the Water Evaluation and Planning system. Water security is evaluated through system performance indicators, including reliability, resilience, and vulnerability, together with an internal water dependency metric based on the water footprint concept. The results show that adaptation measures improve recovery capacity and reduce localized supply stress, particularly for domestic and industrial water uses. In contrast, agricultural water supply and instream flow remain largely governed by hydrological variability and show limited response to adaptation. The analysis of internal water dependency indicates that the adaptation plans do not substantially alter the basin's structural reliance on internally generated water resources. These findings suggest that current adaptation strategies enhance operational performance but are insufficient to fundamentally strengthen long-term water security under climate uncertainty.