A univariate Climate Response Function approach for evaluating structural adaptive strategies in the Dongjin River Basin

Global warming and shifting precipitation patterns are intensifying water scarcity worldwide, exposing the limits of current water infrastructure. This study applies a univariate Climate Response Function (CRF) to quantify how climate change affects water supply reliability in a large-scale network linking the Seomjin, Yeongsan, and Dongjin River Basins. It also examines how structural strategies-such as upsizing small reservoirs and inter-basin water transfers-may mitigate reliability declines, using CRFs of the wetness index (the ratio of precipitation to potential evapotranspiration). After simulating natural streamflow with the GR6J model for 31 basins and optimizing water allocation, the relationship between water supply reliability and climate stress was captured by the univariate CRF, and future reliability was projected using CMIP6 climate scenarios. Results show an exponential decline in reliability for the Dongjin River Basin below a wetness index of 1.2 under current management. Even with expanded reservoirs and inter-basin transfers, the CRF did not shift significantly, and minimal shortages were observed under 1991-2020 conditions. Although 2021-2050 projections vary, 2051-2080 forecasts indicate a higher probability of drying, suggesting potential reliability losses. By employing a univariate CRF, this study provides a clear assessment of climate vulnerabilities and highlights the importance of maintaining existing reservoirs and transfer networks to ensure future water supply security.