Assessment of the potential changes in low flow projections estimated by Coupled Model Intercomparison Project Phase 5 climate models at monthly and seasonal scales

This study assesses changes in low flow seasonality in response to climate change using Coupled Model Intercomparison Project Phase 5 (CMIP5) climate models. The precipitation‐runoff modelling system (PRMS) model was applied to project future streamflow using 13 global climate models (GCMs) under two emissions scenarios (representative concentration pathway [RCP] 4.5 and RCP8.5). Then, daily projected streamflows for each month in the reference and future periods were used to assess the monthly variation in low flows in Korean river basins. The results showed that high seasonal variation exists in low flows during the wet and dry seasons, including increasing low flows during the dry season and decreasing low flows during the wet season. The low flows are projected to decrease during the wet season by −6.48% in the 2025 period and by −2.59% in the 2085 period under RCP4.5. Under RCP8.5, the low flow is projected to decline in the wet season by −1.72% in 2025 and −4.35% in 2085. However, during the dry season, the low flow is projected to decrease slightly in the 2025 period (−0.49%) but increase significantly in the 2085 period (12.87%) under RCP4.5. Additionally, the low flow is projected to increase in the near future under RCP8.5 (1.87%). The results reveal that under RCP4.5, most Korean river basins are projected to shift from winter low flows to summer low flows. However, under RCP8.5, except for the Han River basin, which is projected to shift from winter low flows to summer low flows, other basins are expected to retain winter low flows. The findings of this study reveal that more consideration of future low flow conditions is needed, and a robust need exists for the preparation of an adaptation plan to ensure a sustainable water supply to prevent severe water shortages during low flows. The results of low flow projections showed that there are high seasonal variabilities for the low flow during the wet and dry seasons. The results revealed under representative concentration pathway (RCP) 4.5 most of the basins are projected to shift from winter low‐flow to summer low‐flow. However, for RCP 8.5, the Han River basin is expected to decrease seasonality ratio and is prone to shift from winter low flow to summer low flow, and other basins are expected to have winter low flow.