Date Received: 29-05-2025 / Date Accepted: 14-08-2025 / Date Published: 28-08-2025
This study evaluated projected changes in precipitation, streamflow, and flooding in the Pho Day River Basin by the end of the 21st century under the high-emission scenario SSP5-8.5. An integrated modeling approach combining the Weather Research and Forecasting (WRF) model and the Rainfall-Runoff Inundation (RRI) model was employed, using observational data from 56 meteorological stations, JRA-25/JCDAS reanalysis data, and climate projections from the CMIP6 GCMs EC-Earth3 and HadGEM3-GC31-MM. Validation results showed that WRF accurately captured meteorological conditions for the 2003-2022 period, while RRI reliably simulated the 2019 flood event, confirming the models’ suitability for hydrometeorological assessments. The findings revealed a significant increase in summer (JJA) precipitation by 2080-2099, particularly in the northern and northeastern upstream regions. This leads to pronounced increases in streamflow and flood peaks, especially in downstream areas, resulting in more severe flooding characterized by greater depth and spatial extent,most notably under extreme climate scenarios. Streamflow during the rainy season may rise by 8.8% to 15.6%, with peak flood depths increasing by 1-3 meters. These increases are concentrated toward the end of the wet season, underscoring the considerable impact of climate change on future flood risks.
