ASSESSMENT OF FUTURE WATER RESOURCES IN THE TONE RIVER BASIN USING A COMBINED DYNAMICAL-STATISTICAL DOWNSCALING APPROACH

Abstract

Reliable assessment of Climate Change (CC) impacts on water resources of the Tone river basin is critically important due to its key role on Japan's socioeconomic systems. Hence, to increase the confidence level in CC projections, this study performed high-resolution Pseudo Global Warming Downscaling (PGW-DS) experiments on cautiously selected Coupled Ocean-Atmosphere General Circulation Models (CGCMs) outputs. Value added future climate datasets were developed at the basin scale by removing systematic biases from the PGW-DS outputs using gauged precipitations and a validated statistical bias correction method over this basin. Results showed that annual and monthly climatology of precipitation and corresponding discharges will be increased in the future climate, especially during the Baiu and typhoon periods. Flood-prone areas will be extended and peak discharges will be amplified during warming climate. Recurrence analysis revealed that peak discharges will be increased with increasing return periods, however, larger differences exist in rate of increments between a sub-basin outlet and the main basin outlet, indicating that future investigations should be focused at sub-basins including the effects of dams on discharges to quantify the CC impacts in detail.