ESTIMATING FUTURE CHANGES OF EXTREME RIVER DISCHARGE IN THE CHAO PHRAYA RIVER USING d4PDF WITH MULTIPLE BIAS CORRECTIONS

Abstract

 This study constructed a rainfall runoff model corresponding to the characteristics of the Chao Phraya River basin, Thailand and projected future changes of the extreme river discharge in the Chao Phraya River basin with bias-corrected d4PDF rainfall data. As a result, the constructed model well reproduced past several severe flood events; thereby, the probability distribution of annual maximum river discharge at the Nakhon Sawan station between the past experiment in d4PDF and observation was in good agreement at a 4,000 m³/s or more. Future changes of annual maximum peak discharge and flood volume over 2000 m³/s were then projected with three different bias corrections to consider their potential uncertainty. They showed that its change ratio equivalent to a reproduction period of 100 years was 1.55 to 1.63 times for annual maximum peak discharge and 2.23 to 2.27 times for the flood volume, respectively. We could achieve robust impact assessment of climate change on extreme flood with three different bias corrections.