River Discharge Projection under Climate Change in the Chao Phraya River Basin, Thailand, Using the MRI-GCM3.1S Dataset

Abstract

The impact of climate change on river flow in the Chao Phraya River basin in Thailand is analyzed by feeding future runoff projection data into a distributed flow routing model. The projection data used consists of daily runoff generation, which is downscaled into hourly data, by assuming the temporal pattern is proportional to GCM generated hourly precipitation. The GCM dataset used is a 20 km spatial resolution general circulation model (MRI-AGCM3.1S) developed by the Meteorological Research Institute, Japan Meteorological Agency, for the present climate experiment (1979-2003), the near future climate experiment (2015-2039), and the future climate experiment (2075-2099). The main findings of the river discharge projections are as follows: 1) clear changes in hourly flood peak discharge, daily drought discharge, and monthly discharge were detected; 2) for each discharge, the degree of change differed by location; 3) the changes appeared in the near future climate experiment and became clearer in the future climate experiment; and 4) a significant decrease in discharge was detected at the Pasak River basin in October.