Climate Change Impact on Rained Rice Production and Irrigation Water Requirement in Songkhram River Basin, Thailand

Abstract

Songkhram river basin, located in northeast Thailand, is where most of the farmers grow rice in rainy season. The water shortage frequently occurs during dry season as the basin has no dam along the river to store water for agriculture purposes. The river connected with Mekong River. Floods occur in many areas because high rainfall density in the basin and backwater effect from Mekong River. The climate change, temperature rise and uncertainty of rainfall, is significant
influence to water availability for agriculture sector as well as agriculture production especially rice production. The study assesses the impact of climate change on irrigation water requirement (IWR) and rice production for KDML 105 rice variety in wet season (July – November) using DSSAT crop simulation model. The predicted of IWR and rice production were used an ensemble of five Regional Circulation Models (RCMs) under RCP4.5 and RCP8.5 scenarios for three future periods. The results show an increasing trend in both maximum and minimum temperature. The maximum and minimum temperatures are expected to rise up to 1.9 °C relative to baseline period (1980-2004) under RCP8.5 scenario in 2080s (2070–2094). Rainfall may decrease in the first future period, 2030s (2020 – 2044),
and will rise in the 2055s (2045–2069) and 2080s (2070-2094) periods. Rainfall is projected to increase by 13% and 9% relative to baseline period for RCP4.5 and RCP8.5 scenarios respectively in the last future periods (2080s). Therefore, the water shortage might occur in the first period. The middle and last periods might have flood due to higher of rainfall. The trend of IWR is expected to increase, which may rise by 18% and 5% in 2080s under RCP4.5 and RCP8.5 scenario espectively. Due to the increment of temperature and IWR, rainfed rice yield is found to decrease in the future. The rainfed rice yield may reduce by 14% and 10% for RCP4.5 and RCP8.5 scenario respectively in 2080s. However, the IWR is higher due to temperature rise in the future. The increasing of reservoir capacity and improve the water management practices might reduce the crop water deficit and increase crop production.