Siriwat Boonwichai creator Shrestha, Sangam Chairperson Babel, Mukand Singh Examination Committee Sutat Weesakul Examination committee Datta, Avishek Examination Committee Royal Thai Government Scholarship Donor AIT Fellowship Scholarship Donor text series technical report th Pathum Thani, Thailand Asian Institute of Technology 2018 continuing eng 1 online resource, 203 leaves : ill. (some col.) Climate change is expected to affect water resources and crop production. The Songkhram River Basin (SRB) in the Northeastern region of Thailand has been identified as vulnerable to climate change due to its low adaptive capacity. This study aims to assess water resources and rice production under future climate scenarios and evaluate the potential of applying adaptation strategies to the water and rice sectors using two approaches: top-down and bottom-up. The former is used to investigate the potential impact of climate change on water resources and rice production, and the latter to understand the current water resources and rice production situations in the basin.Four Regional Circulation Models (RCMs) under two climate change scenarios (RCP4.5 and RCP8.5) were bias corrected using the quantilemapping technique to project the future climate in the SRB for three future periods: the 2030s (2020{u2013}2044), 2055s (2045{u2013}2069), and 2080s (2070{u2013}2094). Multiple RCMs were used to reduce the uncertainty in climate model assumptions. The Soil and Water Assessment Tool (SWAT) model was used to simulate the future streamflow under climate change scenarios. The Decision Support System for Agrotechnology Transfer (DSSAT) model was used to simulate rice growth and yield for the rainfed rice season. The future crop water requirement (CWR), irrigation water requirement (IWR), and crop water productivity (CWP) were also evaluated. A questionnaire survey was conducted to understand the current rice and water situation in SRB. In addition, four adaptation options were evaluated to assess the potential of the rice sector: (i) change in planting date, (ii) change in fertiliser application date, (iii) change in fertiliser application dose, and (iv) supplying irrigation water, as well as a combination of options. The water management of rainfed rice fields was investigated at farm and basin scale. The projection of future climatic conditions shows an increasing trend in both maximum and minimum temperatures. The current annual maximum temperature is 31.7 {u00BA}C (1980{u2013}2004),and average annual maximum temperature is expected to rise up to 32.6, 32.9, and 33.3 {u00BA}C for the 2030s, 2055s, and 2080s under the RCP4.5 scenario, and 32.7, 33.5, and 34.5 {u00BA}C for the 2030s, 2055s, and 2080s under the RCP8.5 scenario. The current annual minimum temperature is 21.5{u00BA}C (1980{u2013}2004), and average annual minimum temperature is expected to rise up to 22.4, 22.9, and 23.2 {u00BA}C for the 2030s, 2055s, and 2080s under the RCP4.5 scenario, and 22.6, 23.5, and 24.6 {u00BA}C for the 2030s, 2055s, and 2080s underthe RCP8.5 scenario. However, future annual rainfall may not change much from the baseline. The current annual rainfall is 1391 mm (1980{u2013}2004). The projected annual rainfall is 1394, 1468, and 1468 mm for the 2030s, 2055s, and 2080s under the RCP4.5 scenario, and 1459, 1451, and 1447 mm for the 2030s, 2055s, and 2080s under the RCP8.5 scenario. The rainfall pattern may change in the future, with higher rainfall in the first half of the year and lower in the second half under both scenarios. Results from the hydrological model (SWAT model) reflected negligible change in average annual streamflow, but seasonal streamflow was found to increase from April{u2013}June and decrease from July{u2013}November under both future climate scenarios. The study also found that changes in rainfall have a greater significant influence on rice yield than temperature, possibly increasing water stress in the future. Temperature rises could increase crop water usage such that the water supplied by higher rainfall alone may not be sufficient. IWR is thus expected to increase in the future. Rainfed rice yield may reduce by 22% under RCP4.5 scenario, and 24% under RCP8.5 scenario by the 2080s. Due to the increment of crop water use and decrease in rice yield, CWP could reduce by 28% under the RCP4.5 scenario, and 26% under the RCP8.5 scenario by the 2080s.Farmer perceptions of climate change and its impact on water and rice sectors in the SRB were assessed by using a questionnaire survey tool. Farmers perceived a changing climate in the SRB. The basin is getting warmer and the rainfall pattern is changing. Although change in climate would bring a negative impact to rice growth and yield, farmers could turn this crisis into an opportunity. Farmers can cope with this issue by combining their experience with suggestions from experts on how to obtain higher rice yield. The current adaptation strategies in the SRB include supply water (pumping from river, pond, and groundwater), alternative wetting and drying (AWD), changing rice variety, changing planting date, and changing the fertiliser application date and dose.Adaptation strategies are required for reducing the impact of climate change on future water availability and rice production. Evaluation of individual adaptation options suggests that supplying 60 mm and 70 mm of irrigation water under RCP4.5 and RCP8.5 scenarios, respectively is the best option for increasing future rice yield. Changing the fertiliser application date and planting date can increase future rice production by 6 and 2%, respectively. Adjusting the fertiliser application dose may reduce future rice production. These results demonstrate that increasing the supply of irrigation water can bring rainfed rice production to its potential yield under future climate conditions. A combination of adaptation options can potentially reduce the impact of climate change on rice fields and increase yields. The study also found that the future water availability is sufficient to meet the rice water deficit. The pond capacity (600 m3) is enough to store water for one ha of paddy field to meet the potential rice yield in rainfed rice season. A reservoir (60 MCMcapacity) may be required for supplying water to the 878 km2area of rice fields in sub-basin 15. However, the feasibility of adaptation strategies would depend largely on available resources and the mindset of farmers. The results of this study are helpful to policymakers in understanding the potential impact of climate change, and the application of adaptation strategies for water and rice sectors in the basin. A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Water Engineering and Management, School of Engineering and Technology Thesis (Ph. D.) - Asian Institute of Technology, 2018 Climatic changes Water-supply Thailand Songkhram River Basin Asian Institute of Technology. http://203.159.5.9/ait-thesis/detail.php?q=B00913 http://203.159.5.9/ait-thesis/detail.php?q=B00913 200324 20260817163654.0