Water resources in Northern Thailand have been less explored with regard to the impact on hydrology that the future climate would have. For this study, three regional climate models (RCMs) from the Coordinated Regional Downscaling Experiment (CORDEX) of Coupled Model Intercomparison Project 5 (CMIP5) were used to project future climate of the upper Nan River basin. Future climate data of ACCESS_CCAM, MPI_ESM_CCAM, and CNRM_CCAM under Representation Concentration Pathways RCP4.5 and RCP8.5 were bias-corrected by the linear scaling method and subsequently drove the Hydrological Engineering Center-Hydrological Modeling System (HEC-HMS) to simulate future streamflow. This study compared baseline (1988–2005) climate and streamflow values with future time scales during 2020–2039 (2030s), 2040–2069 (2050s), and 2070–2099 (2080s). The upper Nan River basin will become warmer in future with highest increases in the maximum temperature of 3.8°C/year for MPI_ESM and minimum temperature of 3.6°C/year for ACCESS_CCAM under RCP8.5 during 2080s. The magnitude of changes and directions in mean monthly precipitation varies, with the highest increase of 109 mm for ACESSS_CCAM under RCP 4.5 in September and highest decrease of 77 mm in July for CNRM, during 2080s. Average of RCM combinations shows that decreases will be in ranges of −5.5 to −48.9% for annual flows, −31 to −47% for rainy season flows, and −47 to −67% for winter season flows. Increases in summer seasonal flows will be between 14 and 58%. Projection of future temperature levels indicates that higher increases will be during the latter part of the 20^th century, and in general, the increases in the minimum temperature will be higher than those in the maximum temperature. The results of this study will be useful for river basin planners and government agencies to develop sustainable water management strategies and adaptation options to offset negative impacts of future changes in climate. In addition, the results will also be valuable for agriculturists and hydropower planners.

中文翻译：

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泰国北部南江上游河流的未来气候及其对水流的潜在影响评估

关于未来气候可能对水文造成的影响，泰国北部的水资源研究较少。在本研究中，使用了耦合模型比较项目5（CMIP5）的协调区域缩小实验（CORDEX）中的三个区域气候模型（RCM）来预测南流域上游的未来气候。使用线性缩放方法对代表性浓度路径RCP4.5和RCP8.5下的ACCESS_CCAM，MPI_ESM_CCAM和CNRM_CCAM的未来气候数据进行了偏差校正，随后驱动了水文工程中心-水力建模系统（HEC-HMS）来模拟未来的流量。这项研究将基线（1988–2005）的气候和流量值与2020–2039（2030s），2040–2069（2050s）和2070–2099（2080s）的未来时间尺度进行了比较。在2080年代，MPI_ESM的最高温度最高为3.8°C /年，ACCESS_CCAM的最低温度为3.6°C /年，在未来最高温度下，未来将变得更暖和。平均月降水量的变化和方向变化很大，在2080年代，RCS 4.5下的9月ACESSS_CCAM的最大增幅为109 mm，CNRM 7月的最大降幅为77 mm。RCM组合的平均值表明，年流量下降幅度为-5.5至-48.9％，雨季流量下降幅度为-31至-47％，冬季流量下降幅度为-47至-67％。夏季季节性流量将增加14％至58％。对未来温度水平的预测表明，在20^个世纪，并且在一般情况下，在最低温度的增加会比在最高温度高。这项研究的结果对于流域规划者和政府机构制定可持续的水管理策略和适应方案以抵消未来气候变化的负面影响将是有用的。此外，结果对于农业学家和水电规划者也将是有价值的。