Abstract
Due to a continuous increase in global temperature, the climate has been changing without sign of alleviation. An increase in the air temperature has caused changes in the hydrologic cycle, which have been followed by several emergencies of natural extreme events around the world. Thailand is one of the countries that has incurred a huge loss in assets and lives from the extreme flood and drought events, especially in the northern part. Therefore, the purpose of this study was to assess the hydrological regime in the Yom and Nan River basins, affected by climate change as well as the possibility of extreme floods and droughts. The hydrological processes of the study areas were generated via the physically-based hydrological model, namely the Soil and Water Assessment Tool (SWAT) model. The projected climate conditions were dependent on the outputs of the Global Climate Models (GCMs) as the Representative Concentration Pathways (RCPs) 2.6 and 8.5 between 2021 and 2095. Results show that the average air temperature, annual rainfall, and annual runoff will be significantly increased in the intermediate future (2046–2070) onwards, especially under RCP 8.5. According to the Flow Duration Curve and return period of peak discharge, there are fluctuating trends in the occurrence of extreme floods and drought events under RCP 2.6 from the future (2021–2045) to the far future (2071–2095). However, under RCP 8.5, the extreme flood and drought events seem to be more severe. The probability of extreme flood remains constant from the reference period to the near future, then rises dramatically in the intermediate and the far future. The intensity of extreme droughts will be increased in the near future and decreased in the intermediate future due to high annual rainfall, then tending to have an upward trend in the far future.
Highlights
The impact of climate change has been apparent around the world with high intensity.Extreme weather events occur more frequently in the warmer and wetter atmosphere than in the past few decades
The maximum Green House Gas (GHG) emission scenario (RCP 8.5) provides a significant increase in air temperatures, while they are slightly raised under the minimum GHG emission scenario (RCP 2.6)
According to the changes in annual rainfall and runoff with the Flow Duration Curve, Return period of peak discharge, and Standardized Precipitation Index, the probability of extreme flood events in the Yom and Nan River basins are insignificant under scenario
Summary
The impact of climate change has been apparent around the world with high intensity.Extreme weather events occur more frequently in the warmer and wetter atmosphere than in the past few decades. More water vapor is added to the atmosphere, due to increasing air temperature, leading to fluctuation in weather circulations [1]. This causes changes in precipitation patterns, which have significant impacts on the hydrologic cycle [2,3], followed by more extreme hydro-climatic events such as floods and droughts [4]. The extreme hydrological events are expected to be more frequent with an extra 1 ◦ C increase in the air temperature [6] because of a shorter precipitation season [7] and an earlier beginning of the snow melting period [8]. Drought events have become more intensified due to strained water resource systems from population growth and changes in climate [9]
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