Abstract
Climatic variations caused by the excessive emission of greenhouse gases are likely to change the patterns of precipitation, runoff processes, and water storage of river basins. Various studies have been conducted based on precipitation outputs of the global scale climatic models under different emission scenarios. However, there is a limitation in regional- and local-scale hydrological analysis on extreme floods with the combined application of high-resolution atmospheric general circulation models’ (AGCM) outputs and physically-based hydrological models (PBHM). This study has taken an effort to overcome that limitation in hydrological analysis. The present and future precipitation, river runoff, and inundation distributions for the Lower Mekong Basin (LMB) were analyzed to understand hydrological changes in the LMB under the RCP8.5 scenario. The downstream area beyond the Kratie gauging station, located in the Cambodia and Vietnam flood plains was considered as the LMB in this study. The bias-corrected precipitation outputs of the Japan Meteorological Research Institute atmospheric general circulation model (MRI-AGCM3.2S) with 20 km horizontal resolution were utilized as the precipitation inputs for basin-scale hydrological simulations. The present climate (1979–2003) was represented by the AMIP-type simulations while the future (2075–2099) climatic conditions were obtained based on the RCP8.5 greenhouse gas scenario. The entire hydrological system of the Mekong basin was modelled by the block-wise TOPMODEL (BTOP) hydrological model with 20 km resolution, while the LMB area was modelled by the rainfall-runoff-inundation (RRI) model with 2 km resolution, specifically to analyze floods under the aforementioned climatic conditions. The comparison of present and future river runoffs, inundation distributions and inundation volume changes were the outcomes of the study, which can be supportive information for the LMB flood management, water policy, and water resources development.
Highlights
Reports published by the Intergovernmental Panel on Climate Change (IPCC) [1,2] have mentioned that the intensity and frequency of heavy precipitation will increase in the future due Hydrology 2017, 4, 55; doi:10.3390/hydrology4040055
The impact of climate change on hydrological features in the Lower Mekong Basin (LMB) in the cross-boundary region of Cambodia and Vietnam was analyzed by feeding MRI-AGCM3.2S precipitations projected for the present and the future into two distributed hydrological models
The results indicate a significant increase in flood severity in the LMB, predicting extreme floods possibly disastrous to the paddy cultivation in the Mekong Delta (MD) area, which accounts for more than 50% of the rice production in Vietnam [68]
Summary
Reports published by the Intergovernmental Panel on Climate Change (IPCC) [1,2] have mentioned that the intensity and frequency of heavy precipitation will increase in the future due Hydrology 2017, 4, 55; doi:10.3390/hydrology4040055 www.mdpi.com/journal/hydrologyHydrology 2017, 4, 55 to climate change. The projections given by the IPCC reports were based on simulation results from several general circulation models (GCMs), and many studies have assessed changes in hydrological characteristics due to climate change by using those GCM outputs. Quantitative and qualitative assessments of changes in flood characteristics under climate change in river basins are critically important, and are strongly requested by policy-makers, river engineers, and flood fighters for practical river basin management against increasing flood risk. In this context, a study of future extreme flood events is essential. Understanding of future rainfall and river discharge variations, trends, and volumes is essential, considering the impacts on river basins from extreme floods, long-lasting droughts, water storage, and other events due to climate change
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