Assessment of river discharge changes in the Indochina Peninsula region under a changing climate Duong Duc Toan 2014 Assessment of river discharge changes in the Indochina Peninsula region under a changing climate by Duong Duc Toan A dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Philosophy Dept. of Civil and Earth Resources Engineering Kyoto University, Japan 2014 Abstract, Abstract River discharge is a key variable of the hydrological cycle. It integrates all the processes occurring within a river basin (e.g, runoff and_evapotranspiration). Statistical proper of river discharge are seen as an indicator for climate change because they reflect changes in precipitation and evapotranspiration, Thetefore, good ‘estimates offuture river discharge are very important for water resources assessment and water-related disaster management ‘Currently, general circulation models or global climate models (GCMs) are the most promising tools to project future changes and associated impacts in the hydrological eyele.
They have been used to estimate various climatological variables (Eg,„ temperature, precipitation, evaporation, or runoff) which are very important to ‘evaluate the impacts of climate change on hydrology and water resources. Projection of river discharge under climate change is generally taken by driving a hydrological model with outputs from GCMs, In the Indochina Peninsula region, the average surface temperature showed an increase of about 0.0 degree Celsius over the last century according to the latest assessment report of the Intergovernmental Panel on Climate Change (IPCC), ‘The region is likely to suffer more from climate change based on the increasing frequency and intensity of extreme weather events such as floods, droughts, and tropical cyclones. Therefore, an assessment of potential future changes in river discharge in the Indochina Peninsula region isessential Abstract, Thị thesis focuses on projection of river discharge inthe region under a changing climate using flow routing model IK-FRM and runoff generation data from the super-high-resolation atmospheric general circulation model MRI-AGCM3 2S which was jointly developed by Meteorological Research Institute (MRI) and Japan Meteorological Agency (IMA) for three climate experiments: the present timate (1979-2008), the near future climate (2015-2044) and the future climate (2075-2104), “The potential future changes in river discharge in the Indochina Peninsula region ‘were examined by comparing projected river discharge in the near future and future climate experiments to the one in the present climate experiment. The statistical analysis of river discharge changes in the region was cartied out to locate possible hotspot basins with significant changes related to floods, droughts or water resources, “The uncertainties in the future climate projections were also evaluated using different ensemble experiments from MRI-AGCM and MIROCS datasets.
Bias correction of runoff generation data was considered to improve river discharge projection using ‘output ofthe land surface process model SiBUC, ‘The increase of flood risk was found in the Irawaddy River basin (Myanmar) and Red River basin Vietnam), The risk of droughts tended to increase inthe middle part ‘of Mekong River basin (Lao PDR) and in the central and souther part of Vietnam ‘The statistical significance of future changes in river discharge in the Indochina Peninsula region was also detected inthe Irawaddy River basi, the upper most pat of the Salwoen and the Mekong River basin, and in the central pat of Vietnam. In _ulditon, the uncertainty in tết discharge projection arising from the differences in ‘cumulus convection schemes and spatial resolution was found much larger than the Abstract, ‘uncertainty sourced from changing sea surface temperature patterns, Land surface process model SiBUC also showed a good performance in reproducing runoffF generation data. However, further works should be done in bias correction of runoft _generation data to improve river discharge projection. Keywords: river discharge projection, statistical significance, MREAGCM3 2S, IK: FRM, bias correction.
Acknowledgements Declaration of authorship 1 declare that this thesis and the work presented in it are my own and have been ‘generated by me as the result of my own original research with the exception of any work of others which has all been appropriate referenced. It has not b 1 submitted, cither in part or whole, fora degree at this or any other university. Acknowledgements ‘This thesis was completed in the Laboratory of Hydrology and Water Resources Research, Department of Civil and Earth Resources Engineering, Graduate School of Kyoto University under a full-time PhD course with the guidance of Prof. Yasuto Tachikawa, It has been more improved thanks to the comments and suggestions from examination committee members, Prof.
Fiichi Nakakita and Assoc. Sunmin Kim 1 would like to express my sincere gratitude to my supervisor, Prof. Yasuto Tachikawa, for his immense Knowledge, excellent guidance, and valuable suggestions throughout this research work. I would have never been able to accomplish my thesis without his kind supervision, support, and encouragement, Iwould like to acknowledge Prof.
Michiharu Shiiba, Assist. Kazuaki Yorozu, ‘Assoc. Prof, Sunmin Kim, and other professors in Kyoto University for their valuable guidance, comments, and suggestions to improve my research, Acknowledgements also wish to show my great appreciation to all my family members, especially my parents and my wife, for their endless support and encouragement. 1 would like to say thanks to Water Resources University and Ministry of Education and Training of Vietnam for giving me a chance to take this PhD course at Kyoto University and providing financial support Last but not least, special thanks to all my friends, my colleagues, my lab members ‘and other people who helped me and shared both good time and hard time together during my study in Kyoto University.
Tabieofcontems Table of contents Abstract Ũ Acknowledgements w Table ofcontents vi List of figures. ix List of tables. xi Chapter 1 Introduction 1 1.3 Thesis outline 7 References 9 Chapter2 Study area, input data and hydrological model B 2.1 Study area “ 22 Hydrological model 1s 1 Catchment model Is 2.22 Flow model 0 23 Topographic data 18 2.4 General circulation model data 2 2.1 Atmospheric general cieulation model MRI-AGCM 23 2.42 Mod for intrdiseiplnary research on climate 24 References + Chapter 3 er discharge projection in the Indochina Peninsula region undera ‘changing climate using the MRI-AGCM3.3 Future changes in river discharge in the Indochina Peninsula region under ä ‘changing climate 30 3.1 Changes in water resources.2 Changes in Hood risk 2 3.3 Changes in drought risk: 36 3⁄4. 41 Chapter 4 Statistical analysis of river discharge projected using the MRI- AGCM3.2S dataset in the Indochina Peninsula region, 4B 4.1 Test for normality 4 4.2 Test for statistically significant differences between two means 46 43 Results and discussions.1 Test for normality 48 4.2 Test for statistically significant differences between two means so 44 Conclusions.
35 References 56 Chapter 5 Future changes and uncertainties in river discharge projected using different ensemble experiments of the MRI-AGCM and MIROCS datasets.2 Data and methods 59 45. Results and discussions, ái 5.1 Changes in annual mean discharge ái Tabieofcontems 5.2 Changes in mean of annual maximum daily di charge 65 5.3 Changes in mean of annual minimum daily discharge. B Chapter 6 Bias correction of runoff generation data to improve river discharge projection.2 Methods 79 63 Study area 80 {64 Land surface process model 81 65 Data 2 65.1 Topographic data 2 652, GCM nunoff generation data, 2 6. Meteorological data gã 654 Soil, vegetation, and land use data 86 .5 Resolution and simulation period of SiBUC model 7 {646 Bias correction of GCM runoff generation data, 88 6.7 Results and discussions.1 Reproduction of runoff generation data using SiBUC.2 Bias correction of runoff generation data 93 68 Conclusions.
7 Chapter 7 Conclusion List of ficures List of figures Fig.1 Map of the study area (source: Encyclopedia Britannica, Inc.2 Schematic drawing of a catchment model using a DEM (Arrows in the figure show the flow of discharge on the slope or river unit), 16 Fig.3 River basins in the Indochina Peninsula region provided by the scale-free streamflow network dataset 19 Fig. 24 Example of flow direction data before joining (Arrows indicate flow direction) 20 Fig.5 Flow direction after joining (Shaded grid cells: overlapped grid cells; bold lines: basin divides) a Fig.6 Flow accumulation map ofthe Indochina Peninsula region 12 Fig.1 Ratio of annual mean discharge in the near future climate (a) andin the future climate (b) to the one inthe present climate vi Fig. 32 Ratio of mean of annual maximum daily discharge for the near future climate to the pr ent climate (a), and the future climate to the present climate (b).3 Ratio of standard deviation of annual maximum daily discharge for the near future to the present climate (a), and the future to the present climate (b).4 SLSC values for fitting the GEV distribution to the annual maximum daily discharge for the present (a), the near future (b) and the future climate () 35 ig. 35 Ratio of the 10-year return period annual maximum daily discharge for the near future climate (lft) and the future climate (right) to the present climate.6 Ratio of mean of annual minimum daily discharge for the near future climate to the pres climate (a), and he future climate tothe prese climate ().
37 SLSC values for fiting the Weil I distribution to the annual minimum daily discharge forthe present (a), the near future (b), and the future climate (e). 3/8 Ratio of the 10-year return period minimum daily discharge for the near future to the present climate (a) and the future tothe present climate (b). 39 List of ficures ig, 4.1 W test statistic of annual mean discharge data forthe present climate (lef, the near future climate (middle), and the future climate (right) 49 ig.2 W test statistic of mean of annual maximum daily discharge data for the present climate (left), the near future climate (middle), and the future climate (right) 49 ig.3 W test statistic of mean of annual minimum daily discharge data for the present climate (left), the near future elimate (middle), and the future elimate (right) 49 Fig. 44 Ratio of annual m an discharge for the ne: future climate to the present climate (left), and the future climate to the present climate (right) so Fig.5 Statistical significant differences between annual mean discharge for the near future climate and the present climate (left); and for the future climate and the present climate (righ).
46 Ratio of mean of annual maximum daily discharge for the near future to the present elimate (lft), and the future tothe present climate (right) 2 ig. 47 Statistical significant differences between mean of annual maximum daily discharge for the near future and the present climate (lef); and for the future and the present climate (righ).8 Ratio of mean of annual minimum daily địch: forthe near Future limate 40 the present climate (lef), and the future climate to the present climate (right). 49 Statistical significant differences between mean of annual minimum daily discharge for the near future and the present climate (lef); and the future and the present climate (righ).1 Ratio of annual mean discharge in the future climate experiment to the one pres rt climate experiment “ Fig. 52 Statistical significance differences between annual mean discharge in the ature climate experiment and inthe present climate experiment “ Fig.
53 Ratio of mean of annual maximum daily discharge in the future climate ‘experiment tothe one in the present climate experiment 66 List of ficures ig.4 Statistical significance differences between mean of annual maximum daily discharge in the future climate experiment and inthe present climate experiment. 55 Ratio of mean of annual minimum daily discharge in the future climate to the one in the present climate do Fig, 56 Statistical significance differences between mean of annual minimum daily discharge in the future climate and in the present climate 0 Fig.1 Location of Chikugo River basin (blue) and Oyodo River basin (red) in Kyushu area, Japan sọ ig.2 Schematic image of surface elements in SiBUC model, 81 ig. 63 Disuibudon of collected rain gauge s tation in APHRODITE's Water Resources project (Source: htp:/www.ac jp/precip/productsindex html).4 Schematic representation of quantile-quantile mapping.