Chaiwat Ekkawatpanit, Weerayuth Pratoomchai Department of Civil Engineering King Mongkut’s University of Technology Thonburi, Bangkok, Thailand Naota Hanasaki National Institute for Environmental Studies, Tsukuba, Japan So Kazama Tohoku University, Sendai, Japan November, 2015 Climate Change Impact on Water Resources using Global Climate and Hydrological Model 2015 APEC Typhoon Symposium (APTS) Lessons Learned from Disastrous Typhoons

Outline of presentation  Introduction  Objective of the study  Study area  Methodology  Results and discussion  Conclusions 2

Introduction There is a 95% (IPCC, 2013) consensus among the scientific community that climate change is real and human activity is the main cause (anthropogenic climate change) In fact, there are uneven temporal and spatial distributions of climate change impacts ? 3

Objective This study aim to investigate the impacts of climate change on water resources in the Upper Chao Phraya River Basin in Thailand, which concerned among climatology and river discharge. 4

Study area: The Upper Chao Phraya River basin (UCP)  The basin covers an area of 109,973 km 2 or 22% of the country’s area o 60.0% is forest o 35.6% is agricultural area o 4.4% is classified to other, e.g., urban, water bodies 5

7 climate variables: Methodology (Mathematical models): Kazama et. al CMIP5 - Coupled Model Intercomparison Project Phase 5 5 GCMs under 3 scenarios RCP 2.6 RCP 4.5 RCP 8.5 6

Land Surface Hydrology Module (LSM): Soil water balanceEnergy balance Soil water balance  Energy balance  The model was developed by Hanasaki et al., 2008; 2012;

Schematic of H08’s river module River Module: 8

Reservoir Operations Module: In this study, we focused on Bhumibol and Sirikit Reservoirs only. In reality, reservoir operations are very complex We propose an idealized simple reservoir model. Although simple, this simulation offers good insight into river management and planning. 9

10 Climate change conditions: 5 GCMs used in this study GCMsInstitutions Resolution (lon × lat) OriginalApplied in the study MIROC-ESM-CHEMNational Institute for Env. studies2.81° × 2.81°5.0’ × 5.0’ HadGEM2-ESMet office Hadley centre1.87° × 1.24°5.0’ × 5.0’ GFDL-ESM2MGeophysical fluid dynamics Lab.2.50° × 2.00°5.0’ × 5.0’ IPSL-CM5A-LRInstitute Pierre Simon Laplace3.75° × 1.87°5.0’ × 5.0’ NorESM1-MNorwegian Climate Centre2.50° × 1.87°5.0’ × 5.0’  Used linear interpolation to interpolate the original resolution of GCM data to the study grid size of 5’ x 5’ or about 10 km x 10 km  Shifting and scaling method was used for removing systematic biases of the original GCM data (e.g., Alcamo et al., 2007; Hanasaki et al., 2013)

Results: Model Calibration 11

12 Results: Annual mean air temperature Current period ( ) Projection period ( ) RCP2.6 average from 5 GCMs Change (Future – Current)

Surface Air Temperature change ( ) RCP 2.6 RCP 4.5RCP 8.5 Results: Annual mean air temperature 13

Results: Annual mean air temperature 14 The increasing of surface air temperature in the near future was in a range of which had a as a mean annual surface air temperature.

Results: Surface water balance from the LSM Average annual rainfall, evaporation, and runoff ( ) Rainfall = 987 mm Evaporation = 810 mm or 82% of annual rainfall Surface runoff = 177 mm or 18% of annual rainfall 15

Results: Water balance 16 MIROC and NorESM GCMs showed increasing trend for all variables

Results: Rainfall 17 Current period ( ) Projection period ( ) RCP2.6 average from 5 GCMs Change (Future – Current)

Results: Rainfall 18 RCP 2.6 RCP 4.5 RCP 8.5 Annual Rainfall change There were both increase and decrease in projected rainfall changes except RCP4.5 scenario. This scenario showed that over the whole basin rainfall might be reduced by 20 mm to 50 mm.

19 Result: River discharge at Chiang Mai From January to June, the river discharge projections from the GCMs decreased. In contrast, during the second monsoon period (August to October), river discharges in the upper area (mountainous region) showed significantly increased.

20 Result: River discharge at Kampangphet March to June, river discharge projections of river discharges from the GCMs are decreased. In contrast, during July to February, the river discharges in the downstream showed significantly increased.

21 Result: River discharge at Nakorn Sawan (c) RCP 8.5 River discharge in C.2 quite stable from January to May because this period was controlled by reservoir operations. During the wet season (May to October), the river discharge at the basin outlet station was peak in October but the rainfall was maximum in September.

Conclusions  The increasing of annual surface air temperature in the near future ( ) was in a range of °C, which had a °C as a mean annual surface air temperature.  Maximum air surface temperature is projected to increase by °C in the projected period related to the reference period ( ).  Rainfall tended to decrease in the near future, on average.  For the river discharge projection, Chiang Mai and Kampangphet will increase in the risk of both drought (first monsoon) and flood (second monsoon) but Nakorn Sawan province might predominate by drought. 22

Thank you for your kind attention. 23