Climate Change Impact Assessment on Green and Blue Water over Asian Monsoon Region

This study evaluates the climate change impacts on water availability over Asian monsoon region. The water availability is analyzed based on the changes in green water and blue water for the 3 future periods (2020s: 2010 similar to 2039, 2050s: 2040 similar to 2069, and 2080s: 2070 similar to 2099) relative to the reference period (1977 similar to 2006) at each climate zone classified by Koppen climate classification method. To analyze the water availability, a hydrological model was constructed by using the observed climate, hydrological and topographical data (DEM, soil and land use). The water availability was evaluated in terms of green and blue water in all climate zones for the reference period using the observed data and for the future periods using climate change scenarios. The results show that the annual average green water is projected to increase approximately 2.6 similar to 14.6 % for the future period (2080s) in all climate zones and the annual average blue water will increase approximately 9.1 similar to 26.7 % in most of the climate zones except for some Cs and Ds climate zones. However, the monthly average blue water in winter dry zones i.e., Aw, Cw and Cf, will decrease about 2.8 similar to 28.9 % during December to April for 2080s and those at summer dry zones i.e., Cs and Ds, will decrease about 7.1 similar to 30.8 % during March to September for 2080s. On the other hand, the blue water in Am, Aw, Cw, Cf and Dw zones will greatly increase during summer season. These results reveal that the water availability in most of the Asian monsoon region is expected to increase in the future. However, the necessity to manage the water resources in arid regions and to control flood risks in wet regions is inevitable.