Assessing the Potential Impact of Climate Variability on the Hydrology in the Shubuto River Basin, Hokkaido, Japan

Thursday, 18 December 2014
Asif Mumtaz Bhatti, Toshio Koike and Maheswor Shrestha, The University of Tokyo, Tokyo, Japan
The present research deal with a basin-scale hydrological modeling approach for climate change impact assessment in the Shubuto River basin, Hokkaido, Japan by employing Water and Energy Budget - based Distributed Hydrological Model with improved snow physics (WEB-DHM-S) coupled with AOGCMs output. The WEB-DHM-S provided reliable estimation of seasonal and inter-annual variability of the snow cover area (SCA) and snow depth and the subsequent river discharge production. Comparison of simulated snow cover with the MODIS eight-day snow cover product showed that the distribution of snow over the basin was well captured. The observed and simulated discharge was found to be in well agreement. Sensitivity analysis showed that with the increase in temperature, the fraction of precipitation that occur as snow will decrease, resulting in less snowmelt driven runoff. To elucidate the potential impact of climate variability on the hydrology, WEB-DHM-S was fed with statistically downscaled climate data from the four selected AOGCMs for SRESA1B scenario. The 20 years daily discharge and snow water equivalent (SWE) of all the AOGCMs for the past (1981-2000) and future (2046-2065) have shown uniform direction of trends with decrease in snowmelt induced runoff. Based on the analysis, the mean annual basin wide SWE will decrease, on average 36%, relative to the past. Discharge projections indicated the seasonal march of snowmelt runoff in the future with predicted peak flow to be occurred earlier, on average 14 days, with reference to the past. The findings of present research reinforce the need of improved understanding and representation of changes occurring in the mountain hydrology.