Sensitivity analyses of hydrologic and suspended sediment discharge in the abashiri river basin, hokkaido region, Japan

The Soil and Water Assessment Tool (SWAT) was applied to the Abashiri River basin from 2001 to 2007 using a daily time step. After confirming the reproducibility of the model, hydrological sensitivity analyses against monthly river discharge, evapotranspiration (ET), snow water equivalent (SWE), and suspended sediment (SS) load were conducted under various climate change scenarios. The results of calibration and validation indicated that the model provided satisfactory representation of the flow and SS load discharge. In addition, the hydrological sensitivity analyses revealed that the influence of climate change in the basin will be stronger during winter than summer, especially from January to March. Variation analyses revealed that discharge increased drastically under every scenario from January to March, with the exception of a combination of a 20% decrease in precipitation and a 1°C increase in temperature in January. Furthermore, the ET increased greatly in March due to a multiplier effect of natural conditions and temperature increase scenarios. Moreover, although the SWE decreased in almost all cases, it increased in some cases in December, January, and February. Increasing snow melt in response to an early thawing season and/or precipitation during winter resulted in an increase in SS load discharge, especially during February. On an annual basis, the mean SS load decreased in every scenario except for those in which precipitation increased.