Abstract
This study propose an estimation method of the annual changes of monthly actual evapotranspiration (ET) in a meso-scale river basin (100-2, 800km2) by using a complementary relationship equation and Kojima equation, which require meteorological data, Landsat TM data and digital terrain model (DTM). A surface soil moisture index is proposed in order to describe the surface soil moisture as the index of zero to one. This method was applied to the Abashiri and Tokoro River basin in the eastern part of Hokkaido. The influence of some factors, e.g. land cover category, land development, slope direction and air temperature, on the annual ET of the Abashiri River basin was examined. The annual changes of ET and surface soil moisture index in the Tokoro River basin were also estimated.
