Abstract
In case that interception evaporation and transpiration of forested watersheds can not be directly observed, a method of separately estimating annual interception evaporation and transpiration is studied and proposed. The 365 days in a year are mainly divided into two groups: rainy days having interception evaporation and non-rainy clays having transpiration. Then daily interception evaporation is calculated from rainfall and potential evaporation determined by the temperature, and effect of annual change of forest condition is also considered. Three parameters of the method are determined by using observed multi-year data of precipitation, runoff and temperature in four watersheds in Japan, giving acceptable results of annual evapotranspiration. Finally the changing patterns of interception evaporation and evapotranspiration are analyzed, demonstrating the sensitivity to rainfall and forest change. This method is applicable to the separation of interception and transpiration from the whole evapotranspiration.
