MODEL BUILDING UNIT FOR RAINFALL-RUNOFF SIMULATION

Abstract

This paper investigates the appropriate lumping scale for rainfall-runoff models. Since the location of rainfall inside the lumping scale cannot be reflected to the simulations, it is important to identify the scale in which the spatial variability of rainfall does not affect significantly to the discharge at the outlet. It defines Model Building Unit (MBU) as a maximum catchment size in which explicit consideration of rainfall location is not required for flood predictions. The simulation results in the Yodo River basin showed that MBU is restricted mainly by river channel effects and quantified as absolute size if the catchment size is between 150 km² and 1500 km². MBU is 200 km² for 5 % of allowable relative peak discharge error.