The present study attempts to estimate watershed-scale storage changes and storage capacity only from hourly runoff data in Japanese mountainous watersheds, based on a methodology developed by Kirchner in 2009. The results showed that the methodology is applicable even in Japanese mountainous watersheds if we can assume that the rainfall-runoff processes of a watershed could be modeled by a simple storage function. We found this methodology is potentially useful for estimating storage capacity of a watershed from the annual maximum runoff and the minimum runoff. Finally, we suggested a ratio between the annual maximum runoff and the estimated storage capacity multiplied by a runoff record interval as "storage-runoff index" that could be potentially useful for watershed classifications.
