The purpose of this paper aims to improve the hydrological prediction accuracy of the storaged-based runoff model by introducing the delayed input rainfall sequences.
In this paper, a storaged-based runoff model, in which the LST-Ⅱ model（the Long- and Short Terms Runoff Model Ⅱ）proposed by Kadoya and Nagai is modified, is developed by including the followings: the estimation method of effective rainfall series forming the surface runoff and／or prompt subsurface runoff, and the lag time of these runoff components in the runoff process of river basin. The outline are as follows:
（１）The observed areal mean rainfall sequence is transformed by the delayed function. The function is evaluated from the distribution characteristics of slope length in a basin model and the equation of lag time applied the practical formula for the concentration time.
（２）By introducing the functional structure of rainwater infiltration in the upper tank of LST -Ⅱ model, the effective rainfall sequence concerned in the surface runoff and／or prompt subsurface runoff is automatically in the proposed model named as the Applied LST-Ⅱ model.
（３）The Applied LST-Ⅱ model is identified by modifying the SP method（Standardized Powell Method）proposed by Kadoya and Nagai.
（４）By a flood runoff analysis using the delayed input rainfall sequence as input data to the Applied LST-Ⅱ model, it is showned that the proposed method is expected to apply as a practical use in the Hii River basin of９１１．４km２ and Otonashi River basin of０．２９６km２.