Abstract
In the irrigation systems of Japan, the water demand is usually supplied by the river flow caused by tributary inflow and any shortage is offset by dam release. In this case, excess water is generated easily due to the decrease of water demand in the command area and the increase of river flow by unexpected rainfall. Generally, such excess water is invalidly discharged by the water intake facility such as head work. In this study. we propose the construction of a mid-storage reservoir between the dam and the water intake facility, so that excess water is temporarily stored by such a reservoir. Also, we propose an effective operation method of the dam and the mid-storage reservoir for using the excess water effectively. In this operation, it is necessary to predict the river flow at the water intake facility when dam release arrives there. Therefore, we use the simple prediction model of river flow in order to determine the dam discharge. Furthermore, the operation method is applied to the actual irrigation system whose water use is limited due to water shortage, and the effect is examined by using a simulation method. From this result, the effect of the mid-storage reservoir was clarified quantitatively in drought years by applying the method we suggested.
