降雨パターンに対応した出水伝達関数による発電用ダム流入量予測 : 畑薙第一ダムを対象として

Abstract

In order to convert the hydro-energy given by rainfall into electric energy as effectively as possible, this paper proposes a forecasting method of time variation of river flow rate following a rainfall on upper district of a dam. We have investigated the actual flow increases following 26 rainfalls into a dam for a hydro-power plant located the upper district of the Oh-i River in Central Japan. The derived runoff transfer functions are different from each other, of course. These runoff transfer functions are classified into two groups from the view point of the similarity of their impulse response characteristics. The cluster analysis method is used in this data processing. Further investigation reveals that the above-mentioned two groups have close relationship with the duration time of the rainfalls, i. e., the No.1 Group well corresponds to the rainfalls with the duration of less than 35 hours, while the No.2 Group roughly corresponds to those with longer than 35 hours. Taking this fact into account, the authors develop a new method for a better prediction of the river flow rate following a rainfall. It is well predicted by another method whether a coming rainfall will continue for shorter than 35 hours or not. The river flow rate is forecasted by selection of the derived two types of the runoff transfer function corresponding to the rainfall duration period. This method is actually applied to other 14 rainfalls except the abovementioned 26 rainfalls. The results are obtained with less error in most case.