Abstract: This paper develops a runoff description model using ensemble precipitation forecasts that considers adequately uncertainty in precipitation, and also an optimal operation model of stochastic dynamic programming that maximizes the total power generation of scheduling period under the constraint of firm power. In a case study of the basin upstream to the Huanren reservoir, its optimal operation was calculated by using the ensemble precipitation forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF). Results show an increase of over four percent in power generation, demonstrating the practical value of ensemble precipitation forecasts to scheduling of reservoir operation.