Study Of Reservoir Optimal Operation Coupled With ECMWF Ensemble Precipitation Forecasts

Improve the utilization of water resources is one of the important measures to alleviate the water resource crisis. Raising the decision level of reservoir operation is benefit to improve the utilization of water resources, increase the efficiency of electric power generation, and promote the development of the national economy. In the scheduling of reservoir optimal operation, both the unknown runoff and the forecasting uncertainty are the biggest problem. The results of traditional "single " precipitation forecast has the greater uncertainty, so runoff forecast is not accurate enough which leads to the deviations of reservoir operation. In order to take full consideration of the uncertainty of precipitation forecasts, this paper uses ensemble precipitation forecasts information which published by the European Centre for Medium-Range Weather Forecasts (ECMWF) to establish the runoff description model and conduct medium-term runoff forecast. Then establish Huanren Reservoir optimal operation model with the runoff forecast information to research reservoir optimal operation. The primary achievements of this paper include as follows:(1) The ensemble forecast systems of the ECMWF is tested and evaluated by using TS score, BS score and Talagrand distribution, the results show:with the extension of forecast period and the increased of the precipitation’s grade, the accuracy of ensemble precipitation forecasts of ECMWF gradually decreases, but ensemble-mean precipitation forecast results are better than control precipitation forecast; the ensemble members of the short-term precipitation forecast is not divergent enough and there is a system bias of the long-term precipitation forecast.(2) Analysis is taken for the accuracy of ensemble precipitation forecasts, results show: the vacancy rate is greater than the missing rate, and with the extension of forecast period and the increased of the precipitation’s grade, the accuracy rate decreases; the accuracy of no rain forecast is higher, and the accuracy of drizzle and moderate rain forecasts can also be accepted. The ensemble precipitation forecasts information can be applied in runoff prediction model.(3) According to the different characteristics between wet seasons and dry season of the upstream of Huanren reservoir, the paper establishs respectively runoff description model. The5d and10d ensemble precipitation forecasts of ECMWF are used to drive the runoff model. The results show:the simulated effect of5d runoff forecast is good; while t5d runoff forecast appear the phenomenon that the forecasts is biger than the measured runoff. we can see that the forecast effect of ensemble precipitation forecasts information decrease with the extension of forecast period.(4) The runoff forecasts of ensemble precipitation forecasts are respectively applied to optimal operation model of stochastic dynamic programming by the way of control forecast, ensemble-mean and interval. The results show that:using5d ensemble precipitation forecasts can improve the utilization of water resources, increase the economic benefits to hydropower generation; due to the extension of forecast period, the accuracy of ensemble precipitation forecasts reduced,10d ensemble precipitation forecasts cannot be applied directly in Reservoir optimal operation.