Because of the traditional medium-and long-term prediction method used to select parameters without reasonable basis when modeling, and the slow convergence speed,complex structure and parameter optimization process of the models we commonly used, an stochastic medium-and long-term prediction method was put forward based on WA and GRNN.The main idea of this model was as follows:First,the multi-time scale characters of hydrologic time series were analyzed with WA method.Then GRNN was used to predict the deterministic component and periodic component, respectively. Finally the two components were stacked as final prediction results. The proposed method was used to predict the data of annual runoff series for Tuojiang River.The results showed that the model was of higher accuracy and better qualified rate than traditional prediction models which indicated the validity and applicability for analyzing and modeling hydrological series.
