Study On Mid And Long Term Forecast Of Runoff In Hexi Corridor Based On The SCSPG Coupling Model

Hydrological forecast is significant for flood control,drought prevention,and reasonable allocation of water resources,while runoff forecast is among the most critical part.Influenced by geographical factors in Hexi Corridor,climate,human activities and economic development,the runoff data present some complicated features like seasonal fluctuation,mutation and nonlinear characteristics.Therefore,mid and long term forecast of runoff has been a difficult topic at home and abroad.Based on detailed analysis of water resources in Northwest China,this paper focuses on mid and long term trend of runoff in the section of Hexi Corridor in Heihe Basin and Shiyang Basin.According to relevant literature on runoff forecast at home and abroad,this paper finds that there exists disadvantages in past runoff forecast model,such as inaccurate forecast,bad fitting effect and low generalization capacities etc.Therefore,this paper proposes new methods respectively in data preprocessing and construction of forecast model,that is,data preprocessing method,which is based on Seasonal Exponent Adjustment(SEA),Complementary Ensemble Empirical Modal Decomposition(CEEMD),Singular Spectrum Analysis(SSA),and coupling forecast method,based on phase space reconstruction,Particle Swarm Optimization(PSO),Generalized Regression Neural Network(GRNN),called SCSPG model.In addition,in order to illustrate advantages of estimated capacities of the coupling model,this paper puts forward four kinds of comparative models,that is,SCSG,SCPG,SSPG and SPG.Taking Yingluo Gorge Site in Heihe Basin as research subject and selecting the monthly runoff data during 1952-2005 for the study sample,this paper verified the estimated performance of SCSPG coupling model in mid and long term runoff forecast of Yingluo Gorge Site.The results present that,compared with the other four models,the coupling model has lower forecast errors,more accurate explication on data changes and better fitting with actual value.In order to verify the generalization capacities of SCSPG coupling model in different watersheds,this paper takes ZamuTemple Site in Shiyang Basin as research subject,and selects monthly runoff data during 1952-2005 for the research samples as well.The results show that the coupling model has a good estimated performance on runoff forecast in Zamu Temple Site as well,and compared with the other models,its estimated capacities are significantly improved.In empirical analysis in two watersheds,the forecasting accuracy of SCSPG coupling model is about 10%,and the Nash Efficiency Coefficient is above90%,which indicate that the coupling model has a good estimated performance and fitting performance in mid and long term forecast of runoff in Hexi Corridor.