Studies On Watershed Hydrological Forecast Modeling And Comprehensive Utilization Method Of Reservoirs

In the field of hydrology,hydrological forecasting and modeling has been researched as a hot issue for many years.With the construction of large-scale reservoirs,huge changes of the space and time distribution have taken place.Therefore,it puts forward a new challenge for hydrological forecast model.Flood disaster is one of the biggest natural disaster to human which behaves high frequency and strong force.The destructive effect is more significant in China since many people live around rivers.on the other hand,the construction of reservoirs has brought considerable economic benefits,however,the influence of dam block effect seriously affects the natural rhythm of watershed and triggers a series of serious ecological problems.In this thesis,the main attention is focused on the key scientific problems and technical difficulties of high precision runoff forecasting and joint optimization operation for cascade hydropower stations under the background of high efficiency,stable and safe operation for cascade hydropower stations in the Yangtze river basin in China.The innovation of this thesis can be summarized as follows:(1)Based on the research on modeling principle and parameters calibration method of Xinanjiang,API,and Tank model,the performance limitations and regional characteristics of hydrological forecasting models under different physical background are considered and multi-model coupling methods combining real time correction and combination forecast theory are put forward.A case study in xiangjiaba site shows that the proposed methods can improve the accuracy of hodrological forecasting compared with single hydrological forecasting model.Among the three coupling methods,the effect of overall optimization parameter coupling method is more outstanding than the real time correction-combination forecasting coupling method and combination forecasting-real time correction coupling method.The proposed methods can improve the accuracy of hydrological forecasting effectively.It can be applied to actual hydrologic forecasting.(2)The basic concept,modeling principle and method of system dynamics are expounded in this paper.It helps to understand that the system dynamics method is good at describing the characteristics of multivariable,high-order,multiple loop,strong nonlinear and complex feedback relation.In view of the dynamic characeristics of watershed rainfall and runoff process,the mutual feedback relations between the variables are analyzed and specific differential equations are characterized.This paper proposes a hydrological forecasting modeling method based on simulation of watershed hydrologic dynamic process with the help of system danymics.It obtaines well effect in the case study on Zhexi watershed and shows that an accurate reflection of the complex mechanism of rainfall and runoff process and simulation of dynamic process of rainfall and runoff are demonstrated in the model.(3)System dynamics method is adopted in this paper to analyze the dynamic process of reservoir flood control.Based on the research of mutual feedback relationship among variables in the flood control system of cascade reservoirs,cascade reservoirs flood control scheduling modeling theory and risk analysis method based on the principle of system dynamics are proposed.Through the simulation of flood control scheduling model,the reserve flood control capacity of Xiluodu and Xiangjiaba cascade reservoirs for Yibin city the distribution of floos control capacity between the two reservoirs are researched.Furthermore,the index of exceeding checking water level and safety flow in the downstream flood control point are selected as index for evaluate the safety of operation of reservoirs.Considering the uncertainty of flood forecasting,the simulation of flood control operation under different scene of incoming water is processed to get the value of risk index of researvior flood scheduling considering the uncertainty of flood forecasting.It provides a new idea for reservoir flood control scheduling and risk analysis.(4)In view of geography,charateristics of hydrology and climate as well as the status of habitat,the IHA method is applied to calculate the variation degree of ecological and hydrological index before and after the construction of Gezhouba dam on the Yichang station on the basis of daily runoff history series.Combined with RVA and Mann Kendall trend test methods,the trend of variation degree of ecological and hydrological index is analysed to study the influence of reservoir regulation on hydrological and ecological characteristics of river.In addition,the ecological water requirement of Chinese sturgeon and four major Chinese carps is comprehensive analysed for the quantifing of ecolical goal with the introduction of Vague set similarity measure.Then the multi-objective ecological operation model of multiple reservoirs for aquatic organism resources protection is established.The solution set quantitative describes the competing relationship between water requirement of aquatic organisms and power generation goal.