| The research area of Dagujia River Basin in is located in Yantai.It is the main source of water supply in the area.It is very important for Yantai,which is relatively short of water resources.Therefore,it is very important to give full play to the unlimited potential of human resources to configure the limited water resources and make the water resources exert the economic,social and ecological benefits in economic,ecological and social development.Since 1950 s,many flood control and water utilizing conservancy projects have been built,which have brought great economic benefits to the society and also changed the natural hydrological situation of the river.It is found that the flow rate varies in varying degrees in different periods.The same rainfall and evaporation amount to different flow values before and after the construction of water conservancy projects.The instability and uncertainty of this data are not conducive to the analysis of the whole long series of rainfall flow relations.We can not get the accurate natural water quantity in this basin,and then affect the actual water resources evaluation and the optimal allocation of water,the comprehensive benefits of water resources-economic and ecological benefits can not be fully excavated,and this kind of change gradually enlarges with the accumulation of water conservancy construction.Therefore,it is very necessary to study the influence of hydrological situation on water conservancy projects and to study the calculation method of natural runoff reduction on the basis of evaluation.This study is based on the study of the reduction calculation of natural runoff in the Dagujia River Basin in Yantai.This study is to explore the reduction calculation of natural runoff year by year.Based on a large number of measured data trend analysis and comparative analysis,the item by term reduction method for traditional water reduction calculation can not fully express the diameter.On the basis of the analysis of the hydrological factors and the influence of water conservancy projects,the PCA-GA-BP model of the reduction calculation of natural runoff based on principal component analysis is established on the basis of the trend of hydrological factors and the analysis of the influence of water conservancy projects.The implicit information in the data is deeply excavated and the nonlinear characteristic is used to improve the calculation precision.The simulation is carried out,and an example is used to verify the application.This study is based on the study of the reduction calculation of natural runoff in the Dagujia River Basin in Yantai.This study is to explore the reduction calculation of natural runoff year by year.Based on a large number of measured data trend analysis and comparative analysis,the item by term reduction method for traditional water reduction calculation can not fully express the characteristics of nonlinear relationship between runoff and influencing factors.On the basis of the analysis of the hydrological factors and the influence of water conservancy projects,the PCA-GA-BP model of the reduction calculation of natural runoff based on principal component analysis is established on the basis of the trend of hydrological factors and the analysis of the influence of water conservancy projects.The implicit information in the data is deeply excavated and the non linear characteristic is used to improve the calculation precision.The simulation is carried out,and an example is used to verify the application.The following steps are mainly carried out:(1)Analysis of the trend of hydrological factorsThis part is a basic study.Through the analysis of the main hydrological factors of the Dagujia River Basin,the change trend and basic law of the rainfall,runoff,evaporation,water level and sediment,the basic situation of the change of water situation in this basin is understood.At the same time,through the comparative analysis and evaluation of the mutual change,it reveals that the river basin is in a long series of different periods.The trend and influence of water regime change lay the foundation for the next part to join the evaluation of water conservancy project construction factors.(2)Analysis of runoff by RVA modelAccording to the situation of water situation and water conservancy project construction in the Dagujia River Basin,the RVA model of the river basin was established,the trend of water situation before and after the construction of water conservancy project was analyzed and discovered,the change degree of water situation under the influence of water conservancy project was quantitatively analyzed,and the main factors affecting the change of water situation were extracted with the analysis of the first part of the hydrological factor.As the main component of the PCA-GA-BP model for water recharge calculation in the Dagujia River Basin.(3)Principal component analysis is used to analyze input samples by dimensionality reduction.According to the analysis of the influence of the water conservancy project on the runoff of the RVA model,eight influencing factors,which are closely related to the natural runoff,are extracted from the two parts of the hydrological factor trend analysis.The influence factors are reduced by the principal component analysis method,and the input samples of the PCA-GA-BP model are determined by the analysis.(4)Optimal weights and thresholds of genetic algorithmWhen the structure of BP neural network is determined,a weight value and threshold are determined initially,the genetic algorithm is used to generate the initial population by coding,and the selection,cross and mutation operators are used to optimize the new weights and thresholds to overcome the slow convergence speed of the BP neural network,which is easy to fall into the local minimum value and then run the model.(5)To structure the PCA-GA-BP model for natural runoff reduction calculation.In the third part,based on the analysis of the main influence factors of principal component analysis in the third part,combined with the optimization of the weights and thresholds of the network model by using the fourth part of the genetic algorithm,the PCA-GA-BP comprehensive model of the water reduction calculation is established in Dagujia River Basin.The error of the method is compared and the applicability of the model is studied.The main research results are as follows:(1)Through the analysis of the trend of five hydrological factors,we find that rainfall,evaporation,water level and sediment are consistent with the runoff.Therefore,through the study of the hydrological trend analysis,four factors such as rainfall,evaporation,water level and sediment can be used as the influencing factors to enter the principal component analysis method.Carry on the main influence factor analysis.(2)Through the analysis of the elements of water conservancy projects,after the factors of water conservancy projects are added to the hydrological factors,before the factors of water conservancy projects are found and without the elements of water conservancy projects,the hydrological factors such as flow and other hydrological factors have a greater impact on the trend,and the urgency of the reduction calculation of the runoff and the necessity of the study are also reflected.(3)Through the RVA method to evaluate the water conservancy project affecting the hydrological situation,we have obtained the hydrologic change degree of 33 hydrological indexes,among which the monthly average flow rate,the maximum flow rate and the minimum flow time change degree of the flood season are low,which indicates that the water conservancy projects have smaller impact on these factors.These three items can be used for nonlinear mapping of natural runoff.So the three factors are added to the principal component analysis.(4)By using the principal component analysis method,the input samples of the model are obtained by optimizing the dimensionality reduction processing factors which are closely related to the variables,and the genetic algorithm is used to optimize the weight threshold to improve the convergence speed and reduce the error.The three algorithms are seamless and build up a PCA-GA-BP model.The PCA-GA-BP model constructed for the natural runoff reduction can well simulate the size of the natural runoff in the Dagujia River Basin,which is more time saving than the traditional successive reduction method,and the error is also within the allowable range.Therefore,only the hydrological indexes-rainfall,measured runoff,maximum flow time and minimum flow time are needed,and the natural runoff of Dagujia River Basin can be obtained through the established model. |
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