Study On The Situation And Variation Characteristics Of Water And Sediment In The Wuding River Basin

In recent years,due to the combined influence of climate change and human activities,the runoff-sediment yield in Wuding river basin changes dramatically,and the runoff and sediment discharge decreased sharply,the time series also shows significant nonlinearity and complexity.In view of the complex hydrological variability in runoff and sediment transport processes,and various types of variation are intertwined and superimposed,making it difficult to recognize the variation law by a single method.Therefore,based on the variation law of runoff-sediment,the identification of variation types of runoff and sediment discharge,and the analysis of the driving factors of runoff-sediment variation,this paper studies and analyzes the variation characteristics of runoff,sediment discharge sequence and runoff-sediment relationship between 10 hydrological stations in Wuding River basin,in order to identify the law and driving reasons of runoff-sediment variation in Wuding river basin.The research content and related results are as follows:(1)Law of runoff-sediment identification Through the analysis of the interannual variation of runoff-sediment in 10 hydrological stations in Wuding river basin,it can be seen that runoff-sediment situation has changed significantly since the 1970 s,and the runoff and sediment discharge of 10 hydrological stations in Wuding river basin have been significantly reduced,and the interannual variations in runoff and sediment transport at each station are large.At the same time,the change of runoff-sediment relationship in Wuding river basin is discussed by the single cumulative curve of runoff and the double cumulative curve of runoff-sediment discharge,which can get the runoff-sediment relationship of each station is basically stable,and there is no systematic deviation.But there are variation points of runoff-sediment relationship in the time domain,which occurs mostly between 1970-1978,the runoff-sediment relationship before and after the variation points presents a stable trend(except the hydrological station of Han jiamao).(2)Testing of variation types of runoff and sediment discharge Taking the measured annual runoff and sediment transport sequence of 10 hydrological stations in Wuding river basin as the research object,integrates the empirical modal decomposition,STARS method and iterative cumulative squared sum(ICSS)method to construct a set of multi-method coupled hydrological variation type testing system.The system tests the trend variation,mean jump variation and variance variation of annual runoff and sediment discharge series at each station.The results show that the variation types of runoff and sediment discharge sequences in 10 hydrological stations in Wuding river basin are different,the types of variation are complex and variable,it covers trend and mean jump double variation,mean jump and variance double variation,trend and variance double variation,and trend,mean jump and variance triple variation types.In addition,a single type of variation occurs in the runoff sequence.This indicates that under the combined influence of climate,underlying surface conditions and human activities,the evolution process of river runoff and sediment transport in Wuding river basin is increasingly complex and tends to develop towards compound variation.(3)Analysis of driving factors of runoff-sediment variation Aiming at the complex variation of runoff and sediment discharge series in Wuding river basin,a driving and analytic method based on runoff and sediment discharge data is proposed,which consists of three decomposition and synthesis sequences of runoff and sediment discharge series at each station,namely Residual sequence,IMFs sequence and stationary IMFs sequence,calculate their correlation with precipitation,evaporation,interception of water quantity of silt dam,storage capacity of reservoir and consumption of agricultural irrigation,the specific physical causes of the variation of the corresponding sequence are judged by combining the actual situation of the basin.The results show that the trend variation of annual sediment transport is driven by silting dam construction and NDVI changes.The mean jump variation is mainly driven by the change of precipitation and silting dam construction.The variance variation is mainly caused by the change of precipitation and NDVI.The trend variation of annual runoff sequence is driven by the change of evaporation,silting dam construction,reservoir construction and water consumption of agricultural irrigation.The mean jump variation is mainly driven by the change of precipitation,reservoir construction and water consumption of agricultural irrigation.The variance variation is mainly caused by the change of precipitation.