Study On Calculation Method Of Ecological Flow Under The Condition Of Runoff Variation

Water resources maintains human survival and social development.Meanwhile,it plays an important role in ecological.Due to the continuous growth of population and the rapid economic development,the continuous increase in water for industrial and agricultural production and people’s daily use of water has made the supply and demand of water resources increasingly intensified.Excessive water resources development has occupied part of the ecological water volume,and the ecological problems that accompany it have become increasingly apparent.Therefore,in order to comprehensively study the ecological problems of river basin water resources,the effects of hydrological variation should be taken into consideration.Through the analysis of the time characteristics of the runoff series in the Naoli River Basin,there is a further understanding of the characteristics.Analyze the change of ecological flow in the basin and diagnose the ecological health of the basin,provide scientific basis for better use of water resources in the basinThe Naoli River basin is a typical area in Sanjiang Plain in Heilongjiang Province,accounting for more than 25% of the entire Sanjiang Plain.The runoff changes and ecological flow in the Naoli River Basin have significant impact on water resources assessment,agricultural planting structure and environmental changes of Sanjiang Plain.Therefore,this study is based on the runoff and rainfall data from four hydrological stations in the Naoli River Basin.The main research contents are as follows:(1)The Basic Characteristic Analyses of Annual Runoff and Interannual RunoffThe paper tends to analyze the basic characteristics of runoff in the Naoli River Basin through the nonuniform coefficient of distribution within the year,the complete adjustment coefficient during the year,the concentration within the year,the concentration period and the magnitude of change.The analysis results reveal that the wavy degrees of the inter-annual runoff in the Naoli River Basin have gradually increased,which increase the risk of flooding and drought.In addition,both the uneven distribution of runoff and the concentration degree of water resources has increased during the year.Moreover,the generation of runoff is dependent on the flood peaks produced by the concentrated rainfall in the several months,which lead to the decline of the regulation to the inner diameter flow in the basin and go against the full utilization of water resources.By calculating the statistical parameters of precipitation and runoff in the Naoli River basin,the interannual characteristics of the runoff changes are initially analyzed to obtain the regularity that the runoff changes with rainfall,to be specific,the downstream has the maximum runoff,the midstream runoff is the smallest,the upstream runoff is centered.Besides,there is a strong heterogeneity in the spatial distribution.(2)Synthetic Variation Diagnosis of Runoff Time Series Based on Gini CoefficientGini coefficient in economics is applied to hydrological runoff analysis to evaluate the uniformity of runoff changes.Secondly,based on the comprehensive variation diagnosis system oberserving the determination of the Gini coefficient of runoff at each station over the past 50 years,the paper is aimed to identify and diagnose the variation points of runoff time series in the Naoli River Basin through the three processes: preliminary diagnosis,detailed diagnosis and comprehensive diagnosis.Finally,the author finds that the variation year of Baoqing,Baoan,Hongqiling and Caizuizi stations are 1966,1966,1998 and 1990 respectively.At the same time,the paper analyzes the reasons for the changes based on the results.(3)Comprehensive calculation of ecological flow based on comprehensive index value methodFirstly,this paper applies different methods of ecological flow calculation to solve the ecological flow before and after the mutation point in the Naoli River Basin.Secondly,by calculating the ecological flow in different methods,the indicators can be obtained.Then the author gets the weights corresponding to each method through constructing comprehensive indicators.Finally,the author aims to take the the ecological flow before and after the variability point in the Naoli River Basin as the final ecological flow which are based on the weights and the corresponding ecological flow values.And then the author can analyze the ecological flow in the basin.After these analyses,the author finds that the ecological flow after the variation slightly reduce compared with that before the variation.However the natural flow can meet the demand of the ecological flow,which indicates the ecological flow in the Naoli River Basin is in a relatively healthy state.