Calculation Of Ecological Flow In Huaihe Basin Under Hydrological Variation Condition

Maintaining the health of river ecosystems is a huge challenge for China at present and in the future,and it is also a serious problem that China urgently needs to solve in order to realize the coordinated development of water resources,economy,society and ecological environment.Therefore,scientific and reasonable ecological flow is crucial.The article focuses on that it’s difficult to calculate minimum ecological flow by the hydrological methods.Firstly,the monthly average runoff datas that is from 1956 to 2000 about the seven controls sections are used to identify the variation point.Then,a SWAT hydrological model is constructed based on the identification of the runoff sequence variation points.Finally,the dynamic calculation method of ecological water demand is used to calculate the ecological flow of the control sections.The results show:(1)The runoff of the main stream and tributaries has significantly reduced in the basin above the Lutaizi station since 1956.A variety of variation point identification methods are used to diagnose the variation points of the seven control section runoff sequences.It shows that most of the variation points occurr in the 1960s,1980s,and 1990s.The precipitation-runoff double-accumulation curve is applied to diagnose the variation points caused by human activities.Except for the absence of significant variation in the curve at the HengPaitou hydrological station,the runoff sequence of the other six stations began to mutate in the 1960s,the time series before the first mutation point was considered as the natural runoff of the river.(2)The natural(before the variation)runoff sequence identified in the variation point identification is divided into a warm-up period,a calibration period,and a validation period.The model is calibrated and validated by the monthly runoff process in the order from upstream to downstream.The comprehensive analysis of the results of calibration and model validation results shows that the SWAT model is well applicable in the study area and it can be used to simulate the natural runoff sequences.(3)Based on the long-term natural runoff monthly process from 1956 to 2000,the paper uses the the dynamic calculation method to calculate the ecological flow..The minimum flow can be guaranteed during the general water period(September to March of the following year)and the breeding period(April to August).In terms of the minimum rate of ecological flow satisfaction,the satisfaction rate of Fuyang Station and Jiangjiaji Station has decreased significantly,and the results of Bantai,Hengpaitou,Xixian,etc.The satisfaction rates of Bantai,Hengpaitou,Xixian,Wangjiaba and Lutaizi Station don’t decrease significantly,which indicates that the river can still meet the minimum river ecological flow under the conditions of runoff variation.