The Impact Of The Poyang Lake Hydraulic Project On Residence Time And Water Supply

Poyang lake is the largest freshwater lake in China.The scheduling of the Poyang Lake Project will affect the hydrodynamic situation in the lake area.The change of water level has an impact on farmland irrigation and urban water supply and the change of flow will change the water exchange capacity lead to different ecological environment effect.Based on the construction of Poyang Lake two-dimensional hydrodynamic model which is verified through the measured water level of different stations to investigate the hydrodynamic effects,discusses the influences of water supply and analyze the effect of residence time.It provides necessary support for the possible impact of the project.The main research results and conclusions are as follows:(1)According to the dispatching plan of the Poyang Lake project,calculation conditions were set up to simulate the impact on dynamics.Under the influence of the hub,from September 15 to October 20,the whole lake maintain a high water level.The scope of the dispatch involves most lake area.From October 31 to March,with the decrease of the dispatching water level,the affected area gradually decreased and stabilized,mainly affecting the channel and some main lake areas.The influence of hub scheduling gradually decreased from north to south,presented as Xingzi> Duchang> Tangyin> Kangshan.The spatial difference of the water level is reduced.the range of high flow velocity in Poyang Lake has decreased,while the range of stagnant water area has expanded.The spatial difference of flow velocity is reduced.(2)Based on the constructed two-dimensional hydrodynamic numerical model of Poyang lake and combined with advection-dispersion equation to simulate the residence time of Poyang Lake under typical year to qualitatively analyze the influence of hub scheduling on the residence time in different water areas.Under the influence of the hub,the residence time in the eastern area of the river channel and the northeast bay increased,while the residence time in the Bang lake,sand lake and Pa lake in the Poyang lake decreased.This is related to the elevation of water level,which helps to establish the hydraulic connection between the shallow lake and the main lake area,and improves the water exchange of the shallow lake.(3)The research divided the area into six subzones based on the hydrogeomorphology and combined with flushing homogeneity curve(FHC)and flushing deviation index(FDI)to analyze the influence of hub scheduling on the residence time.Under the influence of the hub,the residence time in autumn and winter mainly affects Zone I,Zone II,Zone III and Zone IV.For Zone V and Zone VI,there is a slight impact in autumn,and winter is almost unaffected.In autumn,the residence time in Zone I,Zone II and Zone III is generally increased,while the residence time in Zone IV is decreased.In winter,the residence time in Zone I and Zone III is generally increased,and the residence time in Zone II and Zone VI is decreased.The shape of the flushing homogeneity curve is similar to that of the non-hub impact.The FDI value changes in autumn involve Zone I,II,III,and IV,and the FDI value increases and the spatial heterogeneity increases.However,the change of FDI value in winter involves zone I and II,the FDI value is basically reduced,and the spatial heterogeneity is reduced.(4)Based on the constructed two-dimensional hydrodynamic numerical model of Poyang Lake,the influence of hub scheduling on the water use in the Poyang Lake area was selected by typical year analysis.The Xingzi County and Duchang County in the Poyang Lake area were used as typical counties for the irrigation and the urban water supply situation.Under the influence of the hub,the water level rise is conducive to improving the irrigation and the urban water supply situation in Xingzi County and Duchang County.the average external water level of the water intake of the embankment is increased by 0.81~3.83 m and the average external water level of each water plant's water intake rises above 13.79 m.At the same time,The number of days of difficulty in taking water is reduced,and the water level can basically meet the minimum water intake requirements,which is conducive to improving the shortage of water resources in the dry season of Poyang Lakeand improve the guarantee rate of water production for daily production.