Study On The Influence Law Of Runoff Jacking In The Tail Area Of Ganjiang River In Poyang Lake

Backwater is a common phenomenon at the intersection of Poyang Lake and Ganjiang River.The high water level of Poyang Lake blocks the entrance of Ganjiang River to the lake,which causes the water level of the river to rise and forms backwater phenomenon.It often occurs at the intersection of lakes,rivers and seas.As the largest river in Jiangxi Province,Ganjiang River is an important tributary of the middle and lower reaches of the Yangtze River,and also plays a role in communicating the water system of Poyang Lake,the largest freshwater lake in China.Its flow movement law,hydrological conditions are more complex and the topping phenomenon is very obvious.The influence of crest support phenomenon often occurs in Tailu area of Ganjiang River,which is an important reason for complicated flow conditions into Poyang Lake.Especially during flood period,affected by backwater crest support,water level in the lake will be higher than upstream water level,causing serious backwater phenomenon,raising flood water level and increasing flood disaster risk.This paper attempts to quantitatively analyze the regularity of runoff jacking in the Tailu area of Ganjiang River and Poyang Lake,so as to provide reference for local governments to plan and manage the Tailu area of Ganjiang River.In this paper,two-dimensional hydrodynamic model simulation is used as the starting point to carry out qualitative and quantitative analysis of reflux,confluence and jacking phenomena.At the same time,aiming at the section from Waizhou to Wucheng in Tailu area of Ganjiang River,we try to carry out correlation analysis and establish multiple regression equation to quantify the jacking phenomenon,and fit it into functional relation by means of multiple stepwise regression analysis,so as to get the influence of the jacking on the diversion of main branches and branches of Tailu River of Ganjiang River and the general rule.The main research contents and achievements are as follows:(1)First,analyze the measured data.Based on the analysis of flow rate and water level change rate and flow rate of each section in the Tailu area of Ganjiang River for many years,this paper sorted out and drained the 30-year hydrological measured data,selected the representative year and summarized the actual occurrence conditions and time of the backflow jacking.According to the abnormal change of water level-flow relationship in the representative year,the relationship and rules of the jacking are concluded in the special plenty and the special plenty.During the four representative years of high,flat and dry,the phenomenon of reflux jacking lasts for a long time and has a wide influence.During the flood season,when the flow in the upstream outer States drops below 1000m3/s,the obvious phenomenon of reflux jacking will occur.(2)Secondly,the data collected are used to model..According to the topographic data of the research area,the measured hydrological data are simulated by two-dimensional hydrodynamic model.The main branch of Ganjiang River is taken as an example to study and analyze.The process of flow level change is well simulated by boundary condition determination,grid division,roughness determination and final verification.The simulated data shows that when the flow of upstream and downstream States is less than 900 m3/s during high water period.At the entrance of the main branch to the lake mouth,there will be a very obvious phenomenon that the Poyang Lake will flow back to the top of the Boyang River and Ganjiang River.After the top is restored to the water level station of Nanchang Station,it will flow into the middle branch and the South Branch together with the upstream water.causing the two branches to restore the top of the Poyang Lake.(3)Finally,the correlation analysis between flow rate,flow rate and water level is carried out based on the obtained simulation data.It is concluded that discharge is the key factor to determine the height of the top support.Empirical formulas of water level and flow in the time of top support phenomenon and in the time of no top support phenomenon in the main branch area of Ganjiang River are obtained by means of multiple non-linear equations.This formula can verify the height of the top support water level in the main branch section of Tailu River of Ganjiang River.