Research On Integrated Regulation Of Water Quality And Water Quantity In Plain River-net Areas

Plain river network area has superior natural conditions,the social and economic developed,having more population.The industry and agriculture is developing rapidly.But its water resources are often hard to bear the huge environmental pressure.With the constant expansion of the city size and the continuous intervention of human activities,the sluice and pumping stations continue to increase.The river connectivity becomes worse,coupled with large number of point sources and non-point source pollutants from city discharged into the river,leading to the plain river network water environment problem is very serious.As a typical plain river network area,the Haihe River Basin,influenced by urbanization,has just a single river pattern.The problem includes: many artificial disturbances,rain and sewage discharging,and non-point source pollutants directly into the river,the small ecological runoff and the poor reoxygenation capability.There are many serious water environmental problems.Therefore,it is of practical significance to purify river water quality,enhance river connectivity,enhance river network water environment and improve regional water ecology,and carry out research on comprehensive regulation of water quality and quantity in plain river network area with Haihe River as an example.Based on the Saint-Venant equation and the one-dimensional convection-diffusion equation,a one-dimensional coupled model of hydrodynamic and water quality is established in this paper.By simulating water quality improvement measures such as diversion of water diversion from Luanhe River and trunk and tributaries,We can analyze the water body displacement characteristics and water quality change law,and on this basis,using orthogonal test method to choose the best water quality and comprehensive water quality control program to improve the water quality of the Haihe River mainstream region.The main contents and conclusions are as follows:(1)Based on the topographic data,water level and flow data and water quality data,a one-dimensional hydrodynamic and water quality coupling model for the river networks of the Haihe River is established.Using the measured water level data,water flow data and water quality data in 2015 and 2014,we rate and verify the hydrodynamic parameters and water quality parameters.The measured values are in good agreement with the simulated values.The model can reflect the hydrodynamic and water quality characteristics of the study area.(2)Through the simulation and calculation of different water transfer schemes,the water quality changes of Haihe River tributaries are analyzed and discussed.When the decay of pollutants is not considered,the change of water quality is achieved by the convective diffusion of pollutants.In the same diversion time,the bigger the water flow is,the better the replacement effect of water body is.When the diversion flow is the same,the longer the diversion time is,the better the water replacement effect is;When considering pollutant decay,the change of water quality is affected by the pollutant convective diffusion and pollutant decay.The diversion flow rate determines the rate of water exchange in the initial period of water diversion.The length of water diversion.(3)Considering factors such as diversion flow,diversion time,two-way dispatching method and circulation path of dry-branch and tributaries,three-factors four-levels orthogonal test table is put forward based on orthogonal test method,and 16 combinations are developed under each path.The optimal water transfer scheme and the optimal circulation path are obtained by using one-dimensional hydrodynamic and water quality coupling model to calculate the optimal index of each scheme.