Diffusion Prediction And Emergency Operation For Sudden Water Pollution Accidents In The Main Canal Of Middle Route Of South-to-North Water Diversion Project

The Middle Route of the South-to-North Water Diversion project(MRP)can address water shortages in Henan,Hebei,Tianjin,and Beijing,and has brought great social,economical,ecological and environmental benefits since its operation,which is of important strategic significance to China.However,there are many potential risks of sudden water pollution accidents along the main canal of the MRP,which may endanger the safety of water supplies.In order to deal with sudden water pollution accidents rapidly,scientifically and rationally to reduce the losses and ensure the safe operation,this paper deeply studied the diffusion prediction and emergency operation methods for sudden water pollution accidents.The main achievements are as follows:Firstly,by using the layered structure and modular modeling method,the one-dimensional hydrodynamic and water quality model was developed in the main canal of the MRP based on its characteristics,e.g,containing many types of structures.The parameter identification method for discharge formulas of gates using the least squares method based on measured data was developed to calibrate the coefficients of 61 check gates(that divide the canal into pools),and the hydrodynamic model was proved to be relibale using measured data.Secondly,the pollutant diffusion processes under numerous sudden water pollution accident scenarios were compared and analysed,and the rules of pollutant diffusion were summarized by using three characteristic parameters,i.e,arival time,peak concentration and time to peak concentration.The rapid prediction methods of these three characteristic parameters for sudden water pollution accidents were developed based on dimensionless analysis,respectively.And then,the rapid prediction formulas for sudden water pollution accidents in the main canal of the MRP were determined using the scenario simulation results.Thirdly,in the accident pool(where the accident occurred),four closing modes for the two check gates(synchronous with the same speed,asynchronous with the same speed,synchronous with different speeds,asynchronous with different speeds)and their combine use with drainage gates(that drain water under emergency conditions)were proposed,and the hydraulic response characteristics under numerous emergency operation scenarios were compared and analysed by using four characteristic parameters,i.e,drawdown rate of the downstream water level of upstream check gate,maximum rise of the upstream water level of downstream check gate,final rise of the upstream water level of downstream check gate and stability time,then the emergency operation guideline was summarized.In the upstream section of the accident pool,the emergency operation method regulating pool volume to reduce abandoned water based on ensuring the normal water supply of diversion gates(that transfer water to cities along the canal).In the downstream section of the accident pool,following the emergency operation method to maintain the constant upstream water level of each check gate,the calculation method of volume of water supply was proposed.Furthermore,the evaluation index system representing the implementation effects of the emergency measure was established,and the evaluation method was developed based on the analytic hierarchy process(AHP),the entropy method and the technique of order preference by similarity to the ideal solution(TOPSIS).Therefore,the 'safaty-economy' multi-objective coordinated emergency operation method was proposed.Finally,considering the project characteristics and existing automatic system,the workflow of the emergency operaion and management for sudden water pollution accidents was analysed,then the emergency operaion and management system for sudden water pollution accidents was designed,in which,the framework consisting of four layers of 'database-model integration-function-user interface',functions consisting of the whole process of emergency operaion and management for sudden water pollution accidents,and key technologies ensuring the smooth development and successful application of the system were proposed.