Study On Hydraulic Regulation Of Level ? Water Pollution In Middle Route Of South-to-North Water Transfer Project

As an inter-basin water transfer project,Middle Route of South-to-North Water Transfer Project(MRP)possesses the characteristics of very limited available head,long distant,large scale,no on-line regulation reservoirs,and gravity flow flows along the whole line.The hydraulics problems are complicated.The water supply for MRP comes from Danjiangkou Reservoir,the water quality level is Grade ???,and it undertakes the important task of alleviating the serious water shortage in the north.However,due to the fact that the project is largely crossing South to North,and passing through numerous rivers,roads and bridges,sudden water pollution incident may occur.Under the sudden water pollution incident,how to deal with the water pollution incident through the correct emergency control strategy and form an effective risk defense system is particularly important.This is also the key to successful run of the MRP.Based on the Emergency Plan of Water Pollution Incident in the MRP(Q/NSBDZX G015-2014),based on the current research status of water pollution treatment in MRP,aimed at the emergency treatment for level III water pollution incidents that need to be solved for the MRP,while constant water depth in front of sluice gates was kept,a study on the law of migration and transformation of pollutants is carried out.Take full account of the structural characteristics of the engineering project,a one-dimensional unsteady flow model with complicated internal boundary conditions such as slucie gates,offtakes,inverted siphons and gradient sections was established,and a coupled one-dimensional water quality model based on equilibrium domain was also established.Compared with HEC-RAS,the coupled model was tested to have high calculation precision.It can be used in operation control simulation and emergency control research of MRP.The hydrodynamic parameters and water quality parameters that can affect the transport process of pollutant in the open channel were analyzed,and the functional relationship C=f(L,Q,k,b,H,T)was determined.Among them,the transport distance L,flow Q(Velocity u)and depth H(Storage V)can be used as control variables to participate in emergency regulation.In this paper,the effects of flow regulation and storage regulation on the transport process of contaminant under the controlled transport distance were studied.For the flow control method,both reducing flow to extend the transport time to enhance the role of self-degradation of pollutants and increasing flow to enhance the role of dispersion of pollutants were analyzed.As for the way of storage regulation,the dilution effect of increasing storage of channel by diverting and retaining was analyzed.Integrated the advantage of long-distance water transfer project with multi-drainage pools and the ability of channel's own capacity adjustment,the flow control method plays a stronger role than the storage control method.The level ? water pollution emergency control plan for the MRP was studied.Aimed at the characteristics of large water transmission in the MRP,too many sluice gates and offtakes,and high control requirements,a control strategy that dividing the hydraulic control unit based on the hydraulic characteristics of the offtakes was proposed to limit pollutants into the hydraulic control unit.Under the premise of not significantly affecting the run of upstream and downstream of the control unit,by exerting the regulation role of the sluice gates and offtakes,the channel's own adjustment capacity is fully utilized to maintain the dynamic balance and stable water level of the channel,the target of water pollution emergency treatment was realized.Three specific implementation methods were put forward,and simulation tests were conducted on the Beijing-Shijiazhuang channel.Studies showed that the three methods can be applied to different operation conditions.Compared to the traditional schemes such as opening the exit gate or closing the sluice gates,the three methods did not need to abandon water and did not cause significant fluctuation in the water level.The impact to upstream and downstream of control unit is also unconspicuous.