Research On The Variation Regularity Of Hydrodynamics And Contaminants Under Slow Storing And Fast Release Conditions

Slow storing and fast releasing system refers to construct gates on the river to store up small upstream inflows.When the accumulated water meets the quantitative requirement,the erosion of river pollutants is realized by opening the gate quickly and releasing the flow.In order to enrich the research on slow storing and fast releasing system,this research stored the water of Xi ’an moat in cylinders to check the water quality regularly,and obtained the regularity of water qual ity change with time under static conditions.A numerical model of flume was built by Flow-3D,and the model was used to simulate the influence of initial downstream depth,gate width and the amount of released water on the hydrodynamic characteristics under fast released condition.An improved box model was proposed based on the research of the regularity of water quality change with time under static conditions.Taking the reach from 1#dam to 2#dam of Xi ’an moat as the research area,the model was applied to simulate the variation regularity of water pollutants from September 11 to 25,2020 under two conditions of normal overflow and slow storing and fast releasing.This research illustrate the following conclusions:(1)Under static conditions,water quality indexes such as TN,TP,NH4+-N,CODMn will increase with time due to atmospheric sedimentation and organic sedimentation of pollutants,and the quality of water with reclaimed water as supplementary source is more likely to deteriorate than water with reservoir water as supplementary source.The concentration of each index in the lower layer of the water sample increased rapidly,followed by the middle layer and the slowest in the lower layer.(2)The hydrodynamic characteristics under fast released condition can be improved by increasing the gate width,increasing the discharge volume and decreasing the initial depth of the downstream water.(3)Compared with normal over-flow condition,on September 25th,TN,TP,NH4+-N and CODMn decreased by 6.35%,8.99%,11.12%and 5.11%,when the water storage time of slow storing and fast releasing system was one day.When the water storage time is 2 days,TN,TP,NH4+-N and CODMn decrease by 6.28%,8.86%,10.89%and 5.05%.When the water storage time is 3 days,TN,TP,NH4+-N and CODMn decrease by 6.20%,8.70%,10.61%and 4.96%.With the decrease of water storage time,the amount of released water decrease,consequently,with the decrease of released water,the improvement effect of slow storage and quick release system on water quality is enhanced.(4)The slow storing and fast releasing system can improve or maintain water quality by speeding up water flow,reducing water retention time and shortening the process of water quality deterioration.When constructing the slow storing and fast releasing system,The reasonable amount of released water should be determined based on the actual water quality conditions,and the hydrodynamic improvement effect can be improved by changing the initial downstream depth,gate width or other parameters.