| The water diversion project from Hanjiang to Weihe River is a key project to realize the optimal allocation of water resources in Shaanxi Province.It can solve the water shortage problem in the Guanzhong area,but with the rapid development of social economy,water environment problems with water supply quality security as the core may arise.The research takes the water diversion system from Hanjiang to Weihe River(Huangjinxia Reservoir,Sanhekou Reservoir,water delivery tunnel)as the research object,using the method of constructing the hydrodynamic-water quality numerical model of the water diversion system from Hanjiang to Weihe River,the topological structure of the water diversion system was analyzed,the water environment evolution law of the water diversion system under the joint operation of four water sources was analyzed,and carried out a simulation and prediction study of sudden water pollution incidents.Provide reference for the operation management and water quality safety guarantee of the water diversion system from Hanjiang to Weihe River.The main work and important conclusions of this paper are as follows:(1)Analyze the temporal and spatial distribution of current water quality in water source areas.Using multivariate statistical analysis methods to evaluate the water quality of the water source area,it can be seen that the water quality indicators of the water source area have significant differences in both time and space scales;the hierarchical cluster analysis results show that the water quality indicators are clustered into two categories in time:non Flood season(November to June)and flood season(July to October),spatially clustered into two categories:Hanjiang tributaries and Hanjiang main stream;Except for TN,the other water quality factors all reached Class II water quality standards.The water quality during the flood season is worse than that of the non-flood season.The water quality of the tributaries of the Hanjiang River is better than that of the main stream of the Hanjiang River.The water quality of the Sanhekou reservoir area is better than that of the Huangjinxia reservoir area.The comprehensive water quality category of the water source area meets the requirements of the water function zone.(2)Analyze the topological structure of the water transfer system.The project diverts water from the Huangjinxia Reservoir area through the pumping station to the water conveyance tunnel,and gathers the water diversion in the Sanhekou Reservoir area at the Sanhekou control gate(Part of the water source from the Huangjinxia that exceeds the water demand in Guanzhong is pumped to the Sanhekou Reservoir through the pumping station for storage).Then draw the water to Huangchigou by gravity and connect it to the water supply network in Guanzhong area.(3)Predict the evolution of the water environment under the normal operation of the water transfer system.By constructing a water environment model of the water diversion system based on the hydrodynamic process,the water quality distribution characteristics of the water diversion system under the joint operation of different hydrological years are quantitatively analyzed.The following conclusions are drawn:the distribution of pollutants in the water transfer system from the end of the reservoir to the front of the dam to the outlet of the water transfer tunnel has a decreasing trend.After the water diversion in the Huangjinxia reservoir area gathers the water source in the Sanhekou reservoir area,the water quality has a significant improvement effect.According to the distribution of NH3-N in the water transfer system in the rainy year,the concentration from the tail of the Huangjinxia Reservoir to the front of the dam decreased from 0.248mg/L to 0.242mg/L.The water source in the Huangjinxia reservoir area enters the water conveyance tunnel and is controlled at the mouth of the Sanhe River.The concentration of the sluice was reduced to 0.203mg/L after the water from Sanhekou was converged.From the COD distribution,it can be seen that from the tail of the Huangjinxia reservoir to the front of the dam,the concentration dropped from 11.212mg/L to 11.084mg/L,and the concentration dropped to 10.284mg/L after the Sanhekou water source converged at the Sanhekou control gate.It can be seen from the distribution of TN that from the end of the Huangjinxia reservoir to the front of the dam,the concentration dropped from 2.309 mg/L to 2.095 mg/L,and the concentration dropped to 1.346 mg/L after the Sanhekou water source converged at the Sanhekou control gate.Through the statistical analysis of the water quality simulation results of different hydrological years,it can be concluded that under the normal operation of the project,NH3-N and COD can meet the water quality requirements of the water supply,but the TN does not meet the water quality requirements,and measures need to be implemented to reduce TN and meet the standards.(4)Predict the evolution of pollutants under sudden water pollution incidents in the water transfer system.Based on the constructed water transfer system model,the migration and transformation of pollutants under the sudden water pollution incident scenario of sudden toxic chemical leakage and abnormal discharge of sewage was simulated and analyzed.The following conclusions are drawn:In the context of the sudden 10t nitrobenzene leakage incident,the accident site occurred at the Hanjiang Bridge,Jinshui River in the Huangjinxia Reservoir,and Wenshui River in the Sanhekou Reservoir.The pollution duration of the water intake in front of the dam was 38h,96h,74h,it can be concluded that the sudden water pollution incident of the Jinshui River in the Huangjinxia reservoir will pollute the water intake for a longer period of time.Once a pollution accident occurs,the risk is greater.Under the scenario of sudden sewage abnormal discharge,under the condition of incoming flow of 530.33m3/s and 43.27m3/s,the pollution length of the reservoir area is 45km and 25km respectively.Affected by degradation,all have no effect on the water quality at the water intake in front of the dam.According to the simulation study of sudden water pollution incidents in the water conveyance tunnel,under the scenarios of 10m3/s,40m3/s,and 70m3/s of water transfer from the Huangjinxia Reservoir,the time for the pollutants to transport and diffuse from the water intake of the Huangjinxia Reservoir to the exit of the tunnel is respectively 26h,16h,13h;under the scenarios of 10m3/s,40m3/s,and 70m3/s of water transfer from Sanhekou Reservoir,the time for pollutants to transport and diffuse from the water intake of the Sanhekou Reservoir to the exit of the tunnel is respectively 21h,13h,10h. |
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