Model Study And Risk Assessment Of River Water Quality In Northwest Hebei Province

Due to the rapid development of China’s economy,it has gradually caused environmental pollution,especially the water environment pollution.The northwestern part of Hebei Province refers specifically to Zhangjiakou City and its periphery,which is located in the northwestern part of Hebei Province.It is located at the intersection of the Inner Mongolia Plateau and the North China Plain.It is a cold temperate continental monsoon climate.It has less wind and rain throughout the year,the air is very dry,and the evaporation is large.Most rivers often have a current cut.The Yongding River system is located in the southwest of Beijing.The whole river is located in Zhangjiakou City,northwestern Yunnan.The main tributaries are the Huliu River,the Yanghe River,the Sanggan River,the Lishui River and the Qingshui River.Among them,the Yanghe River and the Sanggan River It has a certain representativeness in the northwestern part of Yunnan,so it is selected as a specific research object to establish a suitable water quality model and provide scientific basis for river water pollution prevention and management.It has practical significance.Taking this as a background,this dissertation firstly monitors the water quality indicators of the monitoring sections of the selected rivers in 2014 and 2015.In order to facilitate the simulation calculation,the river network should be generalized.Therefore,the shape of the river is generalized to the level.The bottom slope and the trapezoidal section are rivers with several different sections connected in series.The distance between the selected river sections is 1000 m,the total number of rivers is 2,and the boundary points are 4;Secondly,the one-dimensional water quality model of the river is established by using the monitoring data of the recent year and the characteristics of the Yanghe and Sanggan rivers collected in northwest Hebei,which are discretized by the implicit finite difference scheme and solved by Thomas’ "catch-up method".The VC6.0 software is used for programming,and the calculated simulation values and measured values are calculated.The values were compared and analyzed.The results showed that the simulated values of the three water quality indicators of the seven monitoring sections were basically consistent with the measured values.Most of the relative errors were within ±20%,and the overall error did not exceed ±40%,so the water quality model calculation accuracy was met.The requirements are again;the sensitivity analysis of the parameters of the established water quality model and the test of the model are again performed.The sensitivity analysis results indicate the image.The largest is the water flow rate Q,followed by the longitudinal diffusion coefficient E,and the result of the test is that the relative error of more than 90% of the points is less than ±20%,and all the simulation results are within ±40%,which is The river network studied in this project is satisfactory.Finally,the water quality risk assessment of the water quality index of each monitoring point in the Yanghe River and Sanggan River Basin in April 2015 was carried out,and the fuzzy reliability of the three water quality indicators.Both are above 90%,and the risks are very low,so the probability of reaching the surface II water quality standard is very high.Therefore,according to the established water quality model and the existing section division,boundary conditions,rate parameters and the discharge points of the pollution sources collected in the later stage,each section of the Yanghe and Sanggan River basins in the northwestern Yunnan can be calculated.The concentration value of the spatial section at any simulation time during the year can be used to influence the spatial and temporal variation of pollutant concentration in the water body due to the discharge of pollution sources in different river sections.It can also be based on the simulated data and the actual required critical water quality allowable concentration and the area.The classification of river water quality functional zones is carried out to evaluate the water quality risk,to identify unreliable water quality risk points,and to further pass the river water quality by discharging the pollutants of the limit enterprises or concentrating the domestic sewage of nearby residents or controlling the river flow.Pollution prevention work.