| Reservoirs have become one of the main sources of drinking water in China.Pollution of the water environment of reservoirs has occurred frequently in recent years.The most common of these is the eutrophication of reservoirs caused by excessive nitrogen and phosphorus contents.The water environment of the reservoir is complex,and once eutrophication occurs,it will be difficult to treat.The complex aquatic environment has created a unique distribution of pollutants in water bodies.Understanding the change of water quality indicators in the reservoir area is helpful for the management of lake and reservoir water environment.This study combines field monitoring and EFDC water quality model simulation to study and analyze the physical and chemical indexes of Gangnan Reservoir from 2018 to 2019,and to derive the water quality evolution law and distribution of water quality indicators in Gangnan Reservoir from 2018 to 2019.Make a preliminary evaluation of water quality safety,determine whether the water quality meets the standards,and discuss the water quality safety early warning technology.The main research results are:(1)On-site monitoring and analysis of the water body in Gangnan Reservoir area,the characteristics of the water quality of Gangnan Reservoir with seasonal changes and its vertical distribution characteristics are obtained.The temperature change of the Gangnan Reservoir is greatly affected by the temperature,and the seasonal difference is obvious.The water layer occurs in summer and autumn.The pH range is 7.5-9.2,which is weakly alkaline.The dissolved oxygen content in the reservoir area is high and the surface water is dissolved.The oxygen content is greater than 6 mg / l;the storage of nitrogen and phosphorus exceeds the surface water category ? standard,and the storage content basically reaches the surface water category ? standard,of which the total nitrogen exceeds the standard most,and it can reach the surface water environmental quality standard category ? standard at the maximum 13 times that of other indicators in the storage area,the quality of the water in the storage area basically meets the surface water environmental quality standard category II standards,the quality of the effluent water is good;other water quality indicators content will also vary vertically,thermal stratification of the water body is the cause The main reason for the differences in water quality in the vertical direction.(2)The hydrodynamic water quality model of Gangnan Reservoir is established,and the water quality of the reservoir is simulated and analyzed.Based on the EFDC software,the hydrodynamic water quality model of Gangnan Reservoir from 2018 to 2019 is established,and the measured data is adopted to use Delft3 D software to divide the grid.The measured water level,water temperature,dissolved oxygen,nitrogen,phosphorus,permanganate index and other parameters are used.Calibration and verification of the model,the simulation results agree well with the measured data;meanwhile,the model is used to simulate the water quality distribution of Gangnan Reservoir.The results showed that the pollutants gradually mixed and decreased after entering the reservoir area.The main mixed areas are S2 and S4.Outgoing water quality is good.(3)Based on the set model,the distribution of water pollutants in the reservoir area is simulated,and water quality safety warnings are provided for the water bodies.The pollutants are evenly distributed with the water body transported throughout the reservoir area after S1 and S2 are mixed and diluted.The good hydrodynamic characteristics of the reservoir area provide good water body exchange for the reservoir area,and the water quality in front of the reservoir dam is good.Model-based simulation forecasting ability using the EFDC model under suitable input data can predict the changes of upstream pollutants entering the water body to provide early warning of water quality in the reservoir area,so as to take targeted measures to reduce losses. |
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