Algal Blooms And Movement In The Reservoir And Controlling Water Quality In The Main Stream Of A River

Eutrophication and algal blooms have become important environmental problems worldwide.Algal blooms,especially those in drinking water sources,have an important impact on biodiversity and the function of water ecosystems,and thereby seriously threatening human health and economic development.The water storage capacity of lakes and reservoirs is relatively large,and the water flow is slow with long water exchange cycles;therefore,the ecosystem is relatively closed.With changes of the weather,water quality and other factors,lake and reservoir ecosystems are easily affected,and thus leading to algal blooms.In addition,since the process of urbanization and human activities are increasingly intensified,the urban river water flow affected by long-term human disturbance and non-point source pollution into the river is slow,and the deterioration of water quality is also very serious.Therefore,analyzing the characteristics of algae and other pollutants in reservoirs and rivers related to drinking water,and simulating the water quality in reservoirs and urban rivers under different conditions are of great significance to the maintenance of water security and social stability.Taking the Yuqiao reservoir and Haihe River in Tianjin as research areas,the two-dimensional coupled model of algae growth and migration and the one-dimensional river hydrodynamic and water quality model were established respectively.Then the characteristics of algal bloom,the temporal and spatial distribution of alga,and the migration and diffusion of pollutants in the main stream of Haihe River were discussed.The main contents and results are as follows:(1)Based on the stepwise cluster analysis algorithm,the prediction model of algal bloom was established and the reliability of the model is verified by the measured values of chlorophyll-a concentration,then the comprehensive growth coefficient of algal was extracted.(2)The two-dimensional coupled model of algal bloom and migration was mainly established based on the two-dimensional shallow water equation,the convectiondiffusion equation and comprehensive growth coefficient of alga.Then the temporal and spatial distribution of alga under different meteorological conditions was analyzed.The results showed that from the end of August to Mid September,the chlorophyll-a concentration is high in the northwest,the northern coast and the center of Yuqiao Reservoir,and corresponding measures should be taken to prevent the outbreak of algal bloom.(3)The migration and land conversion of pollutants in the downtown of Tianjin was simulated,and the output of runoff and variations the concentrations of pollutants could provide lateral inflow conditions for the water quantity and quality model in Haihe river.The one-dimensional water quantity and water quality model in Haihe river was established,calibrated and validated with the measured data of water level,river flow and water quality.(4)It was assumed that there were algal blooms between the cross section of Sanchakou and Daguangmingqiao in Haihe river,and then different water diversion schemes used for controlling algal blooms in Haihe river were compared and optimized.A series of feasible water cycle paths and water diversion schemes were proposed based on different water diversion schemes and sluice dam operation modes,and the best scheme to reduce the pollutant concentration in the main stream network of Haihe River was selected.It could be seen that The flow and duration of water diversion are the main factors influencing the average concentration of pollutants,and the optimal water circulation path in Haihe river is : Dongchangyin River Pump Station-Dongchangyin River-Nanyun River-Wei Jin River-Fuxing River-Haihe River.