Eutrophication Numerical Simulation Research Of Yuqiao Reservoir

Lake (reservoir) eutrophication problem is becoming worse, getting more attention bythe public. Being different from river, lake (reservoir) storage more water, leadingslower water velocity and longer exchange period, therefore it can form a relativelyclosed ecological system. When the weather and the water quality factors change, theecological system is more easily affected. Then the water-bloom occurs. As being thewater source of Tianjin and the main storage reservoir of Yinluanrujin project, thewater-supply-safety of Yuqiao reservoir directly related to the social stability of theTianjin. Obviously, to establish a suitable water-bloom forewarning system forYuqiao reservoir has important significance.This research set Yuqiao reservoir as an example. The TLI method is used firstly totest the level of eutrophication. The result is mid-eutrophication, showing that thewater-bloom risk is big and a mathematical model to predict the algal growth trend isneeded. The establishment and application of model consists of three steps:(1) Through the weather, water quality factor and algae growth correlation research,the mathematical relation between algae growth and water quality and meteorologicalfactor were built. The CHLa-nitrogen nonlinear correlation equation with oneunknown quantity was established. Then the mass-balance-equation is given todescribe the algae reproduction-death process.(2)A2D coupled model which could simulate the algae’s growth and transportprocess is found by coupling the Mass Balance Equation with Convection-DispersionEquation and2D shallow water flow governing equations. By applying this model,the results are accurate and well matched with observed data, implying that themodified model could describe the algae’s growth and transport process properly.(3) This research used the model to simulate algae growth changes of Yuqiaoreservoir under adverse conditions. The corresponding disposal plans are givenaccording to the simulation results, which provided reference for water-bloomforewarning. The main innovation points: This research tried to establish Yuqiao reservoir nutrientcorrelation model and algae annual change trend, explore water temperature effect foralgae growth. On the basis of previous researches, numerical simulation method isemployed. Temperature influence coefficient expression is put forward to improve thealgal growth model of the accuracy of the predictions. Three rules were summarized:a) Higher water level will inhibit algae growth; B) Higher water temperature high willalso inhibit algal growth; C) Nutritive salt is not the main factors to restrain algaegrowth. Innovation points above provide theoretical foundation and reference topredicting and managing the eutrophication of Yuqiao reservoir.