Development And Application Of SWE-SPH-NSMI Water Quality Model

With the rapid development of social economy,human activities have caused irreversible harm to the water environment such as rivers and lakes.Studying the variation law of water quality concentration in rivers and lakes is of great significance to effectively control the water pollution of rivers and lakes.In this paper,SWE-SPH-NSMI water quality model is established,including SWE-SPH hydrodynamic model and NSMI water quality model.The NSMI water quality model considers eight water quality state variables:algae（Ap）,organic nitrogen（OrgN）,ammonia nitrogen（NH₄）,nitrate(NO₃),organic phosphorus（OrgP）,inorganic phosphorus（TIP）,carbonaceous biochemical oxygen demand（CBOD）and dissolved oxygen（DO）.The smooth particle hydrodynamics（SPH）method is used to discretize the shallow water equation（SWE）and the convection diffusion equation with source sink term,and the change of water quality concentration in the lake is simulated.The main research of this paper is as follows:（1）The CBOD and DO in the 1D SWE-SPH-NSMI water quality model are compared with the SP model and its analytical solution.It shows that the simulation results are completely consistent with the simulation value and analytical solution of SP model.（2）Taking Bohai Bay as the research object,this paper calibrates and verifies the model parameters of 2D SWE-SPH-NSMI water quality model under the condition of ideal terrain.The simulation results show that the concentration change curves of OrgN and OrgP are completely consistent with the simulation results in the literature,and the concentration change curves of Ap,NH₄,NO₃,TIP,CBOD and DO are basically consistent with the simulation results in the literature.The simulation results of SWE-SPH-NSMI water quality model are reasonable and accurate.（3）Based on the verified model,taking Xuanwu Lake as the research object and considering the actual terrain of Xuanwu Lake,the SWE-SPH-NSMI water quality model is calibrated and verified.The results show that the 82.6%of the absolute error between the simulated water level and the measured water level in the literature is less than 3.0 cm,and the maximum error is 3.5 cm.The simulated water level is basically consistent with the simulated and measured water level in the literature.The absolute errors between the simulated values of TN and TP in the model and the measured values in the literature are 3.77%and 11.29%,respectively,and the absolute errors are less than the absolute errors in the literature.The simulation results show that SWE-SPH-NSMI water quality model is reliable and the simulation results are accurate.