Abstract: A two dimensional finite volume method and Osher scheme flow pollutant coupled numerical simulation on an unstructured grid is adopted and adapted to fit the complex planar geometry of the computational domain and the requirements of the prediction and evaluation of aquatic environmental quality.Developed in the framework of the finite volume method on an unstructured grid,the model transforms a 2 D problem into a series of local 1 D problems.By employing Osher type approximate Riemann solver,the model estimates the numerical flux of variables across the interface between cells with high accuracy.It is applied to water quality simulation of the Nanjing Reach of the Changjiang River.The simulated pollution area matches pretty well with the remote sensing satellite images,validating reasonability and applicability of the model. 

Key words: finite volume method, Osher scheme, unstructured grid, shallow water equation, convection diffusion equation, flow pollutant coupled numerical model