Development and application of an eutrophication water quality model for river networks

The Preissmann implicit scheme was used to discretize the one-dimensional Saint-Venant equations, the river-junction-river method was applied to resolve the hydrodynamic and waterqualitymodel for rivernetworks, and the key issues on the model were expatiated particularly in this article. This waterquality module was designed to compute time dependent concentrations of a series of constituents, which are primarily governed by the processes of advection, dispersion and chemical reactions. Based on the theory of WaterQuality Analysis Simulation Program (WASP) waterqualitymodel, emphasis was given to the simulation of the biogeochemical transformations that determine the fate of nutrients, in particular, the simulation of the aquatic cycles of nitrogen and phosphorus compounds. This model also includes procedures for the determination of growth and death of phytoplankton. This hydrodynamic and waterqualitymodel was applied to calculate two rivernetworks. As illustrated by the numerical examples, the calculated water level and discharge agree with the measured data and the simulated trends and magnitudes of waterquality constituents are generally in good agreement with field observations. It is concluded that the presented model is useful in the pollutant control and in the determination of pollutant-related problems for rivernetworks.