Research On Multi-parameter Water Quality Model For Tidal-effect River Networks Based On MATLAB

The paper summarized the achievement of the hydraulic model and the water quality model research, analyzed each kind of models and algorithms. In view of the characteristic of river networks of the Pearl River Delta, the multi-parameter water quality model for tidal-effect river networks is established, providing the scientific basis for the tidal-effect river networks water environment management.The hydraulic model based on Saint-Venant equations is established. Saint-Venant equations are discretized by the use of Preissmann weighted implicit four-point scheme, and an algebraic equation set, which coefficient matrix is five opposite angles sparse matrix, is obtained. Using the MATLAB programming, the equation set is accurately solved. With relaxation iterative method, the hydraulic problem of any complex river networks is turn into the problem of a series of single river. The hydraulic model provides hydraulic data such as flow and volume for the water quality model. Considering tidal-effect river networks is well-mixed vertically and laterally, the water quality model based on the one dimensional migration diffuse equation is established. Water quality equations are discretized using implicit scheme, and an algebraic equation set, which coefficient matrix is three opposite angles sparse matrix, is obtained. A single river with known boundary can be solved by this equation set. For river networks, the mass-conservation equations of confluent point pollutant is added, concerning the inflow, outflow, source and lost. Items such as BOD₅, COD, DO, NH₃-N, TP, etc. can be simulated by the water quality model. The user-friendly Windows-based interface and data visualization is provided by the program.The model is applied to Shilong section of Dongjiang river networks, using the data of field survey in November, 2004. The result showed that the hydraulic model predicted value were basically tally with actual value and correctly reflected the tendency of ebb and flow, and the water quality model correctly reflected the change of pollutants which reverberate in the river networks due to ebb and flow.