Determination Of Water Quality Model Parameter And Water Quality Prediction Mianyang Section Of Fu Jiang River

In view of the existing defects of multi-parameter estimation method, together with the varying characteristics of hydrology, water quality of Mianyang section of Fujiang and the necessity of parameter inverse problem, the multi-parameter ordinary differential equation model of water quality is established in the paper. Finite difference method and orthogonal rule method are combind to calculate the parameters of water quality model based on mathematics theory, which is compared to positive rule method, gradient descent, conjugate gradient method.The study shows that orthogonal rule method is one kind of accurate and fast numerical algorithm in calculating parameters of water quality model with clear superiority in the applicability of calculating method, the complex of computer programming, the quantity of total workload, typicality and the rationality of calculated results.It is concluded from model verification and sensitivity analysis that the error of the calculated value and the measured value is all below 25%, 61% of which is below 10%, indicating that structure of the model established is rational, values of parameters are credible, and the result of simulating can reflect the water quality condition of Mianyang section of Fujinng river.The prediction of water quality of Mianyang section of Fujiang river show that the water quality will deteriorate and the special sectional concentration of Bio chemical Oxygen Demand will surpassthe surface water quality standard (GB3838-2002) Class III(4mg/l), if economy develops in present pace and administration scale keeps existing level by the year 2001. Therefore, proper alteration in the industrial structure of Mianyang city must be taken, and the administer must be strengthened, then the water quality of Mianyang section of Fujiang river can be better and reach surface water quality standard (GB-3838-2002) Class II (3mg/l) .