Dynamic simulation and parameter estimation in river streams.

Abstract

Predictions and quality management issues for environmental protection in river basins rely on water-quality models. The key step in model calibration and verification is obtaining the right values of the model parameters. Current practice in model calibration is such that the reaction coefficients are adjusted by trial-and-error until the predicted values and measured data are within a pre-selected margin of error, and this may be a very time consuming task. This study is directed towards developing a parameter estimation strategy coupled with the simulation of water quality models so that the heavy burden of finding reaction rate coefficients is overcome. Dynamic mass balances for different forms of nitrogen and phosphorus, biological oxygen demand, dissolved oxygen, coliforms, nonconservative constituent and algae were written for a single computational element. The model parameters conforming to those in QUAL2E water quality model were estimated by a nonlinear multi-response parameter estimation strategy coupled with a stiff integrator. Yesilirmak river basin around the city of Amasya in Turkey served as the prototype system for the model development. Samples were collected simultaneously from two stations, and concentrations of many water-quality constituents were determined either on-site or in laboratory. This dynamic data was then used for numerical parameter estimation during computer simulation. When the model was simulated with the estimated parameters, it was seen that the model was quite able to predict the dynamics of major water quality constituents. It is concluded that the proposed method shows promise for automatically generating reliable estimates of model parameters.