A one-dimensional model for water quality simulation in medium- and small-sized rivers

While studying water quality in the Tatara river, we realized that the river has various hydraulic and topographic characteristics when flowing through different regions. Because of these specific characteristics, the application of the existing models for simulation of its water quality may not be appropriate due to limitations in the models themselves. Therefore, we developed a mathematical model that is suitable for short-term simulations of water quality in rivers with characteristics similar to the Tatara river. The main foundation of the model is the one-dimensional transport equation established on the basis of the mass conservation law. To solve this equation numerically, it was discretized by the method of finite-difference approximations, and an algorithm has been programmed in Fortran 90. To verify the model, the Tatara river was chosen as a case study. Water temperature, dissolved oxygen, hydraulic parameters in four typical blocks of the river, and meteorological data of the study area, have been observed and used to test the model. By calibrating the model with different series of data collected from the designated blocks, all results have shown a good fit between simulated data and the observed one. Therefore, the model could be a reliable tool for simulating water quality in medium- and small-sized rivers over a short-term period. This research has also indicated the changing tendencies of water temperature and dissolved oxygen in Tatara river in response to different meteorological patterns over a daily 24-h period. Besides, the model could be improved to simulate other water quality variables, which would be studied further.