Water Quality Models for Rivers and Streams. State of the Art and Future Perspectives

Mathematical models for water quality problems in rivers and streams are now an efficient tool in water resources management. Their basic principle is the differential equation of pollution transport, which can be integrated both in analytical and numerical form. From this equation the broad category of “fickian” models has been developed. The numerical procedures available so far are the finite difference and the finite element method. More recently the finite volume method has been proposed. The majority of practical cases consider the one-dimension approach, very significant in large rivers; but a better simulation of the real behaviour requests, at least, a two-dimension approach. The discharge of hot water is a frequent occurrence that gives rise to the thermal pollution. The water pollution problem in rivers and streams involve economical, social and political impact, for which the programming models can be very useful. To be efficient in the largest set of practical cases the model can benefit from sensitivity and uncertainty analysis. Research is now in progress aiming at improving the fickian models and at the identification of other kinds of models able to better understand the complex phenomena of pollution transport in rivers and streams.