Author(s): Mucherino Carmela; Palumbo Anna; Pianese Domenico
Linked Author(s): Domenico Pianese
Keywords: Water Quality Modelling; Lagrangian Approach; Pollutant Transport; Rivers Pollution
Abstract: In recent years, the significant worsening of water quality in rivers is receiving more and more attention by the community, scientists and engineers. There is a great necessity of simple and powerful quality models for continuous surveillance and on-line decision making. In addition, these models are required to provide invaluable assistance to those (governmental boards, industries, scientists, etc. ) involved in planning environmental improvements by locating suitable sites for waste water discharges or appropriate sites where it is possible to derive from rivers water for drinking or irrigation water supplies. In this work, it is proposed a new numerical model for pollutant propagation simulation in natural and artificial free surface networks denominated QualSim-FSN. The numerical model was set up in two versions (QualSim-FSN1 and QualSim-FSN2), both based on two successive modules: the hydraulic and the quality modules. The first module is the same for both versions of the model and it is based on an application, to one dimensional unsteady free surface flows equations, of the Finite Volume Method (FVM), able to simulate both natural and artificial free surface networks, eventually characterised by complicated morphology of the channels and/or many discontinuities in the flow. The second one is based on the use of a lagrangian-type approach and was developed in two different versions characterised by two different techniques to determine the parcels length. This approach was chosen for reducing numerical dispersion and loss of pollutant mass as much as for simplifying and also for accelerating the calculations. Finally, in order to evaluate the efficiency, validity and accuracy of the models proposed, they are compared with two other models: QUAL2K and BLTM, that are currently the standard for river water quality modelling. Since the primary goal of this work is to compare river water quality models, by focusing the attention on the problem of reducing numerical dispersion terms in advection. Four numerical experiments are proposed. The comparisons, carried out with the aid of a few analytical solutions available for each study-case, show the capability of both versions of the model proposed to simulate, better than QUAL2K and BLTM models, the propagation of a pollutant, without loss of mass, numerical dispersion and without shift and reduction of the concentration peak.
Year: 2007