The modelling of solute transport in rivers is usually based on simulating the physical processes of advection, dispersion and transient storage, which requires the modeller to specify values of corresponding model parameters for the particular river reach under study. In recent years it has become popular to combine a numerical solution scheme of the governing transport equations with a parameter optimisation technique. However, there are several numerical schemes and optimisation techniques to choose from. The chapter addresses a very simple question, namely, do we get the same, or do we get different, parameter values from the application of two independent solute transport models/parameter optimisation techniques to the same data? Results from seven different cases of observed solute transport suggest the latter, which implies that parameter values cannot be transferred between modelling systems.