Numerical modelling-based comparison of longitudinal dispersion coefficient formulas for solute transport in rivers.

River water quality models usually apply the Fischer equation to determine the longitudinal dispersion coefficient (Dx) in solving the advection–dispersion equation (ADE). Recently, more accurate formulas have been introduced to determine Dx in rivers, which could strongly affect the accuracy of the ADE results. A numerical modelling-based approach is presented to evaluate the performance of various Dx formulas using the ADE. This approach consists of a finite difference approximation of the ADE, a MATLAB code and a MS Excel interface; it was tested against the analytical ADE solution and demonstrated using eight well-known Dx formulas and tracer study data for the Chattahoochee River (USA), the Severn (UK) and the Athabasca (Canada). The results show that Dx has an important effect on tracer concentrations simulated with the ADE. Comparison between the simulated and measured concentrations confirms the appropriate performance of Zeng and Huai's formula for Dx estimation. Use of the newly proposed equations for Dx estimation could enhance the accuracy of solving the ADE. [ABSTRACT FROM AUTHOR]