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

Ramezani, Mostafa, Noori, Roohollah, Hooshyaripor, Farhad, Deng, Zhiqiang, Sarang, Amin
Hydrological sciences journal 2019 v.64 no.7 pp. 808-819
dispersibility, equations, hydrologic models, river water, rivers, solutes, Canada, United Kingdom, United States
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.