A 3-D numerical model has been developed to investigate transport processes of solute in a compound open channel. The Navier-Stokes equations have been numerically solved in conjunction with the linear and nonlineark-ε models to predict flow fields and turbulent parameters. The predicted velocity field and eddy viscosity are then used for solving the solute transport equation to predict solute transport rates. The hydrodynamic and solute transport models have been applied to the experimental studies undertaken by Wood and Liang (1989) and the results obtained from both the linear and non-lineark-ε models are compared with their results. This comparison clearly shows the influence of the secondary currents upon the mixing processes.