A model for numerical simulations of solute transport in vegetated open-channel flows is proposed. The Reynolds-Averaged Navier-Stokes model is used for the flow analysis. For the turbulence closure, the Reynolds stress model is used, and the generalized gradient diffusive hypothesis is used to close the Reynolds-averaged advection/diffusion equation. The developed model is applied to an experimental case of solute transport in turbulent open-channel flows over submerged vegetation reported by Ghisalberti and Nepf (2005). The simulated distributions of mean concentration along the streamwise direction are compared with measured data, showing a good agreement. In addition, numerical simulations reveal that the pattern of secondary currents in vegetated open-channel flows is significantly different from that in plain open-channel flows. Using the simulated results, the vertical turbulent Schmidt number for the vegetated open-channel flow is estimated and a value of 0.58 is obtained. This value can be compared to 0.47, which was obtained by Ghisalberti and Nepf (2005) using laboratory data.