This book presents numerical simulations of three-dimensional turbulent open-channel flows. In the simulations, Reynolds-averaged Navier-Stokes equations are solved with the Reynolds stress model for turbulence closure. The overall solution strategy is the SIMPLER algorithm, and the power-law scheme is used to discretise the convection and diffusion terms in the governing equations. The Reynolds stress model is applied to rectangular open-channel flows, partly-vegetated open-channel flows, and compound open-channel flows. The simulated mean flow and turbulence structures including streamwise mean velocity, secondary currents, turbulence intensity, and Reynolds stress, are provided and compared with measure data in the literature. As shown in this book, these comparisons reveal that the proposed Reynolds stress model successfully predicts the mean flow and turbulence statistics of turbulent open-channel flows.