Secondary currents play a significant role in open channel flows. They directly influence the primary mean flow field, transport and mixing processes and the transversal alternation of bed shear stress. In this paper the flow field in a straight open channel with a rectangular geometry is calculated using two different numerical models. One solves the Reynolds-Averaged Navier-Stokes (RANS) equations, the other employs Large Eddy Simulation (LES). Both models use the finite volume method in combination with the SIMPLE scheme on a collocated grid. The RANS code applies the k-ω model with the extra turbulent anisotropy calculated from an explicit algebraic Reynolds stress model. The anisotropy is then added to the Navier-Stokes equations via source terms. An extensive collection of velocity and Reynolds stress data could be obtained from the numerical calculations, which gives valuable insight into the behavior of the two modeling approaches. The pattern and shape of the secondary currents is very similar with both models. There is also good agreement for the mean primary velocity. Deviations occur for some of the Reynolds stresses.