Accuracy of the kinematic wave and diffusion wave approximations for time-independent flows with infiltration included

Errors in the kinematic wave and diffusion wave approximation for time-independent (or steady-state) cases of channel flow with infiltration were derived for three types of boundary conditions: zero flow at the upstream end, and critical flow depth and zero depth gradient at the downstream end. The diffusion wave approximation was found to be in excellent agreement with the dynamic wave approximation, with errors of less than 1.4% for KF02 greater than or equal to 7.5, and up to 14% for KF02 less than or equal to 0.75 for the upstream boundary condition of zero discharge and finite depth, where Kis the kinematic wave number and Fo is the Froude number. The kinematic wave approximation was reasonably accurate except at the channel boundaries and for small values of KF02(less than or equal to 1). The accuracy of these approximations was significantly influenced by the downstream boundary, both in terms of the magnitude of the error and the segment of the channel reach for which these approximations would be applicable. (C) 1998 John Wiley & Sons, Ltd.