Comment on ‘‘Using numerical modelling to evaluate the capillary fringe groundwater ridging hypothesis of streamflow generation’’ by

Cloke et al. (2006) discuss an interesting topic of runoff generation, a central theme in hydrology. While their numerical experiment reproduced the physical experiment of Abdul and Gillham (1984) with good agreement, I feel that their proposed generalization of the model results to more realistic natural settings of riparian zones is not perfectly well supported. This is so because the stream channel initially is disconnected from the groundwater in Abdul and Gillham (1984) experiment which is replicated by Cloke et al. (2006) (Figs. 2, 4, and 6) in their above numerical study. In my opinion the initially disconnected stream setting ought to be replaced by a more common (at least in humid climates) perennially gaining stream example where groundwater is in continuous contact with the channel through the streamaquifer interface permitting immediate water fluxes across it when responding to precipitation. This more realistic boundary condition at the stream-aquifer interface will allow rapid groundwater inflow to the stream and should be