THE INTRODUCTION OF RUNOFF ROUTING INTO LARGE-SCALE HYDROLOGICAL MODELS

Two alternative schemes are presented that are appropriate for the rep resentation of runoff routing in large-scale grid-based hydrological m odels and atmospheric general circulation models (AGCMs). The first sc heme characterizes routing processes as a single conceptual store. The second scheme, developed by Naden (1992), uses the normalized network width function to characterize the channel network form and a linear solution to the convective diffusion equation of one-dimensional flow to characterize the routing effect of a single channel. Both schemes a re applied to the Severn catchment at the daily time-scale for the per iod 1981 to 1990 using a grid resolution of 40 km. Comparable results were obtained using both schemes (efficiencies were of the order of 80 % in both cases). A combined model using a conceptual reservoir to rep resent hillslope routing and the network-based scheme to represent cha nnel routing was developed to investigate the relative roles of hillsl ope and channel routing at the catchment scale. The application of thi s model demonstrated the important role of hillslope routing in reprod ucing the low frequency component of the catchment response. However, in terms of goodness-of-fit there was little to choose between the thr ee schemes. Consequently, it is recommended that additional a priori k nowledge of the routing processes should be used to condition the choi ce of model structure. (C) 1997 John Wiley & Sons, Ltd.