Geoscience Reference
In-Depth Information
Figure 4.7
Final block diagram of the CI6 bilinear power law model used in the predictions of Figure 4.6
(after Young and Beven, 1994, with kind permission of Elsevier).
Figure 4.8
Observed and predicted discharges for the CI6 catchment at Llyn Briane, Wales, using the bilinear
power law model with n
=
0
.
628
(after Young and Beven, 1994, with kind permission of Elsevier).
variable as an input to the nonlinear effective rainfall filter component. As noted earlier, Young (2000),
in a second example of modelling daily discharges for one of the Coweeta catchments, also show that
temperature can be used as a surrogate variable to improve the accuracy of longer period simulations.
4.5 Physical Derivation of Transfer Functions
In Sections 4.3 and 4.4, the transfer functions have been fitted to the data using the generalised linear
model developed in Box 4.1. It is possible, however, to develop a transfer function based on the form of a
catchment, in a way similar to the Imbeaux/Ross time-area diagram interpretation of the unit hydrograph
introduced in Section 2.2. We consider two more recent types of transfer function based on catchment
form, one based on the network width function, the other on the geomorphological unit hydrograph
(GUH). Note, however, that both of these approaches address only the routing problem and not how
much of the rainfall to route. Thus, both require prior estimation of effective rainfalls but they can be
used with a variety of effective rainfall models, including those of Chapter 2 and the nonlinear filters
described earlier in this chapter. In this respect, they are in the classical unit hydrograph tradition.
