Geoscience Reference
In-Depth Information
B3.2.2 The Rutter Model
Perhaps the most widely used model of interception is that proposed by Jack Rutter (Rutter
et al. , 1971, 1975; Calder, 1977; Gash and Morton, 1978). A schematic diagram of the model
is shown in Figure B3.2.1.
The model is based on two storage components, one for canopy interception and one for
stemflow. Incoming precipitation is partitioned into direct throughfall that reaches the ground
without interacting with the canopy, input to the canopy interception and stemflow stores. The
partition coefficients, p and p t , shown in Figure B3.2.1 will be vegetation type and seasonally
dependent, but are often assumed constant in applications. Drainage from the stemflow store
begins when the minimum storage capacity is exceeded. For the canopy store, drainage takes
place at the rate:
D t = D s exp( b { S TF − C TF }
)
(B3.2.1)
where D s is the drainage rate when the storage depth S TF just equals the capacity C TF and b
is a coefficient. Note that, if applied in this form, the results are dependent on the time steps
used and it is better to integrate the equation over the required time step to calculate a storage
at the end of that time step, from which the integrated drainage may be obtained from the
change in storage. For the stemflow store, all storage in excess of the capacity C SF is assumed
to drain rapidly to the ground. The values of the storage minimum capacities C TF and C SF can
be determined by the type of regression analysis on storm volumes described above.
Rainfall Input, P
Evaporation
from Canopy
Evaporation
from Stems
S
C
TF
E = E p
TF
S
C
SF
E = p t E p
E = E p
SF
S TF
<
C TF
E = p t
E p
(1-p-p )
p t P
pP
t
S TF
>
C TF
S SF < C SF
S SF > C SF
S TF
C TF
D = D s exp(b{ S TF - C TF })
S SF
C SF
Throughfall
Stemflow
Figure B3.2.1 Schematic diagram of the Rutter interception model (after Rutter et al., 1971, with kind
permission of Elsevier).
 
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