This text is based on the chapter on interception in the monograph on evaporation by Schrödter (1985)

Interception is the rainfall intercepted by leaves and vegetation:

with = precipitation, = throughfall, = stem flow and = interception.

The interception reduces precipitation to the effective precipitation and represents the difference between precipitation and effective precipitation.

There are several formulae for calculating interception. The formula of Hoyningen-Huene (1980, 1983) is based on precipitation and leaf-area-index:

From the above formula the precipitation can be estimated at which the interception store is fully saturated:

where is a threshold precipitation.

We can also estimate the potential interception with:

As a rule of thumb and for rough estimates, the interception ranges from 8 % to 20% for humid regions and crops and can reach up to 30 % for dence vegetation.

Fix Python program

interception.py

from pylab import *
 
def interception(No, LAI):
    icm = 0.935+0.498*LAI-0.00575*LAI*LAI
    ic = -0.42+(0.245*No)+(0.2*LAI)+(0.0271*No*LAI)-(0.0111*No*No)-(0.0109*LAI*LAI)
    return ic
 
LAI = 3.0    
No = arange(0.0, 25.0, 1.0)
plot(No, interception(No,LAI))
xtext = xlabel('precipitation (mm/d)')
ytext = ylabel('Interception (mm)')
setp(xtext, size='medium', name='courier', weight='bold', color='g')
setp(ytext, size='medium', name='helvetica', weight='light', color='b')
show()