Introduction to Hydrology

The hydrological cycle of humid tropical forests
This section explains how the interaction between forest vegetation, soils
and atmosphere persists. This interaction process between various factors
in an ecosystem is called the hydrological cycle and based on this we can
gain insight in what will happen if a forest is converted to another type of
land use.
The hydrological cycle contains several factors, which influence the
cycle of water through a system. These factors are:
• Precipitation (rainfall)
• Interception by tree canopies, other vegetation or surface litter
• Throughfall and stemflow reaching the soil
2
Figure 1: Forest with epiphytes that
only thrive in moist air. (Source:
Hamilton and Bruijnzeel, 2000)l

• Infiltration or overland flow
• Evapotranspiration (evaporation
and transpiration)
Precipitation
Rain is the main precipitation input to
forests in the humid tropics. A small
part reaches the forest floor directly as
‘throughfall’ without touching the
canopy.
Interception
Of the rain that strikes the vegetation
a substantial portion is intercepted by
the canopy and evaporates back into
the atmosphere during and
immediately after the storm.