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The Drainage Basin Hydrological Cycle
Key term
Precipitation
Evapotranspiration
Interception
Depression storage
Soil moisture
Baseflow or groundwater
flow
River channel
Percolation
Throughflow
Infiltration
Overland flow
Meaning
The type, the total amount and the intensity of precipitation
are key factors in determining the nature of water movement.
Prolonged or heavy rainfall is more likely to lead to flooding.
Snow acts as a store of water, which can lead to flooding when
it melts.
When the water loss from the ground surface to the
atmosphere (evaporation) combines with water given off from
plants (transpiration) to form the main output from the
system.
Vegetation, particularly trees, intercepts some precipitation on
its way to the ground. Water is then lost back into the
atmosphere by Evapotranspiration. The intercepting plants also
use some water for growth. Vegetation reduces and slows down
water transfer.
When water is stored temporarily on the ground surface in the
form of puddles.
The existing moisture in the soil is very important in
determining whether precipitation will be absorbed or be
forced to flow as overland flow. Clay soils can be very wet and
boggy (leading to overland flow) whereas sandy soils tend to
absorb more precipitation.
This is a very slow transfer of water through rocks. Only in
limestone areas, where there are extensive underground
channels, can the flow be faster.
The river is an important store of water. It also forms the
‘exit’ for water transferred through the drainage basin.
This is the deeper transfer of water into permeable rocks –
those with joints (pervious) or those that are porous.
This is the downhill transfer of water through the soil layer to
the river. This shallow transfer can be quite rapid in very
porous sandy soils.
This involves water moving from the ground surface into the
soil. The rate of infiltration (infiltration capacity) depends
upon the moisture content of the soil and its porosity (the
number of air spaces contained within it).
This is the rapid form of water transfer over the surface of
the ground. It is most likely to occur during heavy periods of
rainfall, or when the soil has completely saturated.