Interception (hydrology)

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In hydrology, interception is understood as the interception or retention of precipitation on the "surface" of the vegetation. The term interception is mostly used for precipitation that comes down as rain , but it is also used for snow . In plant canopies the interzeptierten rainfall arrive either as stem flow or the throughfall to the ground or evaporate . Since the evaporating water is no longer available for the formation of new groundwater or for plant growth, the term interception loss has become commonplace. The loss of interception is of great importance for the water balance and the water cycle .

The interception capacity is the amount of precipitation that can accommodate a surface and hold back. When it starts to rain, hardly any water reaches the forest floor in a dense forest, as the surfaces of the leaves and needles are first wetted. With longer periods of precipitation or higher precipitation intensity, their interception capacity is finally exceeded and water drips onto the ground.

The loss of interception in coniferous forests amounts to 30–40% of the total annual precipitation. The interception losses are generally lower in deciduous forests at 15–25%; in non-leafy trees they are only 4–7%.

In tropical forests, interception losses are around 10–15% of annual precipitation. Although tropical forests are often very dense, the interception rates are below those of forests in temperate latitudes. There are three main reasons for this: Most precipitation events are of short duration, but of very high intensity, large drops do not wet the leaf surface as effectively as fine droplets (increases the permeability if the interception reservoir is not completely filled) and many leaves of the rainforest have the structural property to concentrate the leaf runoff.

Interception and loss of interception also occur when precipitation has fallen in the form of snow. Part of it can be released back into the atmosphere as water vapor through evaporation or sublimation . A quantitative estimate is particularly difficult here.

The interception evaporation in the plant world differs fundamentally from the transpiration : In both cases it is about the evaporation of water; in correspondence with the sweat secretion in humans and animals but also refers to the botanic transpiration that evaporation of water from the own organism comes. Interception evaporation, on the other hand, refers to the evaporation of water that has reached the plant from outside in the form of precipitation.

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  1. ↑ H. Brechtel (1990): Interception. In: A. Baumgartner, HJ Liebscher (Hrsg.): Textbook of Hydrology , Volume I (General Hydrology) , Borntraeger, Stuttgart
  2. ↑ a b R.C. Ward, M. Robinson (1989): Principles of Hydrology , 3rd ed., McGraw-Hill, Maidenhead, ISBN 0-07-707204-9
  3. ↑ a b R.C. Ward, M. Robinson (2000): Principles of Hydrology , 4th ed., McGraw-Hill, Maidenhead, ISBN 0-07-709502-2