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Runoff Cycle

The document describes the four stages of the runoff cycle: Stage 1 refers to the end of a dry period with low stream flow supported only by groundwater. Stage 2 begins with rainfall but infiltration and storage prevent overland flow. Stage 3 occurs at the end of intense rainfall when storages are full and overland flow reaches its maximum. Stage 4 follows the end of rainfall as water evaporates and percolates from storages back underground.

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Kaushiki Kundu
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777 views1 page

Runoff Cycle

The document describes the four stages of the runoff cycle: Stage 1 refers to the end of a dry period with low stream flow supported only by groundwater. Stage 2 begins with rainfall but infiltration and storage prevent overland flow. Stage 3 occurs at the end of intense rainfall when storages are full and overland flow reaches its maximum. Stage 4 follows the end of rainfall as water evaporates and percolates from storages back underground.

Uploaded by

Kaushiki Kundu
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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Runoff Cycle:

It is a descriptive term used to denote that part of the hydrologic cycle, which falls between the
phase of precipitation and its subsequent discharge into the stream channels or direct return to the
atmosphere through evaporation and evapotranspiration.

There are following four critical stages, which are associated to the runoff cycle:

Stage 1:

This refers to the end of dry period and beginning of the intense and isolated storm. At this stage, all
surfaces and channel storages get depleted, except in reservoirs, lakes and ponds from the previous
storms. Under this condition the source of stream flow is only the ground water flow. The flow
decreases with time.

Stage 2:

It is the stage after beginning of rainfall and before saturation of interception and depression
storage. In this condition, whatever precipitation takes place, falls directly on the land surface or on
stream surface, known as channel precipitation; this provides an immediate increment in stream
flow. Most of the rain water, reaching the ground are either retained on the surface or passed into
the soil by infiltration.

Once it is infiltrated into the soil, it starts to replenish the soil moisture deficiency, without
contributing to the ground water. At this stage, the overland flow takes place only from those parts
of watershed which are in impervious nature such as roads etc., while from the soil surface it does
not occur, because rain water is consumed by several losses such as depression storage and
infiltration loss.

The evaporation and evapotranspiration in this stage are negligible or very less as compared to those
at fair weather conditions, which is because of high atmospheric humidity.

Stage 3:

This stage refers to the condition of end of an isolated intense storm. After a long period of conti-
nuous intense storm all losses such as interception by vegetative foliage and depression storages on
land surface are satisfied; and infiltration rate is reduced to the minimum, causing the overland flow
to reach at maximum level and becoming as one of the major sources of surface flow from entire
drainage basin to generate runoff. In addition, the sub-surface flow is also started and meets to the
stream flow.

Stage 4:

This is the stage indicating after end of the rainfall. In this stage the rainfall causes overland flow,
base flow and development of channel storage. A large amount of water is lost from soil storage,
interception and depression storage due to evaporation. In addition, the stored water in surface
depressions also starts to percolate down and meets to the water-table.

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