Introduction to Runoff
Over
the land surface, for the generation of runoff, the primary source of water is
Rainfall. A part of rainfall that intercepted by the vegetation, buildings and
other objects and prevented to reach them on grand surface is called as
interception. Part of rainfall stored in the surface depressions which in due
course of time gets infiltrate or evaporated is referred as depression storage
[ Initial detention).
the land surface, for the generation of runoff, the primary source of water is
Rainfall. A part of rainfall that intercepted by the vegetation, buildings and
other objects and prevented to reach them on grand surface is called as
interception. Part of rainfall stored in the surface depressions which in due
course of time gets infiltrate or evaporated is referred as depression storage
[ Initial detention).
When these entire loses are satisfied then excess rainfall moves over land
surface is known as overland flow and draining the same into channel or stream
is termed as “Runoff”.
Definition:
Runoff:
Runoff
is that portion of the rainfall or irrigation water [or any other flow].
Applied which leaves a field either as surface or as subsurface flow.
is that portion of the rainfall or irrigation water [or any other flow].
Applied which leaves a field either as surface or as subsurface flow.
When
rainfall intensity reaching the soil surface is less than the infiltration
capacity, all the water is absorbed in to the soil. As rain continues
soil becomes saturated and infiltration capacity is reduced, shallow depression
begins to fill with water, then the over flow starts.
rainfall intensity reaching the soil surface is less than the infiltration
capacity, all the water is absorbed in to the soil. As rain continues
soil becomes saturated and infiltration capacity is reduced, shallow depression
begins to fill with water, then the over flow starts.
Surface detention/ Detention storage:
The
amount of water on the land surface in transit to words stream channels is
called detention storage/surface detention.
amount of water on the land surface in transit to words stream channels is
called detention storage/surface detention.
Surface Runoff:
The
runoff which travels over the ground surface to the channels of watershed
runoff which travels over the ground surface to the channels of watershed
Subsurface Runoff:
The
portion of unfiltered water which penetrated to shallow depth travels laterally
and is intercepted by channels.
portion of unfiltered water which penetrated to shallow depth travels laterally
and is intercepted by channels.
Runoff Cycle:
It
is that part of hydrological cycles which galls between the phase of
precipitation and its subsequent discharge in the stream channels or direct
return to the atmosphere through evaporation and evapotranspiration.
is that part of hydrological cycles which galls between the phase of
precipitation and its subsequent discharge in the stream channels or direct
return to the atmosphere through evaporation and evapotranspiration.
Conditions Associated With Runoff Cycle:
- This refers to the end of day
period and beginning of the intense and isolated storm. - It is the stage after beginning
of rainfall causes the overland flow, base flow, and development of channel
storage. - It refers to the condition
approaching the end of all isolated intense storm. - This is the stage indicating
after end of rainfall where rainfall causes the overland low, base plot
and development of channel storage.
Types of Runoff:
- Surface runoff
- Sub-surface runoff
- Base flow
a. Surface Runoff:
That
portion of rainfall which enters the stream immediately after the rainfall. It
occurs when all loses is satisfied and rainfall is still continued and rate of
rainfall [intensity] in greater than infiltration rate.
portion of rainfall which enters the stream immediately after the rainfall. It
occurs when all loses is satisfied and rainfall is still continued and rate of
rainfall [intensity] in greater than infiltration rate.
b. Sub-Surface Runoff:
That
part of rainfall which first leaches into the soil and moves laterally without
joining the water table, to the stream, rivers or ocean is known as sub-surface
runoff. It is usually referred is inter-flow.
part of rainfall which first leaches into the soil and moves laterally without
joining the water table, to the stream, rivers or ocean is known as sub-surface
runoff. It is usually referred is inter-flow.
c. Base flow:
It
is delayed flow defined as that part of rainfall, which after falling on the
ground the surface, infiltrated into the soil and meets to the water table and
flow the streams, ocean etc. The movement of water in this is very slow.
Therefore it is also referred a delayed runoff. Total runoff = Surface
runoff + Base flow (including subsurface runoff)
is delayed flow defined as that part of rainfall, which after falling on the
ground the surface, infiltrated into the soil and meets to the water table and
flow the streams, ocean etc. The movement of water in this is very slow.
Therefore it is also referred a delayed runoff. Total runoff = Surface
runoff + Base flow (including subsurface runoff)
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