Runoff and their Types


Runoff, And Their Types

Definition:” It is that portion of rainfall, which makes its way towards streams, rivers etc. After satisfying the initial losses etc. is called as runoff.

Types of Runoff:
1. Surface runoff.
2. Sub – surface runoff, and
3. Base flow.

1. Surface Runoff: It is that portion of rainfall which enters the stream immediately after the rainfall. It occurs. When all losses are satisfied and if rain is still continued, with the rate greater than in filtration rate; at this stage the excess water makes a head over the ground surface (surface detention) which tends to move from one place to another, known as overland flow. As soon as the overland flow joins to the streams, channels or oceans, termed as surface runoff.

2. Sub – surface Runoff: That part of rainfall, which first leaches into the soil and moves laterally without joining the water – table to the Streams Rivers or oceans is known as sub – surface runoff. Sometimes sub – surface runoff is also aerated under service ninoff due to reason that it takes very title time to reach the river or channel in comparision to ground water. The sub – surface runoff is usually referred as interflow.

3. Base flow:  It is delays flow, defined as that part of rainfall which after talling on the ground surface in fill rated into the soil and meets so the water table and flow to the streams oceans etc. The movement of water in this type of runoff is very slow that is why it is also referred as delayed runoff. It takes a long time to join the rivers or oceans. Some times base flow is also known as ground water flow.
Total Runoff = Surface runoff + Base flow (Including sub – surface runoff)

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