A tile drain is laid below a cropped land to remove excess irrigation water, the drainage coefficient of this drain is usually expressed as:

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Question

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JKSSB JE CE 2021 Official Paper Shift 3 (Held on 27 Oct 2021)

Answer 1

Concept:

Tile drains or underdrains

They are located at suitable depths below the ground surface above the impervious soil (clay) which prevents natural percolation of water and is usually covered with coarse sand or bajri.
They are preferably placed in the soil of medium or high permeability.
The Tile drains permit deep root development by lowering the water table.
Tile drains have their outlets in natural as well as artificial channels.
Gravitational water at the head of the tile drain is under pressure due to the head of water above it.

Drainage coefficient

Drainage coefficient is the rate at which water is removed by a drain.
It is expressed as the depth of water in cms or meters to be removed in 24 hours from the drainage area.
It depends on rainfall, type of soil, type of crop, degree of surface drainage, etc.
Its recommended value is 1 % of the average annual rainfall to be removed per day.