Friday, 22 June 2018

Types Of Irrigation || Irrigation Engineering

Types Of Irrigation

 (1) Surface irrigation
 (2) Subsurface irrigation
Types Of Irrigation

(1) Surface irrigation

Surface irrigation is defined as the group of water application procedures where water is applied and dispersed over the soil surface either by gravity or by pumping.

This technique is most appropriate to soils with low to moderate-infiltration capacities to lands  with comparatively uniform landscape (slopes less than 3%)
In India  ,More than seventy five percent (75%) of irrigated lands is supplied water by surface irrigation methods.

Surface irrigation can be further classified into : 
(i) Flow irrigation .
(ii) Lift irrigation.

(i)Flow irrigation:

 If the water is available at a higher level, and if it is supplied to lower level, by the mere action of gravity ,then it's known as Flow Irrigation.

(ii)Lift irrigation:

 If the water is lifted up by some mechanical or manual means, such as by pumps, etc. and then supplied for irrigation; then it's known as Lift irrigation . Utilization of wells and tubewells for providing  irrigation water fall under this category.

Flow irrigation further divided into the following two types:
(a) Perennial irrigation (b) Flood irrigation.

(a) Perennial Irrigation:

 ⇛In perennial system of irrigation, consistent and persistent water supply is  assured  to the crops as per the requirements of the crop, throughout the crop period.

In this system of irrigation, water is supplied through canal distribution system taking-off from above a weir or a reservoir.

When irrigation is done by diverting the river runoff into the main canal by constructing a diversion weir or a barrage across the river, then it is called as direct irrigation. But if a dam is built across a river to store water during monsoons, so as to supply water in the off-taking channel during periods of low flow, then it is termed as storage irrigation.

(b) Flood Irrigation:

In this types of  irrigation method , soil is kept submerged and fully flooded with water, so as to cause thorough saturation of the land.

It is commonly practiced in delta regions wherever the stream water level during flood is sufficiently high to provide water to the land by flow, or partly by flow and partly by lift.

This method of irrigation is also known as uncontrolled irrigation or inundation irrigation.

(2) Sub-surface Irrigation:

 In this kind of irrigation system, water does not actually wet the soil surface rather it flows underground and nourishes the plant roots by capillarity .
Sub-Surface irrigation can be further classified into  (i) Natural sub-irrigation (ii) Artificial sub-irrigation..

(i) Natural sub-irrigation:

Leakage water from channels, is going underground and all through passage via the sub-soil, it can irrigate crops, sown on lower lands, via capillarity. Sometimes leakage causes the water-. Table to rise up, which facilitates in irrigation of crops by capillarity. 

When underground irrigation is achieved, absolutely via natural processes without any additional more efforts, it is referred to as  natural sub-irrigation.

(ii) Artificial sub-irrigation:

  • When a system of open jointed drains is artificially laid below the soil, so as to supply water to the crops  with the aid of capillarity, then it is known as artificial sub-irrigation. It is a very costly method and for this reason, followed on a totally small scale. 

  This method may be adopted only in some special cases with favourable soil conditions and for cash crops of very excessive return.