Irrigation water can be supplied to the land to be irrigated using one of the following methods:
(i) Surface irrigation methods which can be of the following types:
(a) Uncontrolled (or ‘free’ or ‘wild’) flooding method.
(b) Border strip method.
(c) Check method.
(d) Basin method.
(e) Furrow method.
(ii) Subsurface irrigation method.
(iii) Sprinkler irrigation method.
(iv) Drip (or ‘trickle’) irrigation method.
(i) Surface Irrigation Methods:
The history of irrigation begins with the application of water to the land in some kind of surface irrigation method. It is the oldest and most common method of irrigation. It, however, does not result in high levels of performance. In all the surface methods of irrigation, water is either ponded on the soil or allowed to flow continuously over the soil surface for the duration of irrigation.
(a) Uncontrolled Flooding:
In the uncontrolled flooding method of irrigation, water is applied to a field for irrigation without any land preparation and without any levees to guide or restrict the flow of water on the field. Water is simply admitted at one end of the field, thus, letting it flood the entire field without any control. This method generally results in excess irrigation at the inlet region of the field and insufficient irrigation at the outlet region.
This method has the advantage of low expenses on land preparation. Its main disadvantage is greater loss of water due to deep percolation and surface runoff. This method is, therefore, suitable when water is available in large quantities, the land surface is irregular, and the crop being grown is unaffected because of excess water.
(b) Border Strip Method:
It is a controlled surface irrigation method in which the farm is divided into a number of strips which are separated from each other by low levees (or ‘borders’ or ‘dikes’). These strips can be 3-20 m wide and 100-400 m long depending upon the unevenness of the land and the size of the supply channel.
However, narrow strips would require too many levees which would occupy lot of cultivable land. The length of the strip depends primarily on the infiltration rate of the soil and the slope of the land and is generally 60 to 120 m for more permeable sandy and sandy-loam soil and 150 to 300 m for less permeable clay loam and clay soils.
The strips do not have cross slopes but slope along the length depending upon the type of the soil. The strips should have much flatter longitudinal slope for less permeable clay and clay-loam soils, and flatter slope for more permeable sand and sandy-loam soils. Water from the supply channel is diverted to each of these strips along which it flows slowly towards the downstream end and, thus, irrigates the land.
(c) Check Method:
In this method, the land to be irrigated is divided into a number of almost levelled plots (kiaries) surrounded by levees. Water is admitted from the farmer’s field channels to these plots turn by turn so that the plots are flooded without overtopping the levees. Size of individual plots may vary from as small as one metre square (suitable for growing vegetables) to as large as one hectare or even more.
This method is suitable for wide range of soils ranging from very permeable to much less permeable soils. The farmer has good control over the distribution of water in different parts of his farm. The water application efficiency is higher for this method.
However, this method requires constant attendance for admitting and closing the supplies to the levelled plots. Also, there is some loss of cultivable area which is occupied by the levees. Sometimes, levees are made sufficiently wide to grow ‘row’ crops and, thus, compensate to some extent the loss of cultivable area on account of levees.
Answers & Comments
Irrigation water can be supplied to the land to be irrigated using one of the following methods:
(i) Surface irrigation methods which can be of the following types:
(a) Uncontrolled (or ‘free’ or ‘wild’) flooding method.
(b) Border strip method.
(c) Check method.
(d) Basin method.
(e) Furrow method.
(ii) Subsurface irrigation method.
(iii) Sprinkler irrigation method.
(iv) Drip (or ‘trickle’) irrigation method.
(i) Surface Irrigation Methods:
The history of irrigation begins with the application of water to the land in some kind of surface irrigation method. It is the oldest and most common method of irrigation. It, however, does not result in high levels of performance. In all the surface methods of irrigation, water is either ponded on the soil or allowed to flow continuously over the soil surface for the duration of irrigation.
(a) Uncontrolled Flooding:
In the uncontrolled flooding method of irrigation, water is applied to a field for irrigation without any land preparation and without any levees to guide or restrict the flow of water on the field. Water is simply admitted at one end of the field, thus, letting it flood the entire field without any control. This method generally results in excess irrigation at the inlet region of the field and insufficient irrigation at the outlet region.
This method has the advantage of low expenses on land preparation. Its main disadvantage is greater loss of water due to deep percolation and surface runoff. This method is, therefore, suitable when water is available in large quantities, the land surface is irregular, and the crop being grown is unaffected because of excess water.
(b) Border Strip Method:
It is a controlled surface irrigation method in which the farm is divided into a number of strips which are separated from each other by low levees (or ‘borders’ or ‘dikes’). These strips can be 3-20 m wide and 100-400 m long depending upon the unevenness of the land and the size of the supply channel.
However, narrow strips would require too many levees which would occupy lot of cultivable land. The length of the strip depends primarily on the infiltration rate of the soil and the slope of the land and is generally 60 to 120 m for more permeable sandy and sandy-loam soil and 150 to 300 m for less permeable clay loam and clay soils.
The strips do not have cross slopes but slope along the length depending upon the type of the soil. The strips should have much flatter longitudinal slope for less permeable clay and clay-loam soils, and flatter slope for more permeable sand and sandy-loam soils. Water from the supply channel is diverted to each of these strips along which it flows slowly towards the downstream end and, thus, irrigates the land.
(c) Check Method:
In this method, the land to be irrigated is divided into a number of almost levelled plots (kiaries) surrounded by levees. Water is admitted from the farmer’s field channels to these plots turn by turn so that the plots are flooded without overtopping the levees. Size of individual plots may vary from as small as one metre square (suitable for growing vegetables) to as large as one hectare or even more.
This method is suitable for wide range of soils ranging from very permeable to much less permeable soils. The farmer has good control over the distribution of water in different parts of his farm. The water application efficiency is higher for this method.
However, this method requires constant attendance for admitting and closing the supplies to the levelled plots. Also, there is some loss of cultivable area which is occupied by the levees. Sometimes, levees are made sufficiently wide to grow ‘row’ crops and, thus, compensate to some extent the loss of cultivable area on account of levees.