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The irrigation water can be distributed efficiently to the farms in various ways like free flooding, check flooding, border flooding, basin flooding, furrow irrigation method, drip, and sprinkler irrigation method. The type of technique chosen for the irrigation land depends on the soil texture, land contour, type of crop that is cultivated and the slope of the land.
The major techniques employed for distributing the irrigation water are explained briefly in this article.
1. Free Flooding Irrigation
The free flooding technique is performed by excavating ditches in the irrigation land. As shown in the figure, from the main supply ditch, water is collected in the subsidiary or lateral or contour ditches. These subsidiary ditches are excavated either along the contour or above or below the slope of the area. The water from the lateral ditches is allowed to flow freely without any sort of control and hence it is also called wild flooding.
The wild flooding technique is best suitable for crops or pastures that are cultivated closely. The contour ditches excavated in free flooding techniques are mostly spaced at a distance of 20 to 30m. This merely depends on the type of soil, type of crop, soil texture, etc. It performs well when employed on a sloped land or an irregular land. This method is not preferred where checks, basins, border or furrows are feasible.
The initial cost of land preparation of free flooding is very less. But it demands high labour requirements and possesses less efficiency.
2. Border Flooding Irrigation
Border flooding method involves dividing the irrigation land into several strips of width around 10 to 20 m and length of 100 to 400m. Each strip is separated by a border or levees. The ridges constructed between the borders must have sufficient height to prevent overtopping during the irrigation.
As shown in the figure-2, the water is allowed to flow from the supply ditch to each strip. So to prevent water to concentrate in one area, the surface must be leveled in the direction perpendicular to the flow of water. As the water flows through the strip, it infiltrates at the lower end. At this point, the supply is closed. High efficiency is gained when the strips are short and narrow.
3. Check Flooding
Check flooding is a method similar to flooding where the water is controlled by the surrounding check area that is formed by the construction of levees. These levees can be short or long which are constructed along the contour. Most of the check area has a measure varying from 0.2 to 0.8 hectares. In check flooding, the water from the supply ditch is allowed to move to the check area and is held for a period until desirable infiltration takes place.
Check flooding is suitable for both permeable and less permeable soil. If applied for permeable soils, the water is quickly spread to the soil. While in case of less permeable soil, the water is allowed to stay for longer period to ensure adequate penetration.
4. Basin Flooding
Basin flooding is a special type of check flooding as shown in figure-4. Here, the subsidiary ditches receive water from the mains supply ditch. Each subsidiary ditch is connected to a basin that occupies one or more trees. This method is especially followed for orchard trees.
5. Furrow Irrigation Method
In this method, furrows are made between rows of plants. Furrows are narrow field ditches that carry water with a length of 400 meters and a depth of 8 to 30cm. The spacing of crops decides the spacing of the furrows.
These are employed for row crops. Furrows can be made in corrugations for land areas with irregular topography. Excessive length of furrows must be avoided because long furrows may result in high water on one end and less water on the other end.
The water from the furrows is diverted to the row crops by means of plastic tube syphons or border takeout or spiles or lathe box.
6. Sprinkler Irrigation System
The sprinkler irrigation system is a farm-water application that applies water in the form of spray. This spraying is performed by a series of pipes and pumps. It is a kind of artificial rainfall and hence nourish the crops with the required amount of water.
The method is very costly and involves great technicalities. For examples, debris and silts must not enter these pipe system as it will affect the smooth operation of the sprinkler. Debris results in the choking of the nozzles while silt results in huge wear in the impellers, bearings and the nozzles.
7. Drip Irrigation Method
The drip irrigation method is also called trickle irrigation. In this system, the water is applied directly to the roots by an arrangement made underground. This hence results in the prevention of loss of water due to evaporation and percolation.
This is a modern irrigation water distribution technique employed in areas where there is a scarcity of water and the presence of salts in the available water.
The drip irrigation system consists of a head, mains, sub-mains, laterals and drop nozzles.
Also Read: Types of Irrigation