Updated: Aug 28, 2019
Though irrigation is an age old science, the discovery and evolution of lift irrigation is recent compared to many other life changing discoveries by human beings. Lift irrigation is being used so commonly in our lives that it might be very hard to believe that in Maharashtra, lift irrigation was introduced in 1960s. Irrigation is a systematic way of providing water to crop in stipulated amounts at regular pre-determined time intervals.
Irrigation is essential to grow crops, vegetables, maintain landscapes etc. throughout the year. Irrigation is a must, especially in dry areas with less than average rainfall. It would not be an exaggeration if one says irrigation is the lifeline of agriculture in any country.
Areas which are topographically located below the water level, irrigation can be driven by the force of gravity itself. Such gravity based irrigation is less labor intensive and financially lean as well. If a region is located above the water level, carrying water to that region by the force of gravity is not possible. Lift irrigation is the only way of getting such regions under irrigation. In lift irrigation, water from the nearby source is lifted using pumps and then distributed to the crop. This method of lifting water using pumping installations and then supplying it to the land is called as lift irrigation.
In this article, we will first have a closer look at irrigation in general and then at lift irrigation.
Why do we need an irrigation system?
Though the nature works on its inherent laws and time frames, a certain factor of uncertainty is always associated with natural phenomena like rain. Rainfall varies not only in its quantity but also in terms of the duration. Due to the topological diversity, some regions receive rainfall much below the average. At such such locations, quantity of rainfall is so meager that they become unsuitable for human habitation for the entire or part of the year.
In such regions, irrigation primarily helps in two manners:
Making water available in the seasons when it is required.
Enabling proper and efficient usage of water which is stored during the rainy season or available from a nearby source.
Irrigation brings in a certainty factor to the availability of water for farming as well as for feeding it to the cattle and live stalk on the farm. As the farmers are moving a step further and planting vegetables and herbs which are not native, irrigation ensures that certain climatic conditions (e.g. moisture) which are essential for the growth of these plants are maintained. In the areas which have proper climatic conditions, farmers can raise two or more crops, which might also include cash crops per year. Irrigation can be effectively used even to fight famines.
Commonly used types of irrigation
Based on how and where the water is delivered, irrigation systems can be classified in 7 commonly used types.
Surface irrigation: In the surface irrigation, water is carried to the crops totally by the gravity and is disturbed across the land surface.
Localized irrigation: This system supplies water to the root zone, which makes it a more efficient irrigation system.
Manual Irrigation: Manual irrigation involves human labor to supply water to the crop in adequate quantity at regular time intervals.
Drip irrigation: Drip irrigation is the most efficient way of irrigation known. This system ensures that water is supplied directly to the roots of the plants and hence, provides maximum benefits with minimum water utilization.
Sprinkler based irrigation: This system makes use of sprinklers which cover a specific radius and sprinkle water onto the crop located in that region. This system can achieve a maximum of 90% efficiency.
Center Pivot and Lateral Move irrigation: These systems work on the gravity and deliver water to the crop or pastures through an overhead canopy.
Sub irrigation: This is an underground mode of irrigation in which water is distributed beneath the ground and absorbed up by the soil and reaches the plant roots.
What is Lift Irrigation?
Lift irrigation is a mode of irrigation which involves transporting water against the gravity with the help of pumps or surge pools and transported to the location where it is to be used. As mentioned earlier, lift irrigation is comparatively newer form of irrigation and has been introduced in Maharashtra after 1960s.
Since lift irrigation can be adapted at locations which are topographically disadvantaged, government has been aggressively promoting lift irrigation through various schemes. This has enabled farmers to use water from nearby rivers and streams round the year for farming.
Constructing dams and canals is beneficial only to the locations which fall below the water level. For the regions which are above the water level, list irrigation has acted as a boon. In lift irrigation, water is carried from a lower level to a higher level using pumps or other pumping mechanisms. In the state of Maharashtra, a significant portion of irrigated area deploys lift irrigation.
A general irrigation system is combined of two main functionalities:
1. A pumping mechanism to carry the water to a chamber which is located at elevation higher than the land which is to be irrigated.
2. A distribution mechanism which will properly distribute this water to the crop planted in the land. This distribution happens purely by the force of gravity.
Out of these two functionalities, it is comparatively easy to lift the water as it primarily involves selection of right number of pumps of right pumping capacity. The second part is much more complex. Many times, the region which is irrigated comprises of multiple regions located at different distances and at different elevations. Each region will also vary in terms of its size and water requirement. These factors make designing the distribution system a challenging task.
There are two methods which are most commonly used for the distribution of water which is lifted using pumps:
Topography based division: In this method, the topography and land contours are studied thoroughly and the complete area under irrigation is divided in individual blocks. Water requirement for each block is found out. Once we know the available head for that block and its water requirement, pipelines of appropriate sizes are designed. Each block will have its delivery chamber which will have necessary valves and other interlocks in place to control the flow to that particular block. In-spite of detailed study of the terrain and meticulously designed piping, a slight amount of variation exists in the availability of water to different blocks.
2. Equal division: In this method, the area under irrigation is divided in three or four equal parts and each part is given the entire amount of water for one day. This will ensure that every region gets full discharge once in every 3 or 4 days.
Though this method sounds much simpler when compared with the former, ensuring equal water distribution is an equally challenging task even in case of this systems and many alternate models have been proposed.
In the next part of this article, we will have a look at different components of a lift irrigation system and some insights into the actual designing of these systems.
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