Irrigation Systems in India
Irrigation is the replacement or supplementation of rainwater with another source of water. The main idea behind irrigation systems is that your crops and plants are maintained with the minimum amount of water required.
Water is a fragile natural resource and we have to incorporate methods to conserve it and not over-use it. The implementation of an irrigation system will help conserve water, while saving you time, money, preventing weed growth and increasing the growth rate of your lawns, plants, crops and flowers.
All the different sources of irrigation in India are divided into two major divisions; viz.
A Flow irrigation.
The water of a reservoir or tank usually remains at a higher level, and when a channel is connected to it, water automatically flows down the channel which serves the purpose of a canal for irrigating the land. In this case the water level remains higher than the fields. Such irrigation is known as the flow irrigation and it is generally possible in the plain areas.
B Lift Irrigation
But where the farm lands lie at a higher level and the canals or tanks lie at a lower level, it becomes necessary to lift the water by pump etc. to irrigate land. Water is lifted from wells and tanks by a crude country method (by tend) and from tube-wells by pumps for irrigation.
Nowadays the ground water is used for irrigation by lifting it by means of electric or diesel pump sets. Water is also lifted from wells tanks or rivers by pumps and irrigation is done through channels. This method of irrigation is known as the Lift Irrigation. Now a day’s sprinkle irrigation is being very much popular as more land can be irrigated with less water in this method.
The Irrigation Projects of India are classified into three types according to their capacity of irrigation.
They are (i) Major Irrigation Projects, (ii) Medium Irrigation Projects and (iii) Minor Irrigation Projects.
Irrigations in India carried are on in three different ways according to their sources, such as (i) by canals, (ii) by wells, and (iii) by tanks. Out of the total area under irrigation, 40 per cent are irrigated by canals, 40 per cent by wells and 12 per cent by tanks. The rest 8 per cent of land are irrigated by other methods.
1. Irrigation by Canals: This is the most convenient method of irrigation. About half of the total area under irrigation by canals is situated in Punjab, Haryana, Uttar Pradesh and Andhra Pradesh. It is easy to dig canals in these areas since the land is level and soil soft.
There are two types of canals; such as: perennial canals and inundation canals. Artificial reservoirs are created by constructing annicuts. Barrages or dams across rivers for perennial canals. Irrigation is being done in the Mahanadi delta area by constructing barrages at Naraj and at Jobra of Cuttack city across the Mahanadi and at Choudwar across the river Birupu.
When there is excessive flow of water in the rivers in flood, the extra water flows in the canals rising from those rivers. Such canals are effective only during floods; hence those are known as the inundation canals. This type of canal is very few in number in the country, more in Punjab than elsewhere.
There are many perennial canals in different regions of the country and the most famous of those are the Upper Bari Doab Canal and the Sir hind Canal in Punjab, the West Yamuna Canal and the Chakra Canal in Haryana. The Chakra Canal is the largest canal of the country. This canal serves the purpose of irrigation in the states of Punjab and Haryana. The Rajasthan Canal (The Indira Gandhi Canal) of Rajasthan is the longest canal of Asia. The northwestern part of Rajasthan is being irrigated by it. The other important canals are the Shard Canal, the Beta Canal, the Upper Ganga and the Lower Ganga Canals of Uttar- Pradesh.
Many canals have been dug out of the rivers Krishna, Godavari und Tungabhadra of Andhra Pradesh. The other important canals are the Son Canal of Bihar, the Damodar Canal of West Bengal, the Mahanadi and the Rushikulya Canals of Orissa, the Mettur and the Periyar Canals of Tamilnadu. The Krishnarajsagar, the Tungabhadra and the Ghataprava Canals of Karnataka.
2. Irrigation by Wells: The rain-water sinks down easily in the areas where the soil is soft and porous. So water is available at a lower depth when wells are dug and it helps irrigation. Primarily irrigation is carried on by wells in the western part of Uttar Pradesh, some parts of Bihar and in the blank cotton soil area of the Deccan.
In addition to it, in the coastal strip of Tamilnadu and Andhra Pradesh, some parts of Rajasthan, Haryana and Gujarat irrigation is also carried on by wells. Some or the other type of lift irrigation is required-for using the well-water for irrigation. Old methods like inot or ieiida are still practiced in many areas.
Power-driven pumps have become very popular in most parts. In some areas cattle or camels are used to lift water by the Persian wheels. The power-driven (electric or diesel) pumps can also lift water from a much greater depth from tube-wells. Now a days wind mills also lift water from the wells for irrigation purpose.
Irrigation by wells is more expensive, so more profitable farming of vegetables is carried on in those areas.
3. Irrigation by Tanks: Tank irrigation is the most feasible and widely practiced method of irrigation all over the Peninsula, where most of the tanks are small in size and built by individuals or groups of farmers by raising bonds across seasonal streams.
The soil of this plateau is hard and stony and its land is undulated and so, it is not easy to dig canals or wells in those areas. There are big tanks which have been created by raising high bonds on one side of the valley of hills. Small channels are dug out of both the sides of the tanks to irrigate lands. There are big reservoirs like Nizam Sagar, Usman Sagar, Hossain Sagar, Krishna raj Sagar etc. in the peninsular India. Besides, in rural areas of the Peninsula there are large numbers of small tanks for irrigation, but such tanks dry up during acute drought period and don’t help in irrigation.
4 Ditch Irrigation Ditch Irrigation is a rather traditional method, where ditches are dug out and seedlings are planted in rows. The plantings are watered by placing canals or furrows in between the rows of plants. Siphon tubes are used to move the water from the main ditch to the canals. This system of irrigation was once very popular in the USA, but most have been replaced with modern systems.
5 Terraced Irrigation This is a very labor-intensive method of irrigation where the land is cut into steps and supported by retaining walls. The flat areas are used for planting and the idea is that the water flows down each step, while watering each plot. This allows steep land to be used for planting crops.
The suitability of the various irrigation methods, i.e. sprinkler or drip irrigation, depends mainly on the following factors:
- natural conditions
- type of crop
- type of technology
- previous experience with irrigation
- required labour inputs
- costs and benefits.
NATURAL CONDITIONS The natural conditions such as soil type, slope, climate, water quality and availability, have the following impact on the choice of an irrigation method:
Soil type : Sandy soils have a low water storage capacity and a high infiltration rate. They therefore need frequent but small irrigation applications, in particular when the sandy soil is also shallow. Under these circumstances, sprinkler or drip irrigation are more suitable than surface irrigation. On loam or clay soils all three irrigation methods can be used, but surface irrigation is more commonly found. Clay soils with low infiltration rates are ideally suited to surface irrigation.
When a variety of different soil types is found within one irrigation scheme, sprinkler or drip irrigation are recommended as they will ensure a more even water distribution.
Slope: Sprinkler or drip irrigation are preferred above surface irrigation on steeper or unevenly sloping lands as they require little or no land levelling. An exception is rice grown on terraces on sloping lands.
Climate: Strong wind can disturb the spraying of water from sprinklers. Under very windy conditions, drip or surface irrigation methods are preferred. In areas of supplementary irrigation, sprinkler or drip irrigation may be more suitable than surface irrigation because of their flexibility and adaptability to varying irrigation demands on the farm.
Water availability: Water application efficiency (see Annex 4, step 8) is generally higher with sprinkler and drip irrigation than surface irrigation and so these methods are preferred when water is in short supply. However, it must be remembered that efficiency is just as much a function of the irrigator as the method used.
Water quality:Surface irrigation is preferred if the irrigation water contains much sediment. The sediments may clog the drip or sprinkler irrigation systems.
If the irrigation water contains dissolved salts, drip irrigation is particularly suitable, as less water is applied to the soil than with surface methods.
Sprinkler systems are more efficient that surface irrigation methods in leaching out salts.
TYPE OF CROP Surface irrigation can be used for all types of crops. Sprinkler and drip irrigation, because of their high capital investment per hectare, are mostly used for high value cash crops, such as vegetables and fruit trees. They are seldom used for the lower value staple crops.
Drip irrigation is suited to irrigating individual plants or trees or row crops such as vegetables and sugarcane. It is not suitable for close growing crops (e.g. rice).
6 Drip Irrigation This is known as the most water efficient method of irrigation. Water drops right near the root zone of a plant in a dripping motion. If the system is installed properly you can steadily reduce the loss of water through evaporation and runoff.
7 Sprinkler System This is an irrigation system based on overhead sprinklers, sprays or guns, installed on permanent risers. You can also have the system buried underground and the sprinklers rise up when water pressure rises, which is a popular irrigation system for use on golf courses and parks.
Advantages of sprinkler irrigation
- Elimination of the channels for conveyance, therefore no conveyance loss
- Suitable to all types of soil except heavy clay
- Suitable for irrigating crops where the plant population per unit area is very high. It is most suitable for oil seeds and other cereal and vegetable crops
- Water saving
- Closer control of water application convenient for giving light and frequent irrigation and higher water application efficiency
- Increase in yield
- Mobility of system
- May also be used for undulating area
- Saves land as no bunds etc. are required
- Influences greater conducive micro-climate
- Areas located at a higher elevation than the source can be irrigated
- Possibility of using soluble fertilizers and chemicals
- Less problem of clogging of sprinkler nozzles due to sediment laden water
8 Rotary System This method of irrigation is best suited for larger areas, for the sprinklers can reach distances of up to 100 feet. The word “Rotary” is indicative of the mechanical driven sprinklers moving in a circular motion, hence reaching greater distances. This system waters a larger area with small amounts of water over a longer period of time.
9 Center Pivot Irrigation This is a form of overhead irrigation. Steel or aluminum pipes are joined together, supported by trusses, mounted on wheeled towers. The sprinklers are situated on the length of the tower and they move in a circular motion.
Irrigation can lead to a number of problems:
- Competition for surface water rights.
- Overdrafting (depletion) of underground aquifers.
- Ground subsidence
- Underirrigation or irrigation giving only just enough water for the plant (e.g. in drip line irrigation) gives poor soil salinity control which leads to increased soil salinity with consequent build up of toxic salts on soil surface in areas with high evaporation. This requires either leaching to remove these salts and a method of drainage to carry the salts away. When using drip lines, the leaching is best done regularly at certain intervals (with only a slight excess of water), so that the salt is flushed back under the plant’s roots.
- Overirrigation because of poor distribution uniformity or management wastes water, chemicals, and may lead to water pollution.
- Deep drainage (from over-irrigation) may result in rising water tables which in some instances will lead to problems of irrigation salinity requiring watertable control by some form of subsurface land drainage.
- Irrigation with saline or high-sodium water may damage soil structure owing to the formation of alkaline soil