INTRODUCTION #
India is a Tropical country with varieties of climate, topography and vegetation. We have an agrarian economy and many resources depend on the agricultural output. For maximum crop productivity it is very essential to supply the optimum quantity of irrigation water at proper timings. Irrigation water performs number of important function, e.g. acts as nutrient and moisture carrier, ensures better utiliza- tion of chemical fertilizer, and maintains optimum temperature around plant environment.
Irrigation is necessary for the following reasons:
- Scanty Rainfall
- Non-Uniform Rainfall
- Increasing Yield in Dry Farming
- To Practice Crop Rotation
- Controlled Water supply
- To wash out or dilutes salts in soil
- To cool the soil and also the atmosphere and makes more favourable environment for healthy plant growth
Problems with excessive irrigation #
The excessive irrigation and unscientific use of irrigation water may give rise to the following ill effects. The states like Punjab are experiencing ill effects of excessive irrigation as part of the state is facing very deep water table problem and another part is facing problem of salinity. Proper management of water is necessary for good natural resource management and sustainable yield. The
disadvantages of excessive irrigation may be listed as follows:
- Wasteful use of water
- Water logging
- Soil degradation in irrigated areas
- Contamination of water with harmful sub- stances
- Damp climate and Ecological imbalances
- Mosquitoes breeding.
TYPES OF IRRIGATION #
Conventional and recognized means of irrigation are tanks, wells and canals.
Wells: Well irrigation is an important type of irrigation in India. Wells are particularly suitable for small farms. The important well-irrigated States are Uttar Pradesh, Punjab, Tamil Nadu and Maharashtra. In these States water-table is high, soil is soft and, therefore, wells are easily sunk.
- Tubewells are an important development in India. They are worked by electricity or diesel oil and thus, they relieve our cattle of much of the strain. They are being quickly developed in Uttar Pradesh, Bihar, Haryana and Punjab. This is because these have ample sub-soil water.
- Wells and tubewells account for about 48 percent of the total irrigation in India.
Tanks: Tanks are also an important and ancient source of irrigation. They are of considerable impor- tance in central and southern India, especially in
Andhra Pradesh and Tamil Nadu. About 8 percent of the total irrigated area is irrigated by tanks.
Canals: Canals are the most important means of irrigation in the country. Some canals were constructed by the early Hindu and Mohammedan kings. Most of the canals, however, are the product of the British rule. At present, canals irrigate about 39 percent of total irrigated area of India. Most of the canals of the country are found in Uttar Pradesh and Punjab. Storage canals have been constructed in Deccan and Madhya Pradesh.
- Sources of irrigation water are either surface water direct or stored or ground water to be tapped through bored wells using pumping system.
- Modern Irrigation may broadly be classified into Surface Irrigation and Sub-surface irri- gation.
Surface Irrigation #
In this type of irrigation water wets the soil surface. It can be further classified into:
Flow Irrigation #
When water is supplied from higher level to lower level by the action of gravity then it is called flow irrigation. The irrigation from canal water or river water is the example of flow irrigation.
Flow irrigation can be further subdivided into:
- Perennial irrigation
- Flood irrigation
Perennial Irrigation #
In this type of irrigation system, the water requirement for irrigation is supplied constantly and continuously in accordance with crop requirements throughout the crop period. In this system of irri- gation, water is supplied through the storage canal head works and canal distribution system.
Perennial canal system may be further sub-di- vided as follows:
- Direct Irrigation: When irrigation is done from direct run off of a river, or by divert- ing the river run off water into some canal by constructing a diversion weir or barrage
across the river. For example, Ganga Irriga- tion canal system.
- Storage Irrigation: When a dam is con- structed across a river to store water during the monsoon and the stored water is supplied in the off taking channels during periods of low flow, it is called storage irrigation. For example, Ram Ganga dam project in UP. In coastal areas where rivers are not perennial, storage irrigation becomes a necessity. How- ever, it is more costly and difficult to con- struct.
Flood Irrigation #
This kind of irrigation is sometimes called as Inundation irrigation. In this method of irrigation soil is kept submerged and flooded with water, so as to cause thorough saturation of the land.
Lift Irrigation #
When water is lifted up by any manual or mechanical means such as Persian wheel, pumps, etc. and then supplied for irrigation then it is called lift irrigation.
Localized irrigation #
Drip Irrigation #
Drip Irrigation also known as trickle irrigation, functions as its name suggests. In this system water- falls drop by drop just at the position of roots. Water is delivered at or near the root zone of plants, drop by drop. This method can be the most water-efficient method of irrigation, if managed properly, since evaporation and runoff are minimized.
The drip irrigation system is particularly suited to areas where water quality is marginal, land is steeply sloping or undulating and of poor quality, where water or labour are expensive, or where high value crops require frequent water applications. It is more economical for orchard crops than for other crops and vegetables since in the orchards plants as well as rows are widely spaced. Drip irrigation limits the water supplied for consumptive use of plants. By maintaining a minimum soil moisture in the root zone, thereby maximizing the water saving.
A unique feature of drip irrigation is its excellent adaptability to saline water. Since the frequency of
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irrigation is quite high, the plant base always remains wet which keeps the salt concentration in the plant zone below the critical. Irrigation efficiency of a drip irrigation system is more than 90 percent. Drip irrigation usage in India is expanding rapidly. In modern agriculture, drip irrigation is often combined with plastic mulch, further reducing evaporation, and is also the means of delivery of fertilizer.
The process is known as fertigation. Fertigation is the application of fertilizers, soil amendments, or other water-soluble products through an irrigation system. In this system fertilizer solution is distrib- uted evenly in irrigation. The availability of nutrients is very high therefore the efficiency is more.
Benefits of fertigation #
- Increased nutrient absorption by plants
- Reduction in fertilizer and chemicals needed
- Reduced leaching to the water table
- Reduction in water usage due to the plant’s resulting increased root mass’s ability to trap and hold water
- Application of nutrients at the precise time when they are needed and at the rate they are utilized.
Disadvantages of Fertigation #
- Concentration of solution decreases as fertilizer dissolves, leading to poor nutrient placement
- Results in pressure loss in main irrigation line
- Limited capacity
- Use of chemical fertilizers of low-sustainabil- ity, instead of organic fertilizers.
- Dependent on water supply’s non restriction by drought rationing.
Sprinkler System #
In sprinkler or overhead irrigation, water is piped to one or more central locations within the field and distributed by overhead high-pressure sprinklers or guns. The pump unit is usually a centrifugal pump which takes water from a source and provides ade- quate pressure for delivery into the pipe system.
Sprinkler irrigation has high efficiency. It how- ever, varies according to climatic conditions; 60%
in warm climate; 70% in moderate climate and 80% in humid or cool climate. Sprinklers are, however, not suitable for soils which easily form a crust. The water that is pumped through the pump pipe sprin- kler system must be free of suspended sediments
Sub-surface Irrigation #
In this type of irrigation, water does not wet the soil surface.
In this system of irrigation the supplied water comes directly in touch with root zone of the crops. This system of irrigation may be employed usefully under the following conditions:
- Topography conditions of area are uniform.
- Land slope is moderate.
- The quality of irrigation water is good.
- The soil in the roof zone is permeable in nature.
Sub surface irrigation may be classified into two types.
Natural Sub-irrigation #
When underground irrigation can be achieved simply by natural processes without any extra efforts it is called natural sub-Irrigation. In fact leakage water from channel, etc. goes underground and during seepage through the sub soil, it may irrigate the crop in the lower lands.
Artificial Sub-irrigation #
The open jointed system of drain is artificially laid below the soil so as to supply the water to the crop by capillary action, and then it is known as artificial sub-irrigation. This process is not adopted in India because it is very costly.
IRRIGATION PROJECTS #
Major, Medium and Minor Irrigation Projects #
The methods of irrigation used in India can be broadly classified into major, medium and minor irrigation schemes. Irrigation projects having Cultu- rable Command Area (CCA) of more than 10,000 hectares each are classified as major projects. Those having a CCA between 2,000 hectares and 10,000 hectares fall under the category of medium irrigation projects. And the projects which have a CCA of less
than 2,000 hectares are classified as minor irrigation schemes.
For the purpose of analysis the major and the medium irrigation projects are generally grouped together. These projects comprises a network of dams, bunds, canals and other such schemes. Such projects require substantial financial outlay and are, therefore, constructed by the government or any other agency which may draw financial assistance from the government and financial institutions.
The minor irrigation projects, on the other hand, comprise all ground water development schemes such as dug wells, private shallow tube wells, deep public tube wells, and boring and deepening of dug wells, and small surface water development works such as storage tanks, lift irrigation projects, etc. Minor irrigation projects or the groundwater development schemes are essentially people’s programmes imple- mented primarily through individual and cooperative efforts with finances obtained mainly through insti- tutional sources.
IRRIGATION THRUST IN BUDGET #
- Emphasis on completion of AIBP Projects.
- The government intends putting all the 89 ‘active’ irrigation projects under the Accel- erated Irrigation Benefit Programme (AIBP) on fast track.
Accelerated Irrigation Benefits Programme (AIBP) #
Government, in 1996-97, launched AIBP to provide Central Loan Assistance (CLA) to major/ medium/minor irrigation projects in the country.
The objective was to accelerate the implementa- tion of those projects which were beyond resource capability of the states or were in advanced stage of completion.
Only 143 of the 297 major projects approved have been completed.
It also aims to raise the required Rs 86,500 crore to finance these both through budgetary and extra-budgetary resources including taking the mar- ket route to raise funds.
The government has promised to complete at
least 23 of the 89 projects including a few on which work had started in the mid-1970s, before the end of March 2017. Another 23, that will form phase II, are expected to be completed by 2020.
Status of AIBP projects #
- Only 143 of the 297 major projects approved have been completed.
- 89 of them are in different stages of construc- tion which will be put on fast track.
- The remaining 65, which are yet to start, are likely to be reviewed to assess whether it would be feasible to go ahead with them at all.
Reasons for delay #
- AIBP suffered from inadequate central fund- ing.
- Its scope expanded to include more and more projects.
- There were time and cost overruns in most of the projects.
Other measures #
- Creation of a dedicated irrigation fund under the National Bank for Agriculture and Rural Development (NABARD), which has been asked to issue tax free bonds to borrow money.
- An initial corpus of Rs 20,000 crore has already been set up through the budget, which NABARD can leverage to mobilize further money from the market.
- The government has also asked the Central Water Commission and other agencies to take up 50 out of the 143 completed AIBP projects each year and work towards increasing their efficiencies.
- Each of these projects would now also have water user associations that will decide on how the water is distributed to every claimant in the area.
- Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) is also focusing on improving irrigation facilities.
