Different types of irrigation and irrigation systems storage

GS III: Different types of irrigation and irrigation systems storage

Introduction:

• Irrigation is the artificial application of water to the land or soil. It is the replacement or supplementation of rainwater with another source of water. It is used in dry areas and during periods of inadequate rainfall.
• The main idea behind irrigation systems is to:

1. Assist in the growing of agricultural crops and plants by maintaining with the minimum amount of water required.
2. maintenance of landscapes
3. Re-vegetation of disturbed soils.

Additionally, irrigation also has a few other uses in crop production, which include:

1. protecting plants against frost
2. suppressing weed growth in grain fields
3. preventing soil consolidation.
4. for dust suppression,
5. disposal of sewage, and in mining.
6. In contrast, agriculture that relies only on direct rainfall is referred to as rain-fed or dryland farming.
7. Irrigation is often studied together with drainage, which is the natural or artificial removal of surface and sub-surface water from a given area.

IRRIGATION IN INDIA: 

Water scenario is now fast changing as an outcome of increasing population, rising demand for irrigation to raise high-yielding varieties of crops, industrialization, electricity generation, rapid urbanization, the impact of global warming and erratic rainfall.

• India is home to 15% of the world’s population but has only 4% of the world’s freshwater resources.
• India has the largest irrigated area in the world, where about 85% of total irrigation potential (139.90 million hectares) has already been created.
• Currently, the agricultural sector consumes about 80% of the water in the country.
• Moreover, the country uses 2-3 times more water than major agricultural countries such as China, Brazil, and the USA to produce one unit of food crop.

Irrigation water may be applied to the crops in three basic methods that include surface irrigation, sprinkler irrigation and sub-surface irrigation method. Every irrigation method has advantages and disadvantages. Therefore before choosing a specific technique, the irrigation engineer must evaluate all the factors and choose method which is most suited for local condition (Dr. B. C. Punmia, 2009).

I. Surface Irrigation

Surface irrigation is the oldest form of irrigation techniques. In this technique, water is applied and distributed over the surface of soil by gravity, i.e., from an area of higher elevation to that of lower region in order to dampen and thereby infiltrate the soil. It is the most common form of irrigation throughout the world. This technique can be adopted after considering the following factors are which include the hydraulics of surface irrigation:

• Surface slope of the field
• Roughness of the field surface
• Depth of water to be applied
• Length of run and time required
• Size and shape of water course
• Discharge of water course
• Filed resistance erosion 

Advantages of Surface Irrigation

• Low initial cost
• Easy maintenance of the system
• Compatibility with all soil types
• Since it is widely used, most farmers have at least minimal understanding of how to operate and maintain the system.

Classification of Surface Irrigation

Surface irrigation is classified as under:

1. Wild flood irrigation 
2. Basin irrigation 
3. Border irrigation 
4. Furrow irrigation

Individually, each surface system has varied uses along with certain disadvantages depending upon factors such as initial cost, size and shape of fields, soil characteristics, nature and availability of the water supply, climate, cropping patterns, and influences external to the irrigation system.

1.Wild flood irrigation 

In wild flood irrigation, the water is administered to the field by ditch or pipe and flows over the soil surface through the crops. Though the process seems quite simple, wild flood irrigation tends to have a negative impact on the crop and soil, as both water and labor are often used inefficiently. This is because, with flooding, only half of the applied water is actually used by the crop, the other half is lost to evaporation, runoff, infiltration of uncultivated areas, and transpiration through leaves of weeds. Therefore, wild flood irrigation is mainly used on uneven terrains to irrigate pasture, hay, and small grains, which are not affected by sufficient water. In Spite of the shortcomings, it is to be noted that this technique is a great solution to irrigate lands that cannot be managed by other irrigation methods. 

2. Basin irrigation  

Basin irrigation is the oldest, most common and the simplest form of surface irrigation. This technique of irrigation requires a leveled soil surface and a narrow ridge about 15 – 50 cm high on all sides of the field which serves as a basin. The irrigated land is generally divided into smaller areas surrounded by small levees (an embankment built to prevent the overflow of a river). Water is transported into each basin by pipes and siphons, or through the levee. Excess water is drained from the land with surface drains on the low contour levee.  

Basin irrigation is suitable for crops such as maize, grains, cotton, or orchards where irrigation is used on moderate to slow intake soils and deep-rooted, closely spaced crops.

3. Border irrigation 

Another type of surface irrigation under surface is border irrigation. Border irrigation works on the principle of basin irrigation. Here, water is transported to the land through wide borders. The area between borders is called a border strip, on which the crops grow, which may range from 3-30 m (10-100 feet) in width. For efficient border irrigation, the border surface should be leveled across its width so the water can spread uniformly across it. Crops that are reactive to excessive water and soil that is too wet are not suitable to irrigate using this method.

4. Furrow irrigation 

Under furrow irrigation, water is transported from open ditches or pipes through small channels, or furrows, along with the land. The water flowing through the channel, penetrates the soil, thus irrigating crops. According to furrow direction and level, they can be classified into:

• Level furrow (lengthwise leveled furrows)
• Contour furrow (furrows curved to fit field topography)
• Graded furrow (straight channels down the field slope)

Furrow irrigation is suitable for crops that are reactive to very wet soil and excessive water over the stem. 

Though furrow irrigation does not require special farm equipment and can minimize irrigation costs, furrow irrigation does have certain disadvantages. Such as:

• Labor intensive technique 
• High probability of accumulation of salts in the furrows
• Furrow surface needs to be leveled
• It requires experience on the part of the farmer to divide water into each furrow and to maintain the correct flow. 

There are many other types of irrigation techniques that are quite popular. The following is a list of the most popular techniques of irrigation that is used:

II. Drip Irrigation

Drip irrigation is the most efficient water and nutrient delivery system for growing crops. It transports water and nutrients directly to the plant’s roots zone, in the right amounts, so that the plant gets exactly what is needed, to grow optimally. Drip irrigation enables farmers to produce higher yields while saving water as well as fertilizers. 

How Does it Work?

In drip irrigation, water and nutrients are transported across the land in pipes called ‘dripper lines’ also known as ‘drippers’. Each dripper emits drops containing water and fertilizers, resulting in the uniform application of water and nutrients directly to the plants, across the entire land.

Advantages of Drip Irrigation

• Soluble fertilizers and chemicals can be used
• Minimized fertilizer and nutrient loss due to localized application and reduced leaching
• Field levelling is not a priority thereby reducing labour
• Allows use of recycled non-potable water 
• Reduces soil erosion
• Helps tackle the problem of excessive weed growth 
• Uniform distribution of water as water is controlled by nozzle 
• Not a labour intensive technique thereby reduces labour cost
• Regulated supply of water on account of valves and drippers
• Plants remain dry thereby reduces the risk of diseases 
• Reduces energy cost as this technique uses lower pressure in comparison to other types of irrigation. 

Disadvantages of Drip Irrigation

• High initial cost
• The longevity of the tubes can be compromised due to exposure to sunlight 
• Proper filtration of water is of utmost importance to avoid blockage 
• Proper education of farmers is a must as avoid excess water as well as inadequate water supply 
• The users need to plan drip tape winding, disposal, recycle and reuse 
• If the system is installed improperly, it could lead to wastage of water time and effort but most importantly, it will lead to poor harvest
• Study of subjects like land topography, soil, water requirement as per crop type, etc. is a must for this system to provide optimal results
• In lighter soil subsurface, drip may be unable to wet the soil surface for germination. Therefore, careful consideration of the installation depth is of prime importance. 

III. Sprinkler Irrigation

In the sprinkler irrigation system, water is supplied by overhead high-pressure sprinklers or guns from one or more central locations within the field or from sprinklers on a moving platform. In other words, this system allows the application of water under high pressure with the help of a pump. It releases water similar to rainfall through small sprinklers placed in the pipes. Sprinkler irrigation is suited for most row, field and tree crops and water can be sprayed over or under the crop canopy.

Advantages of Sprinkler Irrigation

• Eliminates water conveyance channels, thereby reducing conveyance loss.
• Suitable in all types of soil except heavy clay.
• Saves water up to 30% – 50 %.
• Suitable for irrigation where the plant population per unit area is very high.
• Helps to increase yield.
• Suitable for undulating land.
• Saves land as no bunds required.
• Soluble fertilizers and chemical use are possible.
• Provides frost protection & helps in alteration of micro climate.
• Reduces labour cost.

Disadvantages of Sprinkler Irrigation

• High initial cost
• Requires constant energy 
• Poor application efficiency under high wind and temperature 
• Leaf burning due to high salinity of water in temperature higher than 95°F
• Uneconomical in cases where land is already levelled and developed
• Loss of water due to evaporation 

1.Center Pivot irrigation 

Center pivot irrigation, is a technique of irrigation where the crops are watered with sprinklers through an equipment that rotates around a pivot. This method is also called water wheel or circle irrigation. 

2. Lateral move irrigation 

In lateral move irrigation, the water is distributed through a series of pipes and sets of sprinklers. It is to be noted that Centre Pivot systems are anchored at one end and rotate around a fixed central point whereas Lateral systems are not anchored and both ends of the machine move at a constant speed up and down a paddock.

3. Sub-irrigation 

Sub-irrigation is an irrigation practice used in areas with relatively high water tables or where the water table can be artificially raised to allow the soil to be moistened from below the root zone through a system of pumping stations, canals, weirs, gates and ditches. 

Types of Irrigation- Traditional Irrigation System 

Having studied the scientific methods of irrigation, let us now have a look at the traditional methods used for irrigation in the country. Under these methods, water from wells, lakes, canals is drawn out by different methods in different regions to irrigate fields. Cattle and human labour is used in these methods. The traditional methods are not necessarily efficient but are cheaper than scientific methods. 

1. Ditch Irrigation 

A traditional method where ditches are dug out and seedlings are planted in rows.

2. Moat

This system is also known as the pulley system. As the name suggests, a pulley is used to draw water from a well thereby making it a labor-intensive method.

3. Chain pump

A chain pump consists of two large wheels connected by an endless chain. The bottom wheel is immersed halfway in the water resource. The buckets are attached to the chain and as the wheels turn, the buckets attached to it draws out water. The chain later lifts the buckets to the upper wheel where the water is deposited into a source. And the empty bucket gets carried back down.

4. Dhekli 

This system involves drawing water from a well or a similar water resource. Here, a rope and a bucket is tied to a pole and at the other end, a heavy stick is tied as a counterbalance. This rope is used to draw water. 

5. Rahat (Lever system)

Here, water is drawn from a well with the help of cattle- animals such as cows, buffaloes, etc. These animals are connected to a wheel and as the animals move, the wheel rotates thereby helping to draw water from the well.

Importance of Irrigation

The importance of irrigation can be explained in the following points:

1. Insufficient and uncertain rainfall adversely affects agriculture. Droughts and famines are caused due to low rainfall. Irrigation helps to increase productivity even in low rainfall.
2. The productivity on irrigated land is higher as compared to the un-irrigated land.
3. Multiple cropping is not possible in India because the rainy season is specific in most of the regions. However, the climate supports cultivation throughout the year. Irrigation facilities make it possible to grow more than one crop in most of the areas of the country.
4. Irrigation has helped to bring most of the fallow land under cultivation.
5. Irrigation has stabilized the output and yield levels.
6. Irrigation increases the availability of water supply, which in turn increases the income of the farmers.

THE CURRENT CHALLENGES:

• Natural Resources Degradation: Degradation of natural resources is emerging a global threat. The problem of land degradation in the rainfed or dry-land areas is expected to proceed at more than twice the rate.
• Decrease in per capita Arable Land Area: The prime agricultural land in the country is being converted to industrial, urban, recreational and other non-agricultural uses.
  • Solution: In view of the shrinking arable land resource, identifying and implementing strategies of restoration of degraded soils and intensification of existing prime agricultural land is important.
• Lack of irrigation: Agriculture is subject to the vagaries of monsoon in the country. As per World Bank, only 35% of India’s agricultural land is irrigated (artificial application of water to land or soil). The remaining 65% of farming is rain-dependent, most of which takes place over just a few summer months.
  • Solution: New technology and better farm management can be deployed to improve irrigation systems.
• Overexploitation of groundwater: Another major issue is overexploitation of groundwater, which is a major concern in states of Haryana, Delhi, Punjab, Tamil Nadu, Rajasthan, etc. Alarmingly, the groundwater level has been going down in almost all parts of the country.
• Currently, India is the largest user of groundwater in the world, extracting groundwater to the tune of 253 cm per year, about 25% of the global groundwater extraction.
  • Solution: Watershed management can be a useful technology for effectively recharging the groundwater by water and soil conservation methods.
• Droughts: Droughts connotes a situation of water shortage for human and agricultural consumption, which results in economic losses.
  • Solution: The situation calls for evolving an overall policy framework that can provide adequate incentive and opportunities for soil and moisture conservation.
• Desertification: Increasing desertification of India’s soil, is a fundamental threat to every activity of agriculture.
  • Solution: The government needs to formulate an appropriate strategy for desertification control and involve natural resource planning at the watershed level through a watershed management program. India is committed to combat desertification and land degradation and the country intends to achieve land degradation neutral status by the year 2030.
• Deforestation: The global annual rate of deforestation is estimated at 12.37 Mha or 0.82%/yr. India has 24 percent of land under forest as against the desired 33 % of National Forest Policy of 1988. A large part of these forests is degraded and productivity is very poor.
  • Solution: In the case of deforestation, watershed management can help in planning for judicious management of forest ecosystems, and in the restoration of degraded soils.

• Water Scarcity: Water crisis is usually viewed in terms of an increasing imbalance between water supply and demand.
• At present, India is suffering from “the worst water crisis in its history”, placing millions of lives and livelihoods under threat.
• According to the Aqueduct Water Risk Atlas released by the World Resources Institute (WRI), India is at 13^th position among the world’s 17 ‘extremely water-stressed’ countries.
• A region is said to be under ‘water stress’ when the demand for water exceeds the available volume or when poor quality restricts use.
• Solution: Watershed based management practices can effectively address the problem of water scarcity to a major extent.

GOVERNMENT MEASURES TO IMPROVE THE IRRIGATION SYSTEM: 

Pradhan Mantri Krishi Sinchayee Yojana:

• Launched in 2015 with the motto of “Har Khet Ko Paani”, the scheme aims to provide end-to-end solutions in the irrigation supply chain (water sources, distribution network and, farm-level applications).
• The scheme focuses on creating sources for assured irrigation and protective irrigation by harnessing rainwater at micro level through ‘Jal Sanchay’ and ‘Jal Sinchan’.
• One of the most crucial components of the initiative is “Per Drop More Crop”. It focuses on micro-irrigation systems (sprinkler, drip, pivots, rain-guns, etc.) to promote precision farming by making water available in a targeted manner to the root zone of crops.

Micro Irrigation Fund:

• The Government has created a dedicated Micro Irrigation Fund with NABARD.
• This fund aims to facilitate the States in order to mobilize the resources for expanding coverage of Micro Irrigation in the country.

Rainfed Area Development Programme (RADP):

• Rainfed Area Development Programme (RADP) is an initiative which aims to increase agricultural productivity of rainfed areas in a sustainable manner by adopting appropriate farming system-based approaches.

JAL SHAKTI MINISTRY: 

Recently, the government created the Jal Shakti Ministry s to provide access to safe drinking water by reorganizing the earlier ministries:

• Ministry of Water Resources, River Development, and Ganga Rejuvenation
• Ministry of Drinking Water and Sanitation
• The Ministry will focus on ensuring clean water for people and irrigation water facilities for farmers in the country.

Considering the rising water scarcity and depleting groundwater resources, there is a significant need for an appropriate irrigation system. Though the government has started various policies and programs to improve irrigation, more innovative policies are needed to be tailored to directly improve efficiency, boost productivity and minimize the environmental impact on farming. Everything said and done, the ultimate success of agriculture in any country of the world entirely depends on appropriate irrigation structure

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