- Irrigation is the process of supplying water to crops using artificial means such as canals, tube wells, and tanks. It plays a crucial role in supporting agricultural growth, maintaining landscapes, and rehabilitating disturbed soils in dry regions and during periods of insufficient rainfall. In contrast, agriculture that solely relies on natural rainfall is known as rain-fed or dryland farming.
- India, with its large population, faces the challenge of meeting the demand for over 450 million tonnes of grain. However, climate change is leading to erratic weather patterns, making crops more susceptible to unpredictable rainfall.
- Currently, the productivity of irrigated land in India stands at around 2.5 tonnes per hectare, while rain-fed lands yield less than 0.5 tonnes per hectare. This highlights the urgent need for effective irrigation strategies and their implementation.
- India possesses approximately 4% of the world’s total annual river runoff. The per capita availability of natural runoff water is at least 1100 cubic meters per year.
Benefits of Irrigation
- Increased crop yield: Proper irrigation, delivering the right amount of water at the right time, enhances the production of various crops by meeting their specific growth requirements.
- Protection against famine: Regions with irrigation facilities are safeguarded against crop failures and famine caused by drought. In contrast, rain-fed areas depend solely on unpredictable rainfall, posing risks to farmers.
- Expansion of cultivated areas: Irrigation enables the cultivation of new lands, thereby increasing the overall area under irrigated cultivation.
- Cultivation of superior crops: With reliable water supply from irrigation, farmers can consider cultivating superior crop varieties or high-yielding crops. Rain-fed areas often lack the necessary water availability, making such cultivation impractical.
- Elimination of mixed cropping: In rain-fed regions, farmers often practice mixed cropping, planting multiple crop types in a single field to mitigate water scarcity risks. However, this reduces overall productivity. With irrigation, farmers can focus on cultivating a single crop variety, leading to increased yields.
- Economic development: Assured irrigation leads to consistent crop production throughout the year, benefiting farmers financially. The government also benefits through tax revenue generated from farmers utilizing irrigation facilities.
- Hydroelectric power generation: Canal-based irrigation systems often involve variations in elevation along the canal bed. These differences can be harnessed to generate electricity through small-scale hydroelectric projects, such as bulb-turbines installed in canals like the Ganga, Sarada, and Yamuna.
- Domestic and industrial water supply: Some water from irrigation canals can be utilized for domestic and industrial purposes in nearby areas. Compared to the water demand for irrigation, the requirements for domestic and industrial use are relatively small and have minimal impact on the overall canal flow. For instance, the town of Siliguri in West Bengal receives water supply from the Teesta Mahananda link canal.
Classification of Irrigation Schemes
- Irrigation systems can vary based on topology, water availability, land availability, and technological feasibility. Different schemes are used to classify irrigation systems, as discussed below:
Based on Source
- Irrigation sources depend on factors such as surface and underground water availability, land slope, soil nature, and types of crops grown in a region. The main sources of irrigation used in different parts of the country include:
- Wells and Tube-Wells:
- This traditional form of irrigation accounts for 62% of the total irrigated area in the country. Wells and tube-wells are relatively easy to install and provide irrigation in a short duration.
- Uttar Pradesh has the largest area under tube-well irrigation, followed by Rajasthan, Punjab, Madhya Pradesh, Gujarat, and Bihar.
- Canals:
- Canals used to be the primary source of irrigation, covering almost 50% of the total irrigated area in 1950-51.
- However, with the government’s promotion of tube-well irrigation in the 1960s, the percentage of canal-irrigated area decreased to less than 40% and currently stands at 26% in 2009-10.
- Canals are effective in low and leveled relief areas with a perennial source of surface drainage. Northern plains, Kashmir and Manipur valleys, and the Eastern Coastal plains are suitable regions for canal irrigation.
- Uttar Pradesh, Punjab, Haryana, and Western Rajasthan have high-density canal systems. In the Peninsular region, rivers like Damodar, Mahanadi, Godavari, Krishna, and Narmada have important canal systems. Uttar Pradesh ranks first in canal irrigation, followed by Andhra Pradesh.
- Tanks:
- Tanks, also known as irrigation reservoirs, are artificial or natural water storage structures. They are particularly important in peninsular India, where they serve as a significant source of irrigation.
- Approximately 3% of the total irrigated area is under tank irrigation. The states with the highest number of tanks are:
All tanks in the country:
- West Bengal: 21.2%
- Andhra Pradesh: 13.6%
- Maharashtra: 12.5%
- Chhattisgarh: 7.7%
- Madhya Pradesh: 7.2%
- Tamil Nadu: 7.0%
- Karnataka: 5.0%
- During the summer season, when additional irrigation is needed, many tanks dry up, leading to significant challenges. Approximately 15% of these tanks remain unused, resulting in the loss of around 1 million hectares of irrigation potential. Furthermore, even among the tanks that are in use, approximately 2 million hectares of potential are lost due to underutilization.
- The loss of potential due to non-use is particularly severe in Meghalaya, Rajasthan, and Arunachal Pradesh, where it exceeds 30%. On the other hand, the loss of potential due to underutilization is more than 50% in Gujarat, Nagaland, Rajasthan, the Andaman and Nicobar Islands, and Dadar and Nagar Haveli.
Based on Magnitude
- Irrigation projects in India are classified into three categories based on the Culturable Command Area (CCA):
- Major Projects:
- Projects with a CCA exceeding 10,000 hectares are categorized as major projects. These projects cover a significant area and play a crucial role in irrigation. They require substantial investment and infrastructure. Major projects contribute to the majority of the country’s irrigation potential.
- Medium Projects:
- Irrigation projects with a CCA between 2,000 and 10,000 hectares are classified as medium projects. While smaller in scale compared to major projects, they still have a substantial impact on irrigation. Medium projects cater to specific regions and contribute to the overall irrigation potential.
- Minor Projects:
- Irrigation projects with a CCA of 2,000 hectares or less fall under the category of minor projects. These projects primarily rely on both surface and groundwater sources.
- Minor projects are often implemented through individual or cooperative efforts of farmers, utilizing institutional finance and personal savings. They make a significant contribution to irrigation, especially in areas where major or medium projects may not be feasible.
- The ultimate irrigation potential of major and medium projects in India is estimated to be around 64 million hectares. Currently, approximately 66% of this potential has been achieved.
- The creation of irrigation potential through major and medium projects has increased over the years, with an average rate of 0.51 million hectares per year from 1951 to 1997. From 1997 to 2005, the creation rate increased to 0.92 million hectares per year, possibly due to the acceleration of projects through programs like the Accelerated Irrigation Benefit Programme (AIBP).
- The total potential created by minor irrigation projects by the end of the ninth plan was 60.41 million hectares, contributing to approximately 65% of the total utilized irrigation potential in the country.
- While major and medium projects may be suitable for certain areas, remote regions or those with divided land holdings may require the implementation of minor irrigation schemes. The aim is to reduce the overall cost of irrigation development while ensuring efficient utilization of available water resources.
Based on Distribution of Water
In addition to the classification based on magnitude, irrigation techniques can be categorized based on the distribution of water within the field. The two main techniques are:
Surface Irrigation
In surface irrigation systems, water flows over the land through gravity, wetting and infiltrating the soil. It is also referred to as flood irrigation, particularly when the land is flooded or nearly flooded. Surface irrigation can be further divided into:
- Basin Irrigation: Water is applied rapidly to the entire basin and allowed to infiltrate. Basins may be interconnected for sequential drainage.
- Furrow Irrigation: Small parallel channels are created along the field’s length, and water is applied at the top end of each furrow, flowing down the field under gravity.
- Localized Irrigation: This system distributes water under low pressure through a piped network in a predetermined pattern. It provides a small discharge of water to each plant or in its vicinity.
Drip Irrigation
Water is delivered drop by drop directly at or near the plant’s root zone. This method is highly efficient in water usage, reducing evaporation and runoff. It is often combined with plastic mulch and can also be used for fertigation (delivering fertilizer through the irrigation system).
- Spray or Micro-sprinkler Irrigation: Water is sprayed over the field using sprinklers or micro-sprinklers, covering a specific area.
- Bubbler Irrigation: Water is discharged through a device that creates bubbles, delivering it near the plants.
Sprinkler Irrigation
- Sprinkler or overhead irrigation involves the use of a piped water supply system with one or more central locations within the field.
- Water is distributed using high-pressure sprinklers or guns mounted overhead. This type of irrigation system is often referred to as a solid-set irrigation system.
- Rotating sprinklers driven by ball drives, gear drives, or impact mechanisms are called rotors. Guns are not only used for irrigation but also for industrial applications like dust suppression and logging.
- Sprinklers can be mounted on moving platforms connected to the water source via hoses. Traveling sprinklers are automatically moving wheeled systems that can irrigate areas such as small farms, sports fields, parks, pastures, and cemeteries without constant supervision.
- The field water efficiency of sprinkler irrigation ranges from 60% to 70%.
Sub-Irrigation
- Sub-irrigation, also known as seepage irrigation, has been used for field crops in areas with high water tables.
- It involves artificially raising the water table to moisten the soil from below the root zone of plants.
- These systems are commonly found in permanent grasslands in lowlands or river valleys and are combined with drainage infrastructure.
- Pumping stations, canals, weirs, and gates are used to control the water level in a network of ditches and manage the water table.
- Sub-irrigation is also utilized in commercial greenhouse production, particularly for potted plants. Water is delivered from below, absorbed upward by the plants, and the excess is collected for recycling. The three basic types of sub-irrigation are ebb-and-flow, trough, and flooded floor.
Adopting localized forms of irrigation, such as sprinkler and sub-irrigation, can present various challenges, including:
- Expense: The initial cost of installing these systems can be higher compared to overhead irrigation methods.
- Susceptibility to damage: Tubes used in drip irrigation systems may be affected by sunlight, reducing their usable lifespan.
- Clogging: Inadequate filtration and maintenance can lead to clogging issues in the irrigation equipment.
- Inefficient installation: Improper installation can result in water wastage, loss of time, and reduced harvest. These systems require careful consideration of factors such as land topography, soil type, water availability, crop type, agro-climatic conditions, and the suitability of the irrigation system components
Classification based on the Way Water is Applied
- Irrigation systems can also be classified based on the method of water application to agricultural land:
- Flow Irrigation System
- In this system, water is conveyed to the irrigated land by gravity. It can be further classified into the following categories:
- Direct Irrigation: Water is directly obtained from a river without any intermediate storage. A weir or barrage is constructed across the river to raise the water level, allowing a portion of the river flow to be diverted through an adjacent canal. The flow of water takes place naturally by gravity.
- Reservoir/Tank/Storage Irrigation: Water is obtained from a river and stored by constructing an obstruction such as a dam. This ensures a sufficient water supply even during periods of no inflow from the catchment. The stored water is then used to irrigate fields through a system of canals.
2. Lift Irrigation System
- In this system, the irrigation water source is located at a lower level than the land to be irrigated.
- Water is lifted using pumps or other mechanical devices and conveyed to the agricultural land through channels that flow by gravity. An example of a lift irrigation system is the Indira Gandhi canal in Rajasthan, which relies on lifting water to feed a significant portion of the cana
Classification based on the Duration of Applied Water:
- Irrigation systems can also be classified based on the duration of applied water. This classification considers the timing and availability of water for irrigation. The two categories are as follows:
- Inundation/Flooding Type Irrigation System
- In this system, large quantities of water from a river, typically during floods, are allowed to flow and inundate the cultivated land.
- This process saturates the soil with water. Subsequently, the excess water is drained off, and the land is utilized for cultivation.
- This type of irrigation relies on the floodwaters of rivers, which limits its availability to a specific time of the year.
- It is commonly practiced in areas near river deltas where the slope of the land and the river is gentle.
- However, due to river embankment practices implemented over the past century, the utilization of this irrigation method has declined.
- Perennial Irrigation System
- In this system, irrigation water is provided at regular intervals throughout the crop’s life cycle based on its water requirements. The water for this type of irrigation can be obtained from rivers or reservoirs.
- Therefore, the source of water can be either surface water or groundwater. The application of water in perennial irrigation systems can be done using flow irrigation or lift irrigation methods.
Irrigation efficiency
- Irrigation efficiency in India varies across different regions and crops. Here are some data and facts related to irrigation efficiency in India:
- Overall Irrigation Efficiency: The overall irrigation efficiency in India is estimated to be around 35-40%. This means that a significant amount of water applied for irrigation does not reach the plants’ root zones and is lost through evaporation, runoff, or inefficient distribution.
- Canal Irrigation Efficiency: Canal irrigation, which is a major source of irrigation in India, has an average efficiency of about 35-40%. This includes losses during conveyance, distribution, and field application.
- Groundwater Irrigation Efficiency: Groundwater irrigation, predominantly through tube wells, has relatively higher efficiency compared to canal irrigation, ranging from 45% to 60%. However, it still involves some losses due to inadequate infrastructure, improper maintenance, and over-extraction of groundwater leading to water table depletion.
- Drip Irrigation Efficiency: Drip irrigation is a highly efficient method of irrigation that can significantly reduce water loss. Drip irrigation systems in India have demonstrated efficiency levels of 70% to 90%. This technology delivers water directly to the plant roots, minimizing evaporation and runoff.
FAQs
Q1. What are some examples of ancient irrigation systems in India?
- Qanat System: This underground tunnel system was used to extract groundwater for irrigation and domestic use.
- Stepwell Systems: These elaborate wells with steps leading to the water level were used to store and regulate water supply for irrigation.
Q2. How did ancient irrigation systems in India impact agriculture?
- These systems significantly enhanced agricultural productivity, allowing for the cultivation of crops in regions with scarce rainfall.
- They facilitated the growth of civilizations by providing a reliable water supply for farming, leading to the development of prosperous agricultural communities.
Q3. What are the names of two prominent irrigation systems in India?
- Indira Gandhi Canal: Located in the northwestern part of India, it serves the state of Rajasthan, providing water for irrigation and drinking purposes.
- Godavari River Basin Irrigation Projects: These projects include various irrigation systems like the Sriram Sagar Project and the Polavaram Project, aiding agricultural activities in the Godavari river basin.
Q4. What are the different types of irrigation systems commonly used in India?
- Surface Irrigation: This system involves the application of water directly to the soil surface, allowing it to infiltrate and be absorbed by the roots.
- Sprinkler Irrigation: Water is distributed by high-pressure sprinklers, simulating natural rainfall and ensuring uniform water distribution over the fields.
- Drip Irrigation: This system delivers water directly to the base of the plant, minimizing evaporation and maximizing water usage efficiency.
- Subsurface Irrigation: It involves the application of water directly to the root zone through buried perforated pipes or tubes, reducing water loss through evaporation and surface runoff.
Q5. What is the ancient irrigation system in the northeast part of India?
Ans. Bamboo Drip Irrigation System: This ancient system, found in the hilly regions of northeast India, used bamboo pipes to transport water from natural springs to agricultural fields for irrigation.
Q6. What is the approximate price range of automatic drip irrigation systems in India?
Ans. The cost of automatic drip irrigation systems in India can vary depending on factors such as brand, quality, coverage area, and additional features. On average, these systems can range from INR 5,000 to INR 50,000, with more sophisticated systems potentially exceeding this range.
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