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Irrigation and drainage
Evolution of irrigation development
The history of irrigation development in India can be traced back to prehistoric times. Ancient Indian scriptures referred to construction of wells, canals, tanks and dams and their efficient operation and maintenance. Irrigation to produce food grains is known to have been in existence for over 5 000 years (Framji, 1987). There is evidence of irrigation being practised since the establishment of settled agriculture during the Indus Valley Civilization (in 2500 Before the Common Era [BCE]). These irrigation technologies were in the form of small and minor works. Traces of irrigation structures dating back 3 700 years have been found in the state of Maharashtra. During the Mauryan era (2 600-2 200 years ago), it is reported that farmers had to pay taxes for irrigation water from neighbouring rivers.
The Grand Anicut (Canal) across the Cauvery river in Tamil Nadu was begun 1 800 years ago and its basic design is still used today. In 1800, some 800 000 ha were irrigated in India. Major irrigation canals were built following the major famines at the end of the nineteenth century and, in 1900, the Indian peninsula (including Bangladesh and Pakistan) had some 13 million ha under irrigation. In 1947, India had about 22 million ha under irrigation. High priority has been given to irrigation with nearly 10 percent of all planned outlays since 1950 being invested in irrigated agriculture. This has resulted in the development of, on average, 0.6-0.7 million ha new irrigated schemes every year.
The emphasis on irrigation development was initially on run-of-the-river schemes. Subsequently, the need was felt for storage projects for either single or multiple purposes. Irrigation schemes are grouped under three categories: major (>10 000 ha), medium (2 000-10 000 ha) and minor (<2 000 ha) schemes. Minor irrigation projects generally have both surface water and groundwater as sources, while major and medium projects exploit surface water resources. In 1993 around 65 percent were minor schemes. In new major irrigation works, social and environmental costs (resettlement of displaced people, loss of biodiversity in submerged areas, etc.) are more systematically considered than in the past.
While in 1993 the ultimate irrigation potential of India was an estimated 113.5 million ha, new estimates give a figure of 139.5 million ha, of which 58.1 million ha for major and medium irrigation schemes and 81.4 million ha for minor irrigation projects. Of the 81.4 million ha of minor irrigation potential, groundwater based potential is estimated to be 64.1 million ha and the surface water based potential is 17.3 million ha.
Total area equipped for irrigation was around 66.3 million ha in 2008 (Table 5). Irrigation is mainly concentrated in the north of the country along the Indus and Ganges rivers: Punjab, Rajasthan, Uttar Pradesh and Madhya Pradesh. A classification of irrigation by origin of water is in common use in India. It differentiates irrigation from canals (29 percent in 2001), most of which are government canals, tanks (4 percent), groundwater wells (63 percent), the majority being privately owned and managed, and other or undefined sources (4 percent) (Figure 3). In 1993 the area equipped for irrigation was about 50.1 million ha of which irrigation by canals accounted for 34 percent (97 percent are government canals), tanks 6.5 percent, groundwater 53 percent (generally privately owned and managed) and other or undefined sources (6.5 percent). This shows that the use of groundwater for irrigation has increased considerably.
Of the 19.75 million minor irrigation schemes, groundwater schemes account for 18.5 million and the rest are based on surface water resources. The surface flow schemes typically comprise tanks and storage developed by construction of check dams. Groundwater schemes are composed of dug wells, dug cum bore wells, borings, and both shallow and deep tubewells. There is considerable variation in the development of minor irrigation from state-to-state. The full potential of minor irrigation has been tapped in Uttar Pradesh, Punjab, Haryana, Rajasthan. In some of the Union Territories it is as low as 18 percent in Manipur and 20 percent in Madhya Pradesh. Minor irrigation schemes are generally in the private sector and very few (6 percent) are owned by public institutions.
Over the past few decades, the main driving force behind the expansion of groundwater irrigation and improvement in agricultural productivity, was support to investment to provide electrical infrastructure and credit. Private groundwater irrigation, with shallow wells that serve 3-5 ha each, is considered to be the most cost-effective solution. Of the 18.50 million groundwater wells 16.43 million wells are in use (7.85 million dug wells, 8.10 million shallow tubewells and the rest deep tubewells). Development of groundwater resources varies from state-to-state. Groundwater is still available for exploitation in the eastern parts of the country, and in Madhya Pradesh, Chhattisgarh, specific pockets of Andhra Pradesh, Karnataka, Maharastra and Jammu and Kashmir. In Punjab, Haryana, Rajasthan, Gujrat and Tamil Nadu, exploitation exceeds the recharge to groundwater.
In many states, especially in the north (Uttar Pradesh, Punjab and Haryana), the conjunctive use of surface water and groundwater has been practiced using canal systems and tubewells or dug wells to increase the yield and general efficiency of the water system. Water from the tubewells, which are installed alongside existing canals, is added into the canals for use in the canal command areas. This practice helps prevent waterlogging, but requires that farmers adopt good management techniques.
The irrigation component of the Bharat Nirman Programme of the Government of India, a business plan for rural infrastructure, started in 2005, envisages the development of an additional irrigation area of 10 million ha through various irrigation schemes. Currently, 166 major, 222 medium and 89 environmental resources management (ERM) projects are reported to be ongoing in various states. The Government of India provides support to State Governments through the Accelerated Irrigation Benefits Program (AIBP) and other schemes.
In recent years, the development of sprinkler and localized irrigation has been considerable, mainly the result of the pressing demand for water from other sectors, a fact that has encouraged governments and farmers to find water-saving techniques for agriculture. Sprinkler irrigation was not widely used in India before the 1980s; however between 1985 and 1996 more than 200 000 sprinkler sets were sold. In 2004 the area under sprinkler irrigation was an estimated 1.4 million ha, while in 1996 it was about 0.7 million ha.
Localized irrigation is also expanding rapidly in India. This can be partly explained by the subsidies offered by the Government to adopt drip systems. From about 1 000 ha in 1985, the area under drip irrigation increased to 70 860 ha in 1991, mainly in Maharashtra, Andhra Pradesh and Karnataka. In 2004 the area under localized irrigation was about 578 207 ha (Figure 4). Drip-irrigated crops are mainly used in orchards, mainly grapes, bananas, pomegranates and mangoes. Localized irrigation is also used for sugarcane and coconut. In 2004 surface irrigation covered approximately 61.9 million ha. The approximate capital cost of sprinkler systems (excluding pump cost) ranges from US$345-450/ha. The approximate cost of localized irrigation is US$1 780-6 240/ha.
Water-harvesting systems, comprising tanks and other water conservation works, are devised to capture, store and distribute water for irrigation, besides meeting the municipal needs of the population. According to the third minor irrigation census carried out in 2001 the number of tanks, storage and other water conservation works is 0.457 million.
Role of irrigation in agricultural production, the economy and society
Irrigation development has enabled diversification of cropping patterns with crops grown all year round. The expansion of irrigation has not only directly enabled yield increases, it has also facilitated high input, high-yielding agriculture involving the use of chemical fertilizers and high-yielding varieties of wheat rice and maize. The food grain production has increased from about 50 million tonnes in 1951 to 213 million tonnes in 2004. Although irrigated crop yields have increased considerably, they are still low compared to those of other countries. This is mainly because of poor water management in many surface irrigation schemes.
In 2004, the harvested irrigated crop area covered around 76.8 million ha, of which 31 percent wheat, 29 percent rice, 2 percent maize, 7 percent oil palm, 6 percent vegetables and fruits and 5 percent sugarcane (Table 5 and Figure 5). In 1993, the total harvested area was an estimated 66.1 million ha.
Status and evolution of drainage systems
In 1991, drainage works had been undertaken on about 5.8 million ha, which was 12 percent of the irrigated area. Investment in drainage has been widely neglected and, where such investment has been made, poor maintenance has caused many drainage systems to become silted up. On the eastern Ganges plain, investment in surface drainage would probably have a larger productive impact, and at a lower cost, than investment in surface irrigation. In 2010, only some irrigation systems, predominantly of south and western India, have well laid out drainage systems.