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Need of Irrigation in India
The rainfall in India is very erratic in its spatic as well as temporal variations. The average annual rainfall for India has been estimated at 1,143 mm which varies from 11,489 mm around cherrapunji in Assam (with the maximum one-day rainfall equal to 1040 mm) to 217 mm around Jaisalmer in Rajasthan. Besides, 75% to 90% of the annual rainfall occurs during 25 to 60 rainy days of the four monsoon months from June to September (2). In addition, there is also a large variation from year to year, the coefficient of variation being more than 20% for most parts of the 20% for most parts of the country (2).
Erratic behaviour of the south-west monsoon is the maintdroughtscause (Table 1.0) and floods. The recent proposal (Appendix-1) of the Government of India on interlinking of some major rivers of the country is aimed at (i) increasing the utilizable component
of the country’s water resources,problemsofshortages andexcesses(ii)ofwaterSol in some parts of the country. Table shows the values of the approximate probability of deficient rainfall (deficiency equal to or greater than 25 per cent of the normal) for different regions (8) Dependability of rainfall is thus rather low from the agriculture point of view and storage is essential to sustain crops during non-monsoon periods and also to provide water for irrigation during years of low rainfall. For a large part of any crop season, the evapotranspiration (i.e., the water ned of a crop) exceeds the available precipitation and irrigation is necessary to increase food
and fibre production. About 45 per cent of agricultural production in India is still dependent on natural precipitations. The need and important of irrigation in India can be appreciated from the mere fact that the country would need to produce meet the per capita requirement of 225 kg (i.e., about one-foruth of a tonne) per year for an estimated population of 1,231 million in the year 2030.
Table: Frequency of droughts in India (7)
Quarter Century 1801-25 1826-50 1851-75 1876-1900 1901-50 1926-50 1951-75 1976-2000
Drought Years 01,04,06,12,19,25 53,60,62,66,68,73 53,60,62,66,68,73, 77,91,99, 01,045,07,11,13,15,18,20,25, 39,41 51,65,66,68,72,74 79,82,85,87
Frequency of droughts 6 3 6 3 10 2 6 4
Table Periodicity of droughts in different regions (8)
Region : Recurrence of the period of deficient rainfall
Assam : Very rare, once in 15 years
West Bengal, Madhya Pradesh, Konkan, Coastal Andhra Pradesh, Maharastra, Kerala , Bihar, Orissa : Once in 5 years
South interior Karnataka, eastern Uttar Pradesh Vidarbha, Gujarat, eastern Rajasthan, western Uttar Pradesh, : Once in 4 years
Tamil Nadu, Kashmir, Rayalaseema, Telengana : Once in 4 years
Western Rajasthan : Once in 2 years
In addition, the export of agricultural products earns a major part of foreign exchange. Because of vastly different climate in different parts of the country, a variety of crops are produced in India. The country exports basmati rice, cotton, fruits (mango, apple, grapes, banana etc), vegetables (potato, tomato etc). Flowers (rose etc.) and processed food products in order to earn
precious foreign exchange. Still further, about seventy percent of the country’s on i facilities in the country.
Development of Irrigation in India
Among Asian countries, India has the largest arable land which is close to 40 per cent of
Asia’s arable land (6). Only USA hasbeenmorepractised ara throughout the world since the early days of civilization. In India too, water conservation for
Augmentation of crop yields. New high yielding varieties of crops have higher water requirement for giving higher yields. Sugarcane and rice have higher requirements of water.
Exacting water requirement. The high yielding varieties of crops have more exacting requirement of water.
Cash crops cultivation. Cash crops require higher and assured supply of water with frequent watering for maturity.
Assured water supply. For successful arming, availability of water in needed quantum and at right times is very essential.
Orchards and gardens. Fruit trees grown in orchards and garden high higher requirement of water.
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