A Major part of India is located in the tropical and subtropical region. Being a hot country, with seasonal and irregular rainfall, irrigation is needed to carry on agricultural activities during the dry period.
Water has been in use for irrigation since ancient times. The Grand Anicut of the Kaveri River was built in the second century AD. In order to increase agricultural production, India has to improve the irrigation system. The increasing need for developing irrigation facilities in India is due to the following reasons:
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1. Uneven distribution of rainfall:
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The average annual rainfall in India is about 100 cm, which is not uniform throughout the country. In some parts, like Western Ghats and eastern India, the annual rainfall is more than 200 cm, while the leeward side of Western Ghats, and arid parts of Rajasthan receive much less rainfall. The lower amounts of rainfall with higher variability make irrigation essential to carry on agricultural operations.
2. Uncertainty of Rainfall:
The total amount of rainfall in India varies not only from place to place, but also from time to time. In many parts of India, the rainfall is highly variable, which leads to greater incidence of famines and droughts. Increased irrigation facilities can reduce the problem of droughts and thus protect agricultural crops.
3. Irregularity of Rainfall:
The main source of rainfall in our country is the southwest monsoon winds in the summer season. These winds are highly irregular and often cause a long dry spell during the rainy season. This creates water scarcity and failure of crops. This problem can be solved through effective and dependable sources of irrigation.
4. Seasonality of Rainfall:
The main rainy season in India is between June and October. The duration decreases from about 6 months in Assam to about 2 months in northwest India. About 90 per cent of the total annual rainfall is received during second half of the summer season. Thus, irrigation is needed to supplement the rain water to raise crops in the dry season.
5. Multiplicity of Crops:
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India has three cropping seasons Kharif, Rabi and Zaid. The Kharif crops are fully dependent on monsoon rains. The Rabi crops are raised on the soil moisture left after the harvest of Kharif crops or grown in areas with assured irrigation facilities. Zaid or summer crops are exclusively irrigated crops. The pressure of growing population forces the farmers to raise all the three crops.
6. Speciality of Crops:
Different crops require different quantities of water for growth. Millets barley, pulses, etc., need less water, while rice, sugar cane, wheat, potatoes, etc., need more water. The high yielding varieties using heavy doses of chemical fertilizers require more moisture, which can be given only through irrigation.
7. Commercialised Crops:
Many of the commercial crops need assured irrigation to improve the quality and quantity of their production. These crops generally need frequent watering which can only be managed through an efficient and reliable system of irrigation.
8. Nature of the Soil:
The need of irrigation is linked with the nature of the soil. The sandy loams need frequent watering due to less retentive capacity of moisture. On the other hand, the clayey soils have higher moisture holding capacity, and thus need less irrigation.