Irrigation systems
Macro and micro irrigation and traditional water harvesting such as johads, khadins and eris.
Why irrigation matters
Indian rainfall is seasonal and uneven, so irrigation decides how much and how often land can be cropped. Irrigation can be grouped by scale and technique.
Macro (large-scale) irrigation
In India, projects are classed by their culturable command area (CCA): major projects above 10,000 hectares, medium projects between 2,000 and 10,000 hectares, and minor projects below 2,000 hectares. Major projects use big dams and canal networks (for example, the Bhakra–Nangal system). They give assured water but can cause waterlogging and salinisation when too much water is applied and drainage is poor, along with displacement of people and loss of forests.
Micro irrigation
- Drip irrigation delivers water drop by drop through pipes and emitters to the root zone. Field efficiency can be around 90%, compared with roughly 30–50% for flood irrigation. It suits orchards, vegetables and dry regions, and fertiliser can be mixed in (fertigation).
- Sprinkler irrigation sprays water like rain; it suits uneven land and sandy soils.
Both save water and reduce weed growth and salinity, but need investment.
Traditional water harvesting
- Johad: a small crescent-shaped earthen check dam that stores runoff and recharges groundwater (Rajasthan, Haryana). The NGO Tarun Bharat Sangh, led by Rajendra Singh, revived johads in Alwar district and helped the Arvari river to flow again.
- Khadin: an embankment built across the lower slope of a farm in western Rajasthan (Jaisalmer); runoff collects behind it and crops are grown on the moist bed. It is associated with the Paliwal Brahmins.
- Eri: a tank system of Tamil Nadu, often in chains, managed by the village, which also controls floods and recharges groundwater.
- Others: kuhls (Himachal Pradesh), zabo (Nagaland), bamboo drip (Meghalaya), ahar–pyne (south Bihar) and kunds (Rajasthan).
Key points
- Major > 10,000 ha, medium 2,000–10,000 ha, minor < 2,000 ha CCA.
- Over-irrigation without drainage causes waterlogging and salinity.
- Drip is the most water-efficient common method.
- Johad, khadin and eri are community-managed harvesting systems.
Exam tips
- Pair each structure with its state: johad–Rajasthan, khadin–Jaisalmer, eri–Tamil Nadu, kuhl–Himachal, zabo–Nagaland.
- Questions often ask which method suits a dry, sandy or uneven area; think drip or sprinkler.