Irrigation: Types, Systems & Water Management

1. Importance of Irrigation

India receives ~75% of its rainfall during the 4-month southwest monsoon — making irrigation essential for year-round cultivation. Only about 48% of India's net sown area is irrigated; the remaining 52% is rain-fed and highly vulnerable to droughts. Irrigation is critical for:

• Multiple cropping (growing 2-3 crops/year on same land)
• High Yielding Variety (HYV) seed utilization (cannot use HYVs without assured water)
• Reducing agricultural risk and farmer income volatility
• Extending agriculture to dry regions

2. Types/Sources of Irrigation

Canal Irrigation:

• Water drawn from rivers through a network of main canals, branch canals, distributaries, field channels.
• Two types: (a) Flow canals — river water flows by gravity (prevalent in Northern India — Indus, Ganga plains), (b) Lift canals — water pumped from rivers (prevalent in Deccan, lower-lying areas).
• Inundation canals — seasonal, fed by flood waters.
• Perennial canals — fed by dams/reservoirs for year-round supply.
• Major systems: Indira Gandhi Canal (Rajasthan), Upper Ganga Canal, Punjab canal system.
• Contributes ~33% of irrigated area.

Tank Irrigation:

• Small/medium ponds/reservoirs created by constructing earthen bunds to collect rainwater.
• Traditional system — prevalent in South India (Tamil Nadu, Andhra Pradesh, Telangana, Odisha, Karnataka).
• Low maintenance cost; recharge groundwater; many are community-managed.
• Challenge: Many tanks silted up, encroached, or poorly maintained — need rejuvenation.
• Contributes ~5% of irrigated area.

Well and Tubewell/Groundwater Irrigation:

• Extraction of groundwater through open wells (traditional) or tubewells with electric/diesel pumps.
• Largest single source of irrigation in India — ~60% of irrigated area.
• Concentrated in areas with favourable aquifer conditions: Indo-Gangetic Plain, Gujarat, Rajasthan.
• Challenge: Groundwater depletion is reaching critical levels in Punjab, Haryana, western UP, Rajasthan. India extracts ~25% of world's groundwater. CGWB (Central Ground Water Board) monitors aquifer health.

Drip Irrigation:

• Water delivered directly to plant root zone through a network of pipes, emitters, and drippers. Application efficiency ~90%+ vs. flood irrigation ~30-40%.
• Highly suitable for horticultural crops, sugarcane, cotton.
• PM Krishi Sinchayee Yojana (PMKSY) — Har Khet Ko Pani + Per Drop More Crop — promotes drip and sprinkler.
• Israel model: Drip irrigation pioneered; India applying it in dry Gujarat, Maharashtra, Karnataka.

Sprinkler Irrigation:

• Water sprayed over crops through a pressurized pipe system fitted with rotating heads.
• Suitable for wheat, vegetables, orchards.
• More efficient than flood, less than drip. Reduces evapotranspiration.

Others:

• Flood/Surface irrigation: Most common, least efficient (30-40% efficiency). Large volumes water applied to fields, most lost to evaporation/runoff.
• Lift Irrigation: Motor pumps draw water from rivers/canals and distribute — useful where gravity flow not possible.
• Rainwater Harvesting: Traditional structures (johads, baolis, kunds, percolation tanks) capture monsoon rainwater for dry season use. Rajasthan Tarun Bharat Sangh — community creek revival movement.

3. Irrigation Intensity

Irrigation Intensity = (Gross Irrigated Area / Net Irrigated Area) × 100. It shows how many crops are taken from same land — higher values indicate multiple cropping under irrigation. Punjab (~190%) has very high intensity; rain-fed states have low intensity.

4. Water Management Challenges

Groundwater Depletion: Annual groundwater extraction exceeds annual recharge in many districts — dark zones, semi-critical, critical. Punjab: only 2-3 more decades of current extraction sustainable. Policy: Pradhan Mantri Krishi Sinchayee Yojana (PMKSY) promotes water use efficiency. Water Pricing: Irrigation water in most states is provided free or at highly subsidized rates — no incentive for efficient use. Flat-rate pricing rather than volumetric pricing means farmers use excess water ("Jal shakti" reforms). Inter-State Water Disputes: Cauvery (Karnataka-Tamil Nadu), Krishna River (Andhra-Telangana-Karnataka), Satluj-Yamuna Link (Punjab-Haryana). Adjudicated by Interstate Water Disputes Act 1956 Tribunals. Salinity and Waterlogging: Over-irrigation, especially canal-fed, leads to waterlogging (raising water table) and soil salinity (salt deposits left by evaporation) — reduces agricultural productivity. Prevalent in western UP, parts of Punjab and Haryana. Climate Change: Changing monsoon patterns, reduced snowpack (depleting Himalayan glacier-fed rivers), increased drought frequency — all threaten water availability.

5. Government Schemes for Irrigation

PMKSY (Pradhan Mantri Krishi Sinchayee Yojana):

• Launched 2015: Har Khet Ko Pani (water to every field) + Per Drop More Crop (micro-irrigation efficiency).
• Amalgamated AIBP (Accelerated Irrigation Benefits Programme), IWMP (Watershed Development), ONWC (On-Farm Water Management).

AIBP (Accelerated Irrigation Benefits Programme):

• Completes long-stalled major/medium irrigation projects — 99 projects of 76 lakh hectare potential under PMKSY-AIBP.

Micro-Irrigation Fund: NABARD operates ₹5000 crore fund to facilitate drip/sprinkler adoption.

6. National Water Policy

National Water Policy 2012: Guiding framework for water sector. Key principles:

• Water as an economic good — volumetric pricing, regulated market.
• Right to a minimum quantity of water for life/livelihood.
• Demand management — efficiency improvement over supply augmentation.
• Integrated Water Resources Management (IWRM).
• Treating river basins as integrated planning units.
• Participation of local communities in water management.

Jal Shakti Ministry: Created in 2019 merging Water Resources and Drinking Water ministries. Jal Jeevan Mission: Har Ghar Jal — tap water connections to all rural households by 2024. Atal Bhujal Yojana: Community-managed groundwater management in over-exploited aquifer regions (7 states).

7. Environmental Effects of Irrigation

• Waterlogging and soil salinity (already ~2.5 million ha affected).
• Loss of biodiversity in wetland ecosystems.
• Altered river flow regimes affecting aquatic ecosystems.
• Canal seepage increases waterlogging along canal banks.
• Large dams: displacement of communities (SSP — Sardar Sarovar Project displaced thousands), submergence of forests and cultural heritage.