🛠️ Rainwater Harvesting and Water Management
Rainwater Harvesting and Water Management.
Rainwater harvesting strengthens rainfed farming by capturing seasonal rainfall and reallocating it to critical crop stages during dry spells.
Rainwater Harvesting (RWH)
Rainwater harvesting is the process of collecting, storing, and utilizing rainwater for productive use during water-scarce periods.
Methods of Rainwater Harvesting
1. Farm Ponds
- Excavated ponds (dugout type) for storing runoff water
- Size: 20m × 20m × 3m depth stores ~1200 m³ (1.2 million liters)
- Lining: Silpaulin/HDPE liner to prevent seepage
- Use: Supplemental irrigation for 1–2 critical irrigations (life-saving irrigation)
- One farm pond per 5 hectare dryland farm recommended
2. Percolation Tanks
- Structures built across streams to impound water and recharge groundwater
- Water seeps into ground, recharging wells in downstream areas
- Capacity: 0.1–1.0 million m³
- No direct use of impounded water — purpose is solely recharge
3. Check Dams
- Small dams across stream channels to retard runoff velocity and promote infiltration
- Masonry check dam: Permanent; 2–5 m height; includes spillway
- Gabion check dam: Wire mesh cages filled with stones; semi-permanent
- Loose boulder check dam: Temporary; for small gullies
4. Rooftop Rainwater Harvesting
- Collection of rain falling on building roofs
- Stored in tanks for domestic use or directed to recharge wells
- Potential: 100 m² roof area in 800 mm rainfall region → 80,000 liters/year
5. Jalkund / Water Harvesting Pits
- Small pits (3m × 3m × 1.5m) lined with plastic
- Used in hilly/tribal areas of northeast India
- Low-cost individual farmer-level intervention
Water Use Efficiency in Rainfed Agriculture
Concept
Water Use Efficiency (WUE) = Crop yield (kg) / Water consumed (mm or m³)
Typical WUE values:
| Crop | WUE (kg grain/mm water) |
|---|---|
| Wheat | 8–12 |
| Sorghum | 5–10 |
| Groundnut | 3–6 |
| Chickpea | 5–8 |
Strategies to Improve WUE
- Match crop to rainfall: Select crops whose water requirement matches available rainfall
- Supplemental irrigation: 1–2 irrigations at critical stages increase yields by 50–100%
- Deficit irrigation: Apply less water than full ET requirement but at critical stages
- Soil organic matter: Increases water-holding capacity (1% increase in OM → 15,000 L more water/ha)
- Mulching: Reduces non-productive evaporation
- Ridges and furrows: Concentrate runoff in furrows near plant roots
Drought Management and Contingency Planning
Contingency Crop Planning
| Monsoon Scenario | Strategy |
|---|---|
| Normal onset, normal progress | Regular crops and varieties |
| Delayed onset (2 weeks) | Short-duration varieties of same crop |
| Delayed onset (4+ weeks) | Shift to short-duration crops (greengram, sesame) |
| Long mid-season dry spell | Thinning, mulching, foliar KNO₃ spray, life-saving irrigation |
| Early withdrawal | Harvest for fodder if grain not viable; conserve soil moisture for Rabi crop |
Summary Cheat Sheet
| Component | Key Point |
|---|---|
| Rainwater harvesting | Collect runoff in structures for supplemental irrigation and recharge |
| Water use efficiency | Match crop demand to water availability and prioritize critical growth stages |
| Drought response | Activate contingency plans based on monsoon delay and dry-spell severity |
| Farm resilience | Combine storage, moisture conservation, and adaptive crop planning |
References
2 sources • [1] [2]
References
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