Irrigation Water Distribution
Definition
Irrigation water distribution refers to the conveyance and allocation of water from the source (canal, well, tank, reservoir) to the farm fields in a timely, equitable, and efficient manner for crop production.
Levels of Water Distribution
- Main system → Reservoir / Main canal → distributaries.
- Secondary system → Minors → watercourses.
- On-farm system → Field channels, ditches, furrows, border strips, basins.
- Methods of Irrigation Water Distribution
(a) Canal Command Distribution
- Warabandi System (Punjab, Haryana, Rajasthan):
- Rotational water allocation to farmers.
- Each farmer gets a fixed turn (time slot) proportional to landholding.
- Ensures equity between head- and tail-end farmers.
(b) On-Farm Distribution
- Field channels: Permanent earthen, brick, or lined channels → minimize seepage loss.
- Piped distribution: Underground PVC/HDPE pipes → saves 20–25% water.
- Modern pressurized systems: Drip, sprinkler → direct delivery to root zone.
- Cut-back irrigation: High initial flow, later reduced → improves uniformity.
- Surge irrigation: Water applied intermittently in furrows → improves infiltration uniformity.
- Principles of Efficient Distribution
- Equity → Fair share among farmers.
- Timeliness → Supply when crops need it most.
- Adequacy → Quantity should meet crop requirement.
- Flexibility → Adjusting to crop type, soil, season.
- Efficiency → Minimize conveyance and distribution losses.
- Challenges in Water Distribution
- Head-tail inequity in canal commands.
- Seepage & evaporation losses: up to 30–40% in unlined canals.
- Poor maintenance of field channels.
- Over-irrigation at head end → waterlogging & salinity.
- Conflicts among farmers due to shortage or mismanagement.
- Solutions / Management Approaches
- Canal lining → reduces seepage loss by 10–15%.
- Laser land leveling → uniform distribution, saves 20–25% water.
- Participatory Irrigation Management (PIM) → Water User Associations (WUAs) for equitable sharing.
- Rotation & scheduling → Based on crop water requirement (e.g., IW/CPE ratio).
- Micro-irrigation → Direct delivery, high efficiency (80–90%).
- ICT-based monitoring → Remote sensing, soil moisture sensors, mobile apps for irrigation scheduling.
- Some Facts for Exam
- Conveyance loss in unlined canals: 30–40%.
- Irrigation efficiency in India: Surface 30–40%, Sprinkler 60–70%, Drip 80–90%.
- Warabandi introduced in Punjab → now followed in Haryana, Rajasthan.
- Waterlogging affects ~8.4 million ha in canal commands.
- Lining field channels improves conveyance efficiency from 60% → 80–85%.
