Irrigation and Water Management
Irrigation questions test water sources and methods, scheduling at critical stages, and simple calculations of irrigation volume, duty and delta.
Basics
- Sources: canals (Sharda, Upper Ganga), tubewells (the main source in most of UP), tanks and lift irrigation.
- Methods: surface - flooding, check basin, furrow, ring basin for orchards; sprinkler for undulating and sandy soils; drip is the most efficient (saves 40–50% water) and supports fertigation.
- Water quality: electrical conductivity, pH and residual sodium carbonate; saline water damages germination.
- Critical stages: wheat at crown root initiation (20–25 days after sowing), tillering, flowering and milk stage; rice at transplanting, tillering and panicle initiation; mustard at flowering and pod filling.
Worked example
One hectare needs a 6 cm irrigation. Volume = 10,000 m² × 0.06 m = 600 m³. A tube-well discharging 30 litres/second = 0.03 m³/second, so time = 600 ÷ 0.03 = 20,000 seconds, about 5.6 hours. Running the pump for only 4 hours gives 0.03 × 14,400 = 432 m³ = 4.3 cm, which is below the requirement.
Traps that cost marks
- Using 1 ha = 1,000 m²; it is 10,000 m².
- Confusing litres/second with m³/hour (1 m³ = 1,000 L; 1 hour = 3,600 s).
- Writing drip as the best method for paddy; drip suits orchards and wide-row crops.
- Treating flood irrigation as efficient.
- Forgetting drainage: over-irrigation causes waterlogging and salinity.