Irrigation Water Requirement (IWR) is the amount of water
that must be supplied through irrigation to meet crop water demand
after accounting for effective rainfall.
Formula Used
IWR (mm) = ETc − Effective Rainfall
Water Volume (m³) = IWR (mm) × Area (ha) × 10
Where:
• ETc = Crop evapotranspiration (mm)
• Effective rainfall = Useful rainfall (mm)
• 1 mm water over 1 ha = 10 m³
Enter Field Data
Field Notes:
• ETc = ET0 × Kc
• Effective rainfall excludes runoff & deep percolation
• Used in canal scheduling & micro-irrigation design
