Irrigation Water Requirement
Estimate daily and seasonal crop water demand using the FAO reference ET method.
BAgSci, DipAg, Certified Farm Advisor (NZIPIM)
Agricultural scientist and farm advisor with 18 years across sheep/beef, dairy, and arable operations in New Zealand and Australia.
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About the Irrigation Water Requirement
Crop water requirement (ETc) = Reference ET₀ × Crop coefficient (Kc). ET₀ varies daily with temperature, humidity, wind and solar radiation.
Gross irrigation = Net requirement ÷ Application efficiency. Flood irrigation is ~65% efficient; pivot sprinklers ~80–90%; drip irrigation ~90–95%.
How it works
ET_c = K_c \times ET_0