5
mm/day
600
mm
600,000
m³
800,000
m³
800
ML
6,667
m³/day
5
mm/day
600
mm
600,000
m³
800,000
m³
800
ML
6,667
m³/day
The Crop Water Use Calculator estimates the total water consumed by a crop over its growing season. Using the FAO method of combining reference evapotranspiration (ETo) with a crop coefficient (Kc), it calculates daily and seasonal evapotranspiration, then converts to total volume for the cropped area. This information is vital for water resource planning, irrigation system design, and regional water allocation.
This calculator provides seasonal totals, which are useful for comparing crop water demands, planning water storage requirements, and assessing the feasibility of irrigation projects. For daily irrigation scheduling, use the Irrigation Water Requirement calculator instead.
The calculator follows the FAO-56 approach:
This uses an average Kc over the growing season. For more accurate seasonal totals, you can sum separate calculations for each growth stage (initial, development, mid-season, late season) with their respective Kc values and durations.
Inputs
Results
Rice over 120 days at 5 mm/day ETo uses about 660 mm seasonally, or 660,000 m³ (660 ML) for 100 ha.
Inputs
Results
Winter wheat over 180 days at lower ETo (3 mm/day) uses 459 mm seasonally, or 229,500 m³ for 50 ha.
Season-average Kc values include: wheat 0.80-0.90, maize 0.85-1.00, rice 1.00-1.15, cotton 0.80-0.95, soybean 0.85-1.00, citrus 0.60-0.75, grape 0.60-0.80, and sugarcane 1.00-1.20. These are averages across all growth stages. For detailed stage-specific values, consult FAO-56 tables.
One millimeter of water applied uniformly over one hectare equals 10 cubic meters (10,000 liters). So 5 mm/day over 10 hectares equals 500 m³ per day. This conversion (mm x ha x 10 = m³) is fundamental to irrigation engineering and water resource planning.
No. This calculator gives the net crop water requirement (the water actually consumed by the crop through evapotranspiration). The gross irrigation requirement will be higher due to irrigation system inefficiencies. Typical efficiencies are 40-60% for surface irrigation, 70-85% for sprinkler, and 85-95% for drip irrigation. Divide the net requirement by efficiency to get the gross water needed.
Roboculator Team
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