Water Footprint of Crop Calculator
Free Water footprint crop Calculator for agriculture food systems. Enter variables to compute results with formulas and detailed steps.
Reviewed by Daniel Agrici, Founder & Lead Developer
Formula
Water Footprint (m3/kg) = Total Water Use (m3) / Crop Yield (kg)
The total water footprint sums green (rain), blue (irrigation), and grey (pollution dilution) water. Each is water depth (mm) x 10 x area (ha) for cubic meters, divided by total yield in kg.
Worked Examples
Example 1: Irrigated Wheat
Problem:10-hectare wheat at 4,000 kg/ha, green water 350 mm, blue water 200 mm, grey water 60 mm.
Solution:Total water = (350+200+60) x 10 x 10 = 61,000 m3\nTotal yield = 4,000 x 10 = 40,000 kg\nWF = 61,000/40,000 = 1.525 m3/kg = 1,525 L/kg\nGreen: 57.4% | Blue: 32.8% | Grey: 9.8%
Result:1,525 L/kg | Green: 57.4% | Blue: 32.8% | Grey: 9.8%
Example 2: Rainfed Maize
Problem:5-hectare rainfed maize at 6,000 kg/ha, green water 500 mm, blue water 0, grey water 40 mm.
Solution:Total water = (500+0+40) x 10 x 5 = 27,000 m3\nTotal yield = 6,000 x 5 = 30,000 kg\nWF = 27,000/30,000 = 0.9 m3/kg = 900 L/kg\nGreen: 92.6% | Blue: 0% | Grey: 7.4%
Result:900 L/kg | Green: 92.6% | Blue: 0% | Grey: 7.4%
Frequently Asked Questions
What is the water footprint of a crop?
The water footprint of a crop measures the total volume of freshwater used to produce a unit of crop yield, typically expressed in cubic meters per tonne or liters per kilogram. It encompasses three components: green water (rainwater consumed through evapotranspiration), blue water (irrigation from surface or groundwater), and grey water (freshwater needed to dilute pollutants to acceptable standards). Understanding the water footprint helps assess the true water cost of food production.
What is the difference between green, blue, and grey water?
Green water refers to rainwater stored in the soil as moisture and consumed by plants through evapotranspiration, generally the most sustainable source. Blue water is surface and groundwater used for irrigation, which depletes water bodies and can cause environmental stress. Grey water represents the volume of freshwater required to assimilate pollutants such as fertilizer runoff to meet water quality standards. For most rainfed crops, green water dominates at 70-90% of the total footprint.
Which crops have the highest water footprint?
Among common crops, tree nuts like almonds and cashews have some of the highest water footprints at 9,000-16,000 liters per kilogram. Cotton requires about 10,000 L/kg, making it one of the thirstiest industrial crops. Rice has a footprint of roughly 2,500 L/kg due to paddy flooding. Beef cattle feed collectively requires about 15,400 L per kg of beef produced. In contrast, potatoes and sugar beets are water-efficient at 250-500 L/kg.
How is crop water use efficiency calculated?
Crop water use efficiency (WUE) is calculated as the ratio of crop yield to total water consumed, expressed as kg of crop per cubic meter of water. The formula is WUE = Yield (kg) / Total Water Consumed (m3). Higher values indicate more efficient water use. Modern irrigated wheat achieves WUE of 1.0-1.5 kg/m3, while rice achieves 0.5-0.8 kg/m3 due to standing water requirements. Improving WUE through drip irrigation and mulching can reduce footprints by 20-40%.
References
Reviewed by Daniel Agrici, Founder & Lead Developer · Editorial policy