Water Use Efficiency (WUE)
Enter yield (kg/ha) and seasonal water depth (mm) to compute water volume per hectare and water use efficiency WUE = yield ÷ volume (kg/m³), assessing irrigation output efficiency.
Input Data
Results
At a glance:Crop water use efficiency (WUE) measures how much dry matter or economic yield a crop produces per unit of water consumed — the core indicator of irrigation and cultivation water efficiency. Compute in two steps: first convert the seasonal water depth (mm) to a per-area water volume — since 1 mm depth over 1 hectare (10000 m²) equals 10 m³, water volume(m³/ha) = water depth(mm) × 10; then WUE = yield(kg/ha) ÷ water volume(m³/ha) gives kilograms per cubic metre (kg/m³). Higher WUE means more yield per water, more efficient use. It is affected by crop species, cultivar, climate, soil and irrigation management: C4 crops (maize, sorghum) usually have higher WUE than C3; deficit irrigation, mulching, better roots and drought-tolerant breeding all raise WUE. In water-scarce regions, raising WUE means 'more grain with less water', a key goal of sustainable agriculture.
Formula
Water volume: volume(m³/ha) = water depth(mm) × 10 (1 mm/ha = 10 m³).
Water use efficiency: WUE(kg/m³) = yield(kg/ha) ÷ volume(m³/ha).
Equivalent: WUE = yield(kg/ha) ÷ (10 × water depth mm).
$$V_{water} = 10 \times W_{(mm)}$$$$WUE = \frac{Y_{(kg/ha)}}{V_{water}} = \frac{Y_{(kg/ha)}}{10 \times W_{(mm)}}$$How to Use
- Enter yield per area Y (kg/ha), grain or dry matter.
- Enter seasonal water depth W (mm, irrigation plus effective rainfall).
- The tool returns water volume per hectare and WUE (kg/m³); higher means more efficient use.
Approximate WUE ranges for common crops
| Crop / type | WUE (kg/m³) | Note |
|---|---|---|
| Maize (C4) | 1.5–2.5 | High photosynthetic efficiency, good yield per water |
| Wheat (C3) | 0.8–1.6 | Temperate staple, wide management range |
| Rice | 0.6–1.2 | High water demand, lower WUE |
| Vegetables (leafy) | 5–15 | Fresh weight, high water content, larger number |
Ranges are approximate, varying with cultivar, climate, soil and irrigation. Fresh-weight vegetables show much larger WUE than grains measured by dry weight/grain.
Case Studies
WUE of a maize field
A maize field yields 8000 kg/ha; seasonal water depth 500 mm (irrigation + effective rainfall).
Water volume = 500 × 10 = 5000 m³/ha; WUE = 8000 ÷ 5000 = 1.6 kg/m³.
1.6 kg/m³ is a reasonable maize level, about 1.6 kg grain per cubic metre of water.
Water-saving irrigation raises WUE
Same field with deficit irrigation, water depth drops to 400 mm, yield holds ~7800 kg/ha.
Water volume = 400 × 10 = 4000 m³/ha; WUE = 7800 ÷ 4000 = 1.95 kg/m³.
Yield drops only 2.5% but WUE rises ~22%, showing the value of moderate water saving in dry conditions.
FAQ
Should I enter irrigation or total water use as W?
Depends on what you assess. For 'irrigation water' efficiency, enter irrigation depth; for overall crop water efficiency, enter total seasonal water use — irrigation plus effective rainfall (or accumulated crop ETc). The WUE denominator differs in literature, so confirm the same definition when comparing, otherwise the numbers are not comparable.
Why is 1 mm water depth equal to 10 m³/ha?
1 hectare = 10000 m², and 1 mm depth = 0.001 m, so volume = 0.001 m × 10000 m² = 10 m³. Thus water depth(mm) × 10 is the per-hectare volume (m³). This conversion maps a depth in mm directly to volume, convenient to divide by yield (kg/ha) into kg/m³.
Use fresh or dry weight for yield?
Either, but state it. Grains use air-dry grain or standard-moisture yield; forage and vegetables use fresh or dry matter. High-moisture fresh weight inflates WUE (leafy greens can reach 5–15 kg/m³), while dry-matter WUE is smaller. For cross-crop or cross-study comparison, unify to one basis (usually dry matter or standard moisture).
How to raise crop water use efficiency?
Three routes: reduce invalid loss — plastic or straw mulch to suppress soil evaporation and avoid deep percolation; improve irrigation method and scheduling — drip and deficit irrigation at key stages; and breed drought-tolerant, efficient cultivars with rational fertilization for roots and photosynthesis. These lower water use without clear yield loss, raising WUE.
Is WUE the same as irrigation water productivity?
Close but not identical. WUE generally is yield over crop water consumption (evapotranspiration); 'irrigation water productivity' uses water delivered to the field as denominator and is further affected by irrigation efficiency. This calculator uses water depth as denominator, closer to irrigation water productivity; if you interpret the depth as accumulated ETc, it is closer to typical WUE. Just state the denominator definition when using it.
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References
Content review: Calculatorism Science Team. Results are for reference only; please refer to the relevant authorities for the official figures.