Example Data Table
| Crop | Area (m²) | Yield (kg) | Irrigation (L) | Rainfall (mm) | Efficiency (%) | Losses (%) |
|---|---|---|---|---|---|---|
| Tomato | 20 | 12 | 250 | 15 | 85 | 10 |
| Lettuce | 12 | 8 | 140 | 10 | 90 | 8 |
| Cucumber | 18 | 15 | 320 | 5 | 80 | 12 |
Use this table to test the calculator and compare seasonal changes.
Formula Used
This calculator estimates water use efficiency using harvest yield and effective water supplied. It adjusts irrigation by application efficiency and applies an additional loss fraction.
Notes: 1 mm over 1 m² equals 1 liter. If you use inches, the calculator applies 25.4 mm per inch.
How to Use This Calculator
- Measure harvested yield for your crop and enter it.
- Enter the matching growing area for that harvest period.
- Add irrigation applied from meter logs or container totals.
- Enter effective rainfall depth for the same area and dates.
- Set irrigation efficiency and any additional losses you observe.
- Press Calculate to see WUE, footprint, and area-normalized checks.
For better comparisons, keep crop variety, spacing, and harvest definition consistent across seasons.
Interpreting Your Results
- Higher WUE often indicates good scheduling, healthy roots, and reduced evaporation losses.
- Lower water footprint supports water-saving goals and can reveal overwatering patterns.
- Water per area helps confirm whether irrigation volumes match crop and climate demand.
- Use notes to track mulch, shading, wind, or emitter changes affecting performance.
Improving measurement quality
Accurate water use efficiency starts with clean records. Weigh harvest after removing culls, and keep the same maturity standard each time. Read irrigation meters at the same hour, or total container fills. If rainfall is used, choose effective rainfall that actually infiltrates the bed. Mulch and canopy cover can reduce evaporation, raising efficiency without changing yield.
Understanding the water balance
The calculator combines effective irrigation and rainfall, then reduces that total by losses such as runoff and deep percolation. Drip lines often deliver 80–95% efficiency, while sprinklers may be lower in windy conditions. A 20 m² plot receiving 15 mm rain contributes about 300 liters. When losses are trimmed from 15% to 5%, the same inputs can improve reported efficiency by roughly 12%.
Using benchmarks for decision making
Compare seasons with identical units: kg per cubic meter and liters per kilogram. For leafy greens, small increases in yield can shift results quickly because water volumes are modest. For fruiting crops, irrigation dominates, so improving distribution uniformity matters more. Track water per area (L/m²) to validate that your schedule matches crop demand, then confirm yield density to avoid overwatering low-performing zones.
Interventions that typically raise WUE
Start with delivery: fix leaks, flush filters, and check emitter flow. Improve soil intake using compost, gentle cultivation, and timed irrigation pulses that prevent runoff. Use early-morning watering to reduce evaporative loss. Add shade cloth during heat waves to protect yield quality. If yield is stable, reducing non-beneficial water by 10% usually raises WUE by about 11%.
Planning a repeatable monitoring routine
Set a consistent accounting window, such as weekly or per harvest cycle. Record yield, area, irrigation applied, and rainfall depth. Note system changes, pest pressure, or heat events. Recalculate after adjustments, and archive CSV/PDF reports. Over several cycles, use the trend to justify hardware upgrades, refine scheduling, and communicate water-saving outcomes with clear, auditable metrics. Pair results with taste and size grades to protect market value across harvests.
FAQs
What does WUE mean in this calculator?
Water use efficiency is yield divided by effective water supplied. Effective water includes rainfall and irrigation adjusted for application efficiency and losses. Higher values indicate more yield produced per unit of water.
Why does irrigation efficiency matter?
Efficiency represents how much applied irrigation actually reaches the root zone. Low efficiency can come from wind drift, uneven distribution, or poor pressure control. Adjusting it helps the calculation reflect real plant-available water.
How should I estimate effective rainfall?
Use rainfall that infiltrates your growing area. Subtract runoff from intense storms, and ignore rain that falls when soil is saturated. A practical method is to cap effective rainfall to the soil’s storage between irrigations.
What are ‘additional losses’?
These cover runoff, leaks, deep percolation, and overspray after efficiency is applied. If you notice puddling or drainage below the root zone, increase the loss percentage. If the system is tight and soil absorbs well, lower it.
Can I compare two crops with different areas?
Yes, as long as you enter the correct area and matching yield and water for each crop. Comparing WUE across crops is most useful when quality targets are similar and the accounting period covers the full harvest window.
Which result should I focus on first?
Start with water footprint (L/kg) for quick savings, then confirm WUE (kg/m³) for performance tracking. Use water per area (L/m²) to spot overwatering. Improve delivery and scheduling before changing crop density.