Irrigation Calculator — Daily Water Need & Run Time | LandLens
Calculate daily crop water requirements using ET\u2080 and crop coefficients. Get total volume, system run time, and efficiency for drip, sprinkler, or flood irrigation.
Results
Water Needed
4.5 mm/day
ET₀ 4.5 × Kc 1
Water Needed
crop demand
Water to Apply
at 92% efficiency
Run Time
97.8 h
Flow Rate
500 L/hr
92% system efficiency — 8% lost to evaporation & runoff
How Crop Water Requirement Is Calculated
Daily crop water requirement combines reference evapotranspiration (ET₀) with a crop-specific coefficient (Kc) that adjusts for canopy cover and growth stage.
ETc (mm/day) = ET₀ × Kc
Volume (L/day) = ETc × Area (m²)
Multiply the daily water depth by your field area to get total volume, then divide by your irrigation system's flow rate and efficiency to get run time.
Irrigation System Efficiency
| System | Efficiency | Main losses |
|---|---|---|
| Drip irrigation | 90–95% | Dripper variation, minor evaporation |
| Sprinkler | 75–85% | Wind drift, evaporation |
| Surface / flood | 50–60% | Runoff, deep percolation |
Common Use Cases
Drip Irrigation
Calculate water volume for precision micro-irrigation systems
Center-Pivot Systems
Plan water application for circular field irrigation
Greenhouse Growing
Monitor water needs for controlled environment crops
Landscape Irrigation
Schedule watering for nurseries, turf farms, and gardens
Water Conservation
Reduce consumption while maintaining yield through proper scheduling
System Sizing
Determine pump and pipe capacity needs before equipment purchase
Frequently Asked Questions
How is crop water requirement calculated?
Crop water requirement = ET₀ × Kc, where ET₀ is reference evapotranspiration and Kc is the crop coefficient. Multiply by field area to get total volume.
What is ET₀ in irrigation?
ET₀ is the amount of water evaporated from a standardized grass surface under your climate. It accounts for temperature, humidity, wind, and solar radiation.
What is a crop coefficient (Kc)?
Kc adjusts ET₀ for your specific crop and growth stage. Values come from FAO standards. Grass Kc ≈ 1.0, corn mid-season Kc ≈ 1.2.
Why does applied water exceed needed water?
No irrigation system is 100% efficient. Drip irrigation loses ~8% to dripper variation. Sprinklers lose ~20% to wind drift and evaporation. Surface flooding loses 40%+.
Need to Measure Field Area?
Use LandLens to measure your field boundaries with GPS precision.
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