Formula used
Area-based demand: Daily net water (L) = area (m²) × net irrigation depth (mm).
Plant-based demand: Daily net water (L) = plant count × litres per plant daily.
Gross demand: Gross water = net water ÷ irrigation efficiency.
Runtime: Runtime (minutes) = cycle water ÷ total flow (L/h) × 60.
Friction loss: Hazen-Williams estimates pressure losses through mainlines and laterals.
How to use this calculator
Choose the area method and enter matching dimensions. Select compatible units before entering each value. The calculator converts measurements into consistent internal units.
Enter crop, emitter, soil, and climate information. Use advanced mode for pressure and pipe calculations. Manufacturer data should override general estimates.
Submit the form to review water demand and runtime. Check warnings before selecting equipment or operating schedules. Confirm final designs with local irrigation guidance.
Example data
| Input | Example | Purpose |
|---|---|---|
| Area | 20 m × 10 m | Defines the irrigated footprint. |
| Crop coefficient | 0.80 | Adjusts reference evapotranspiration. |
| Emitter flow | 2 L/h | Controls system flow and runtime. |
| Soil | Loam | Provides infiltration and storage estimates. |
| Available pressure | 250 kPa | Supports hydraulic adequacy checking. |
Frequently asked questions
How is irrigation runtime calculated?
Runtime divides required cycle water by total emitter flow. The result is converted into minutes for scheduling. Actual field uniformity can change operating time.
What emitter flow rate should I enter?
Use the rated flow from the emitter manufacturer. Confirm the rating at your operating pressure. Worn or blocked emitters may deliver differently.
Can I calculate drip tape systems?
Yes, select the inline dripline layout option. Enter emitter spacing and the tape flow rating. Verify maximum run length with supplier data.
Why does soil infiltration matter?
Water applied faster than infiltration can cause runoff. Lower-flow emitters can reduce this problem. Split cycles also improve soil absorption.
What does irrigation efficiency represent?
Efficiency accounts for system and application losses. Higher efficiency reduces required gross water volume. Use realistic values for your equipment condition.
How many irrigation zones do I need?
The calculator divides total flow by maximum zone flow. It rounds the result upward automatically. Pressure limitations may require additional zones.
Is the pump recommendation a final selection?
No, it estimates flow capacity with a margin. Pump head and performance curves still matter. Confirm selection with the complete hydraulic design.
How accurate is the pressure-loss estimate?
It uses the Hazen-Williams equation and entered pipe data. Fittings and elevation are included separately. Field measurements improve final design accuracy.
Can rainfall reduce irrigation demand?
Yes, effective rainfall is subtracted from calculated crop demand. Only usable rainfall should be included. Excess rainfall should not create negative demand.