Irrigation Scheduling Calculator
Sizing tells you the pump to buy. Scheduling tells you when to turn it on and for how long.
The irrigation sizing calculator picks a pump. This one turns daily crop demand into a when and how long plan: the net use each day, the soil's usable water, how many days you can go between irrigations, and the run time each event needs.
Irrigation scheduling calculator
Daily replacement, soil water buffer, interval and run time.
Peak full canopy 6–9 mm/day
Use a conservative dry-season figure
From the sizing calculator
Drip 90 · micro-sprinkler 80–85 · furrow 55–65
Soil water reservoir
Loam ~140 · clay ~180 · sand 60–90
Banana roots feed mostly in the top 0.3–0.5 m
How much of the stored water you let the crop use before watering
The formulas#
Net daily use (mm/day) = ETc − effective rainfall
Gross daily depth (mm) = net daily use ÷ application efficiency
Volume per day (m³) = gross daily depth × area (ha) × 10
Run time per day (h) = volume per day ÷ system flow (m³/h)
Readily available water = WHC (mm/m) × root depth (m) × MAD (%)
Suggested interval (d) = RAW ÷ net daily use
Depth per irrigation = net daily use × interval (= RAW)
Volume per irrigation = depth ÷ efficiency × area × 10
Run time per irrigation = volume per irrigation ÷ system flowOne millimetre of water over one hectare is exactly 10 m³ — that single fact makes the whole schedule countable.
Worked example#
2 ha, ETc 6 mm/day, 3 mm/day rain, 85% efficiency, 20 m³/h, 12 h/day,
WHC 120 mm/m, root 0.4 m, MAD 40%:
Net daily use = 6 − 3 = 3.0 mm/day
Gross daily = 3.0 ÷ 0.85 = 3.5 mm/day
Volume per day = 3.5 × 2 × 10 = 70.6 m³/day
Run time/day = 70.6 ÷ 20 = 3.5 h/day
RAW = 120 × 0.4 × 0.40 = 19.2 mm
Interval = 19.2 ÷ 3.0 = 6.4 days
Volume/event = 19.2 ÷ 0.85 × 2 × 10 = 451.8 m³
Run time/event = 451.8 ÷ 20 = 22.6 h (≈ 3.5 h/day)You can either spread that as a short daily pulse or as a heavy soak every six days. Both deliver the same water; the daily pulse keeps the topsoil closer to field capacity and suits banana's shallow roots.
Reading the results#
| Output | Why it matters |
|---|---|
| Net daily use | What the crop actually extracts each day after rain |
| Gross daily depth | Only if you also allow for efficiency losses |
| Run time per day | Whether your pump and hours are realistic |
| Readily available water | The soil buffer between irrigations |
| Suggested interval | How many days you can safely wait |
| Depth & volume per event | The setting for a soak-and-dry schedule |
| Weekly volume | Source draw and energy budgeting |
Next steps#
- Size the system first: Irrigation sizing calculator.
- Understand the demand curve by stage: Water management.
- Install and maintain it: Setting up irrigation.
- Handle the dry spells: Drought and extreme weather.