Rice Water Requirement Calculator
Work out the seasonal and per-irrigation water requirement of rice (awd water-saving) (FAO-56 ETc = ET₀ × Kc, peak Kc 1.05) for your field, climate, soil and irrigation method.
AWD is safe once the crop is established: let ponded water recede until the water table is ~15 cm below the surface (a simple field tube shows this), then re-flood ~5 cm. Keep continuous flooding only during flowering.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Farmers and irrigation planners use the free Rice Water Requirement Calculator to turn the FAO-56 crop coefficients for rice (awd water-saving) into a real seasonal water volume and an irrigation interval for their own field — no agronomy tables, works offline.
About Rice Water Requirement Calculator
Alternate wetting and drying (AWD) cuts paddy water 15–30% by letting the field dry to ~15 cm below surface before re-flooding — modelled here with reduced effective Kc. This calculator uses the FAO-56 method — crop evapotranspiration ETc = ET₀ × Kc — with rice (awd water-saving)'s own crop coefficients (Kc 0.95 initial, 1.05 mid-season, 0.85 late) across a 130-day season. Pick your climate band (which sets reference ET₀), irrigation method (drip, sprinkler, pivot or surface — each with its own efficiency) and soil texture, and it returns the seasonal water need in cubic metres, the peak daily demand, the net depth per irrigation and how many days to wait between irrigations.
How to use Rice Water Requirement Calculator
- 1Enter your field area and choose the climate band matching your season.
- 2Select your irrigation method and soil texture.
- 3Read the seasonal water volume, peak daily demand and irrigation interval, then follow the scheduling note.
Why use Rice Water Requirement Calculator?
- ✓Uses rice (awd water-saving)'s real FAO-56 Kc curve, not a flat factor
- ✓Accounts for drip / sprinkler / pivot / surface efficiency
- ✓Gives seasonal volume, peak daily need and an irrigation interval
- ✓Free, instant and fully in-browser — works offline in the field
Frequently asked questions
How much water does rice (awd water-saving) need?+
Alternate wetting and drying (AWD) cuts paddy water 15–30% by letting the field dry to ~15 cm below surface before re-flooding — modelled here with reduced effective Kc. The exact figure depends on climate and season length; this tool sums ET₀ × Kc across the crop's 130-day growth stages for your conditions.
How does AWD save water in rice?+
By not keeping the field continuously ponded. Letting it dry to ~15 cm below the surface between irrigations cuts seepage and percolation losses — the bulk of rice water use — saving 15–30% with no yield loss on suitable soils.
When should I NOT dry the field under AWD?+
Keep the field flooded during the flowering (heading) period, which is sensitive to water stress, and avoid AWD on very sandy soils that drain too fast or where weeds explode. Otherwise apply AWD from establishment to maturity.
What is ET₀ and Kc?+
ET₀ (reference evapotranspiration) is how fast a standard grass surface loses water in your climate. Kc (crop coefficient) scales it to a specific crop and growth stage. Crop water use ETc = ET₀ × Kc — the basis of FAO-56 irrigation scheduling.
Is this calculator free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline in the field and your data never leaves the device.
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