How is crop water requirement calculated?

Crop water requirement = ET₀ × Kc, where ET₀ is the reference evapotranspiration (mm/day) for your climate and Kc is the FAO-56 crop coefficient. The result is the daily water depth the crop needs. Multiply by field area (in m²) to get total litres (1 mm over 1 m² = 1 litre).

What is ET₀ in irrigation?

ET₀ (reference evapotranspiration) is the amount of water evaporated from a standardised short grass surface under your local climate conditions, expressed in mm/day. It accounts for temperature, humidity, wind, and solar radiation. Arid regions typically see 7–9 mm/day while temperate climates see 2–4 mm/day.

What is a crop coefficient (Kc)?

The crop coefficient (Kc) adjusts ET₀ for the specific crop type and growth stage. Values come from FAO Irrigation and Drainage Paper 56. Grass has Kc ≈1.0, maize mid-season Kc ≈1.2, and tomatoes mid-season Kc ≈1.15.

Why does applied water exceed needed water?

No irrigation system is 100% efficient. Drip irrigation loses ≈8% to dripper variation and soil wetting losses. Sprinklers lose ≈20% to wind drift and evaporation. Surface flooding loses 40% or more to runoff and deep percolation. The calculator automatically inflates the applied volume to account for these losses.

How do I calculate irrigation run time?

Run time (hours) = Total volume to apply (litres) ÷ System flow rate (litres/hour). Enter your pump or system flow rate in the calculator and it computes the run time automatically.

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.

气候 / ET₀

气候区

作物

田块面积

≈ 10,000 m²

在地图上测量

灌溉系统

系统类型

流量

L/hr

结果

所需水量

4.5 mm/day

ET₀ 4.5 × Kc 1

所需水量

crop demand

45,000 L

需施用水量

at 92% efficiency

48,913 L

运行时间

97.8 h

流量

500 L/hr

92% system efficiency — 8% lost to evaporation & runoff

作物需水量如何计算

每日作物需水量结合了参考蒸散量(ET₀)与针对冠层覆盖和生长阶段进行调整的作物特定系数(Kc)。

ETc(毫米/天)= ET₀ × Kc

体积(升/天)= ETc × 面积(平方米)

将每日水深乘以你的田块面积以获得总体积,然后除以你灌溉系统的流量和效率以得出运行时间。

灌溉系统效率

System	Efficiency	Main losses
滴灌	90–95%	滴头差异、轻微蒸发
喷灌	75–85%	风力漂移、蒸发
地面 / 漫灌	50–60%	径流、深层渗漏

常见用例

滴灌

计算精准微灌系统所需的水量

中心支轴系统

规划圆形田块灌溉的用水方案

温室种植

监测受控环境作物的需水量

景观灌溉

为苗圃、草皮农场和花园安排浇水计划

节水

通过合理调度在保持产量的同时减少用水量

系统选型

在购买设备前确定水泵和管道的容量需求

常见问题

作物需水量是如何计算的?

作物需水量 = ET₀ × Kc,其中 ET₀ 为参考蒸散量,Kc 为作物系数。乘以田块面积即可得出总体积。

灌溉中的 ET₀ 是什么?

ET₀ 是在你所在气候条件下,标准化草地表面蒸发的水量。它考虑了温度、湿度、风力和太阳辐射。

什么是作物系数(Kc)?

Kc 根据你的特定作物和生长阶段调整 ET₀。数值来源于 FAO 标准。草地 Kc ≈ 1.0,玉米生长中期 Kc ≈ 1.2。

为什么施用水量会超过所需水量?

没有任何灌溉系统能达到 100% 的效率。滴灌因滴头差异损失约 8%。喷灌因风力漂移和蒸发损失约 20%。地面漫灌损失超过 40%。

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