Gross Irrigation Depth Calculator

Calculator Inputs

This page uses a single stacked page layout, while the form fields follow a 3-column, 2-column, and 1-column responsive grid.

Calculation method

Choose how the net irrigation depth is obtained.

Depth unit

All depth inputs and outputs use this unit.

Area unit

Used for delivery volume estimation.

Field capacity (%)

Volumetric water content at field capacity.

Permanent wilting point (%)

Volumetric water content at permanent wilting point.

Root zone depth

Active depth of the irrigated root zone.

Management allowed depletion (%)

Percent of available water allowed to deplete.

Direct net irrigation depth

Use this when the net depth is already known.

Effective rainfall

Rainfall that reduces irrigation demand.

Leaching requirement

Extra depth added for salt management.

Application efficiency (%)

Accounts for field application losses.

Distribution uniformity (%)

Optional correction for nonuniform application.

Conveyance efficiency (%)

Accounts for canal or pipeline delivery losses.

Field area

Used to estimate total water delivery volume.

Reset

Formula Used

Available water depth
AW = ((FC − PWP) / 100) × Root Zone Depth

Net irrigation depth from soil depletion
Nd = AW × (MAD / 100)

Adjusted net depth
And = max(Nd − Effective Rainfall, 0) + Leaching Requirement

Gross field depth
Gfd = And ÷ ((Application Efficiency / 100) × (Distribution Uniformity / 100))

Gross project depth
Gpd = Gfd ÷ (Conveyance Efficiency / 100)

Required water volume
Volume (m³) = Gross Project Depth (mm) × Area (ha) × 10

In direct mode, the entered net irrigation depth replaces the soil-depletion equation.

How to Use This Calculator

Choose whether you want to calculate from soil depletion or direct net depth.
Select the depth unit and area unit.
Enter soil values when using depletion mode, or enter direct net depth.
Add rainfall, leaching, application efficiency, conveyance efficiency, and distribution uniformity.
Enter field area to estimate total delivery volume.
Click the calculate button to display the result above the form.
Review the chart, result table, and export the report as CSV or PDF.

Example Data Table

Parameter	Example Value	Notes
Calculation method	Soil moisture depletion	Uses soil storage and allowed depletion.
Field capacity	32%	Volumetric soil water at field capacity.
Permanent wilting point	16%	Lower limit for plant extraction.
Root zone depth	600 mm	Active crop root depth.
Management allowed depletion	50%	Refill half of available soil water.
Effective rainfall	12 mm	Reduces irrigation demand.
Leaching requirement	8 mm	Added for salinity control.
Application efficiency	78%	Field delivery performance.
Distribution uniformity	90%	Corrects for uneven application.
Conveyance efficiency	92%	Canal or pipe delivery performance.
Field area	2.5 ha	Total irrigated area.
Gross project depth	68.13 mm	Calculated example result.
Required water volume	1,703.20 m³	Total delivery required for the field.

FAQs

1. What is gross irrigation depth?

Gross irrigation depth is the water depth that must be delivered to the field or project after accounting for field losses, conveyance losses, and any additional leaching requirement.

2. Why is gross depth larger than net depth?

Net depth is the amount needed in the crop root zone. Gross depth is larger because some water is lost during delivery, nonuniform application, runoff, evaporation, and deep percolation.

3. When should I use soil depletion mode?

Use soil depletion mode when you know field capacity, permanent wilting point, root depth, and allowed depletion. It is useful for irrigation scheduling based on soil water storage.

4. When should I use direct net depth mode?

Use direct mode when the net irrigation requirement has already been calculated elsewhere. The calculator then applies rainfall, leaching, and efficiency corrections to estimate the gross depth.

5. What does effective rainfall mean?

Effective rainfall is the portion of rainfall stored in the crop root zone and available to plants. It reduces the irrigation depth that must be supplied artificially.

6. Why include distribution uniformity?

Distribution uniformity helps correct for uneven application across the field. Poor uniformity usually increases the gross depth needed so the driest zones still receive enough water.

7. What is leaching requirement?

Leaching requirement is extra water applied to move salts below the active root zone. It is often important in arid regions or where irrigation water has higher salinity.

8. Does this calculator estimate total water volume?

Yes. After computing the gross project depth, it multiplies that depth by the field area to estimate total delivery volume in cubic meters and liters.