SOIL WATER

Root Zone Soil Water Budget Calculator

Track a simple daily available-water bucket using entered soil fractions, root depth, effective rainfall, net irrigation and ET.

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01 / INPUT

Constant modeled root-zone depth

Volumetric water at field capacity (%)

Volumetric water at wilting-point reference (%)

Initial depletion from available-water capacity (mm)

Entered depletion trigger fraction of capacity (%)

Consecutive daily rows: date | effective rain mm | net irrigation mm | ET mm

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Result

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Calculation steps

Work through one step at a time or reveal the complete calculation. The steps use your current inputs.

How to calculate

Convert the soil-water fraction difference and root depth into available-water capacity. Add each day’s inputs, remove bucket overflow, then subtract ET and track depletion.

Capacity=(field fraction−wilting fraction)×root depth mm; end=max(0,min(capacity,start+rain+irrigation)−ET)

Worked example

30 cm root depth with field capacity 30% and wilting reference 10% gives 60 mm available-water capacity. Starting 20 mm depleted leaves 40 mm; a dry 5 mm ET day ends at 35 mm.

Assumptions and input details

An entered scenario with constant soil fractions/root depth, not a soil-type lookup or crop advisory. Daily order is inputs first, drainage second, ET last; another event order can differ. Effective rain and net irrigation already exclude losses outside this bucket. Capacity is water above the wilting reference, not total soil water. Unmet modeled ET is reported if the bucket empties. No infiltration limit, capillary flow, root growth, stress-response model or automatic irrigation schedule. Up to 366 consecutive days.

Unit definitions

Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.

Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.

Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.

NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions

Using this calculator

Can I enter my own problem?

Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.

Are the results exact?

Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.

Is my input uploaded?

The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.

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