Regulated Deficit Irrigation ET Fraction Calculator
Conditional gross irrigation depth from reference ET, caller crop coefficient and deficit fraction; not an irrigation prescription.
Description
Calculate conditional gross irrigation depth from ET, crop, retained deficit and efficiency factors.
A conditional irrigation estimate can combine reference evapotranspiration, a crop coefficient, a chosen deficit fraction and delivery efficiency. This tool applies those supplied factors without choosing a deficit-irrigation strategy.
When to use this tool
Calculate conditional gross irrigation depth from ET, crop, retained deficit and efficiency factors. Use it when the input measurements and conventions below match the operation you need.
- Prepare referenceEtMm, cropCoefficient, deficitFraction, deliveryEfficiency, respecting the measurement basis and boundaries below.
- Compare the worked example with your intended operation before reusing its result.
How to use the tool and how it works
- Enter every field in the input table using the stated units and exact supported selector spelling where applicable.
- Run the tool. Correct input errors before interpreting an output.
- Read the result fields below; use accompanying flags and the stated sign, boundary or model convention when interpreting a number.
Reference ET and crop coefficient must be nonnegative; deficitFraction from zero to one; deliveryEfficiency greater than zero and no greater than one. grossIrrigationMm equals referenceEtMm times cropCoefficient times deficitFraction divided by deliveryEfficiency.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| referenceEtMm | Reference et mm. Millimeters. | Finite number; zero or greater |
| cropCoefficient | Crop coefficient. | Finite number; zero or greater |
| deficitFraction | Deficit fraction. Fractional units; 0.2 means 20%. | Finite number; from zero to one inclusive |
| deliveryEfficiency | Delivery efficiency. | Finite number; greater than zero; from zero to one inclusive |
| Output field | Interpretation |
|---|---|
| result | Object containing the following named result fields. |
| result.grossIrrigationMm | Gross irrigation mm; use the stated units and sign convention. |
{
"input": {
"referenceEtMm": 10,
"cropCoefficient": 0.8,
"deficitFraction": 0.5,
"deliveryEfficiency": 0.8
},
"output": {
"result": {
"grossIrrigationMm": 5
}
}
}Limitations and assumptions
- deficitFraction is the fraction retained in the calculation: 0.8 applies 80%, rather than subtracting 80%. Rainfall, stored soil water, salinity, stress targets and scheduling are not modeled.
- Every declared field is required and unexpected fields are rejected. Numeric inputs must be finite; input errors are distinct from a valid false result or an explicitly qualified output.
- Extremely large inputs and nonfinite or excessively large outputs are rejected. List positions reported by the tool use zero-based indices unless stated otherwise.
Alternative or Complementary methods
Compare the result with actual block measurements, soil or crop observations and the declared management basis. Use a site-specific model when effects omitted here materially affect the decision. Compare the scope of the nearby tools below before substituting one.
References
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