FIELD TOOL GUIDE · Irrigation design
Drip-emitter performance calculator
Evaluate measured emitter discharge, Christiansen uniformity, low-quarter field EU and sample variability.
Method: Measured CU · EU · CV · q
Open this calculator →Inputs and units
Use measurements representative of your field, crop or irrigation system. The values below are illustrative examples.
| Input | Unit | Example value |
|---|---|---|
| Measurement type | Dimensionless / category | Measured discharge (L/h) |
| One measurement per emitter | L/h or L, according to measurement type | 1.80, 1.90, 2.00, 2.10, 1.95, 2.05, 1.85, 2.15, 1.90, 2.00, 2.10, 1.95, 1.85, 2.05, 2.00, 1.90 |
| Common collection duration (volume mode only) | min | 10.000 |
One measurement per emitter: Use a decimal point. Keep zero observations. Enter 4–2000 values.
Worked example
These are calculated demonstration values from the existing tool, not measured field results or a site-specific recommendation.
| Calculated quantity | Example result | Unit |
|---|---|---|
| Mean emitter discharge q̄ | 1.972 | L/h |
| Christiansen uniformity CU | 95.721 | % |
| Field EU / low-quarter DU | 93.819 | % |
| Sample coefficient of variation CV | 0.05153 | fraction |
| Sample CV | 5.153 | % |
| Sample standard deviation s | 0.102 | L/h |
| Low-quarter mean discharge | 1.850 | L/h |
| Minimum observed discharge | 1.800 | L/h |
| Maximum observed discharge | 2.150 | L/h |
| Observed discharge variation | 16.279 | % |
| Measured emitters | 16 | count |
Observed sample performance at the measurement conditions. Uniformity does not establish application efficiency or diagnose the cause of non-uniformity.
The sample CV includes field pressure differences, clogging, wear and measurement error. It is not the manufacturing CV and is not substituted into a design-EU equation.
Field EU and low-quarter DU use the same 100 × low-quarter mean / overall mean definition here. They are not two independent indicators.
Use representative, equally weighted emitters, one operating condition, and equal collection times. Unequal represented areas or durations require a different weighting scheme.
This small sample is suitable for checking the arithmetic but may not represent a complete irrigation zone. The cited IFAS field procedure recommends at least 18 distributed measurement points.
Assumptions and limitations
- Use at least four representative, equally weighted observations under the same operating condition. Include measured zero flows; do not silently discard blocked emitters.
- Enter measured discharges in L/h, or equal-duration collected volumes in litres. Use a decimal point and separate observations with spaces, commas, semicolons or new lines.
- The exact lowest-quarter mean uses fractional boundary weighting when n is not divisible by four. Sample CV is distinct from manufacturer test CV. No design EU or performance rating is inferred.
Use your measurements in this calculator →
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Related guides
Sources
Field EU definition in FAO irrigation-system performance guidance; Christiansen mean absolute-deviation CU; sample standard deviation uses n − 1.