Calculated Results
Complete the form to calculate distribution uniformity.
| Point | Measurement | Rank | Difference | % of average | Low group | Outlier |
|---|
Interpretation
Possible causes and actions
Catch-can or emitter heatmap
Comparison Results
Formula used
Low-quarter distribution uniformity
DULQ = (Average of the lowest quarter ÷ Average of all measurements) × 100
Christiansen uniformity coefficient
CU = 100 × [1 − Σ|xᵢ − x̄| ÷ (n × x̄)]
The calculator first validates every measurement. It ranks valid readings from lowest to highest. The selected sample rule determines how many readings enter the lower group when the sample count is not divisible evenly.
How to use this calculator
- Select the irrigation system and measurement unit.
- Choose the preferred uniformity method.
- Enter catch-can depths, collected volumes, or emitter flows.
- Add optional pressures, test duration, catch area, and runtime details.
- Calculate the results and inspect low-output points.
- Review charts, diagnostics, and runtime guidance.
- Export the audit as CSV or PDF.
Example data
| Point | Collected depth | Pressure | Comment |
|---|---|---|---|
| A1 | 12.4 mm | 280 kPa | Normal |
| A2 | 13.1 mm | 285 kPa | Normal |
| B1 | 9.7 mm | 245 kPa | Inspect nozzle |
| B2 | 14.0 mm | 290 kPa | Normal |
Understanding distribution uniformity
Distribution uniformity describes how evenly irrigation water reaches the measured area. A high percentage means the low-output locations remain reasonably close to the overall average. A low result indicates that some locations receive much less water.
Catch-can tests work well for spray and rotor systems. Place identical containers in a planned grid, run the system for a fixed time, and measure each collected depth or volume. Avoid changing container size or test duration during one test.
Emitter tests use measured discharge from individual outlets. Sample points should represent the beginning, middle, and end of laterals. Include high and low elevations when pressure changes across the field.
Poor uniformity may result from clogged nozzles, worn emitters, pressure loss, wind, leaks, spacing errors, or mixed components. The calculator highlights patterns but cannot confirm the physical cause. Inspect the system before making expensive changes.
Runtime adjustment can compensate for low-output areas, but longer operation may overwater better-performing locations. Use the result with soil intake, root depth, application efficiency, weather, and crop demand. A repair often saves more water than extra runtime.
Comparison mode helps document maintenance results. Test under similar pressure, wind, layout, and duration whenever possible. Large differences in test conditions can distort the apparent improvement.
Frequently asked questions
What is low-quarter distribution uniformity?
It compares the average of the lowest quarter of readings with the overall average.
How many measurements are required?
The calculator requires at least four. More well-placed measurements usually provide a stronger field assessment.
Can I enter volumes instead of depths?
Yes. Use identical catch cans, or provide the catch opening area for depth and application-rate calculations.
What happens when the count is not divisible by four?
Choose whether the lower-group count rounds up, down, or to the nearest whole number.
Does a higher DU always mean better irrigation?
It indicates more even distribution, but it does not measure every loss, scheduling error, or agronomic requirement.
Why include pressure readings?
Pressure differences can reveal hydraulic patterns that may explain uneven sprinkler or emitter output.
Can wind affect sprinkler tests?
Yes. Strong or shifting wind can move droplets and reduce repeatability.
How is Christiansen uniformity different?
It considers the absolute deviation of every reading from the overall average.
Can I compare two tests?
Yes. Comparison mode reports changes in uniformity, average output, variability, and estimated runtime.
Is the runtime recommendation exact?
No. It is a planning estimate and should be checked against soil, crop, weather, and equipment conditions.