Overview
ISO 11545:2009 - "Agricultural irrigation equipment - Centre‑pivot and moving lateral irrigation machines with sprayer or sprinkler nozzles - Determination of uniformity of water distribution" defines an in‑field test method to measure how uniformly water is applied by centre‑pivot and moving lateral irrigation machines. The standard specifies the test setup, collector design and layout, environmental and operational limits, data handling, and the calculation of the coefficient of uniformity (modified Heermann and Hein method). It applies where the water application device is more than 1.5 m above the soil surface and where adjacent device patterns overlap; it excludes certain corner‑arm configurations.
Key topics and technical requirements
- Applicability: Centre‑pivot and moving lateral systems with overlapping nozzle patterns; device height > 1.5 m.
- Collectors: Identical receptacles with circular openings (min. 85 mm diameter), depth ≥ twice maximum expected catch (≥ 150 mm recommended); entrance level and placement rules to avoid splash and obstructions.
- Collector layout: Lines perpendicular (pivot) or parallel (moving lateral) to machine travel; maximum line separation 50 m; spacing requirements tied to sprinkler wetted radius; recommended offset between adjacent lines.
- Wind and microclimate: Wind measured at 2 m height with anemometer (threshold ≤ 0.3 m/s; accuracy ±10%). Test reliability decreases above 1 m/s and is not valid above 5 m/s unless limitations are acknowledged. Record wind speed/direction at ≤15 min intervals.
- Evaporation control: Prefer tests during low‑evaporation periods; use control collectors to estimate evaporation rate and adjust collected volumes; methods like suppressants or special collectors may be used and must be recorded.
- Operational conditions: Maintain test pressure within ±5% of agreed test pressure (pressure instrument accuracy ±2%); deliver average application depth ≥15 mm unless otherwise specified; measurement devices accurate to ±3%.
- Data handling: Exclude obviously erroneous points (≤3% of measurements) with reasons recorded; inner 20% of centre‑pivot collectors may be excluded by agreement; exclude observations beyond effective radius/length.
- Calculations & reporting: Coefficient of uniformity calculated using the modified Heermann and Hein formula; Annex A includes sample data sheets and test report forms.
Applications and users
ISO 11545:2009 is used by:
- Irrigation equipment manufacturers for product verification and design validation
- Irrigation consultants and testing laboratories to assess field performance and uniformity
- Agronomists and farm managers to optimize irrigation scheduling and efficiency
- Procurement bodies and regulators requiring standardized performance measurement
Practical uses include commissioning new sprinkler packages, troubleshooting non‑uniform application, comparing nozzle packages, and documenting performance for contracts or certification.
Related guidance
For comprehensive irrigation system assessment, pair ISO 11545:2009 testing with site‑specific agronomic and hydrological evaluations and other ISO/TC 23 guidance on irrigation and drainage equipment.