An irrigation timer measures minutes, not the litres delivered to each plant. A simple container test can show whether a line distributes water evenly and whether the labelled emitter rate matches what happens in your garden.
From the Namibian discussions
The Namibian collection includes drip-irrigation demonstrations and advice about short watering periods under shade cloth. These are useful starting points, but a fixed number of minutes cannot fit every pressure, emitter, soil and season. Measure your own system before adopting a schedule.
Prepare a fair test
- Operate the zone normally and allow flow to stabilise. Keep the usual valves and other zones in their normal positions.
- Place equal containers beneath selected emitters near the supply, midway and at the far end. Include high and low ground if relevant.
- Collect water for exactly the same time at each location. Label each result in millilitres or litres.
- Repeat an unexpected result before adjusting anything.
Convert the result
Litres collected × 60 ÷ minutes gives litres per hour. For example, 0.5 litres in 15 minutes is 2 litres per hour. Two such emitters running for 30 minutes supply about 2 litres together. This is delivered water, not proof that the whole root zone received the right amount.
Look at the weakest part
University of Maryland guidance describes checking distribution using the lowest quarter of readings. With 16 containers, average the four lowest measurements and divide by the average of all 16, then multiply by 100. A low result directs attention to pressure, layout or clogging. Do not hide dry plants by overwatering the rest.
Connect flow to soil observations
Inspect wetting depth and spread after irrigation without cutting major roots. Record plant stage, soil type and recent rain. Change the schedule gradually and check the response; identical litres may spread very differently in sand and heavier soil. Keep the calculation sheet beside the irrigation controls.
Namibian climate and microclimate
Wind, heat, coastal humidity and shade affect demand. Borehole or solar-pump pressure may change through a run. Test under typical conditions and repeat after repairs or seasonal changes rather than assuming last year’s measurements still apply.
Your first practical step
Measure four contrasting locations today, then expand to 16 if you want a useful uniformity comparison.
Watch and adapt
Watch videoWatch: Drip Irrigation Problems and Solutions
Publisher: University of Arkansas Cooperative Extension
Country and context: USA; Arkansas extension context.
Episode 5 of the drip-irrigation series. Use the metric container calculation in this guide for your own measurements.
Compare the diagnostic approach with your timed container readings. Irrigation demand still depends on your crop and microclimate.
Keep exploring
- Drip Irrigation
- Blocked drip lines: diagnose the blockage before cleaning
- Garden weather records: learn what happens at your own site
Sources and further reading
Have you tried this in Namibia? Share the site conditions, method and result—including what did not work—with the Living Earth community. Local observations help the next person adapt the idea.