How to estimate water use for irrigation
Flow in litres per minute is multiplied by the length of a session and the number of sessions per month. Litres are converted to cubic metres and multiplied by the water price.
Formula
Litres per month = flow (L/min) × minutes per session × sessions per month
Volume (m³) = litres ÷ 1,000; cost = volume × price per m³
Worked example
12 L/min × 30 min × 20 sessions = 7,200 L, or 7.2 m³ per month.
At €4/m³, the calculated cost is 7.2 × 4 = €28.80. These figures illustrate the method; they are not a recommended watering schedule.
Assumptions and limits
- Flow and session length are assumed to stay constant. Estimate circuits with different settings separately, then add their water use.
- The tool does not determine plant water requirements from soil or weather. Fixed water charges are not added to the entered price per m³.
Common questions
How can I estimate the actual flow rate?
Time how long it takes to fill a container of known volume, then divide litres by minutes. For example, 6 litres in 30 seconds is 12 L/min. Measure under the conditions in which you will use the system.
Should I enter sessions per week or per month?
Enter the total sessions for the month you are estimating. Use the actual or planned number; multiplying a weekly frequency by four may not match that month’s calendar.