Irrigation water calculator
Irrigation is measured as a depth of water applied, which converts to volume through the area.
mm
L/s
%
mm/day
Run time
21:42:05
- Water required
- 3125.0
- Gross depth to apply
- 31.25 mm
- Water per hectare
- 312.5 m3/ha
- Days until the next irrigation
- 5.00
- Run time in hours
- 21.701
- Seasonal demand over 120 days
- 600 mm
Show the working
- Area = 10
- Water to apply = 25
- System flow rate = 40
- Application efficiency = 80
- Daily evapotranspiration = 5
- Gross depth to apply = 25 / (80/100) = 31.25
- Water required = 10 * 10000 * 31.25 / 1000 = 3125
- liters = 3125 * 1000 = 3 125 000
- Run time in hours = 40 > 0 ? 3 125 000 / 40 / 3600 : 0 = 21.7014
- Run time = 21.7014 * 3600 = 78 125
- Days until the next irrigation = 5 > 0 ? 25 / 5 : 0 = 5
- Water per hectare = 31.25 * 10 = 312.5
- Seasonal demand over 120 days = 5 * 120 = 600
Values are shown to six significant figures here; the arithmetic itself runs on exact fractions and is only rounded where a number is printed.
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The formula
- one millimetre of water over one hectare is exactly 10 cubic metres
- gross depth = net depth / application efficiency
Flood irrigation runs at 50 to 60% efficiency, sprinklers 70 to 85%, and drip 85 to 95%.