Irrigation tank size calculator
An irrigation tank’s size depends on two things: the water the crop takes on the hottest day, and how much of it your source can give in the hours you water. The tool works out a reserve for when the source stops and the gap within the day, and suggests a galvanised steel tank for the larger of the two. It leaves out the water at the top and bottom that you can’t use.
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A worked example
25 decares of soilless strawberry in Serik. The hottest day needs 5 mm. The well gives 8 tonnes an hour and can run 20 hours a day; watering takes 10 hours. One day of reserve is wanted.
- Water on the hottest day 5 mm × 25 decares = 125 tonnes
- One day of reserve 125 × 1 = 125 tonnes
- Gap within the day 125 − 8 × 10 = 45 tonnes; the well gives 8 × 20 = 160 tonnes a day, so the tank refills at night
- Tank the larger is 125 tonnes; a Ø 9.2 × 2.4 m galvanised tank, 132 tonnes usable, 158 tonnes gross
- Time to fill 132 ÷ 8 = 16.5 hours
[The example’s numbers await Perge’s check.]
How it is worked out
Water on the hottest day is the need in mm times the area: 1 mm is 1 tonne per decare. The reserve is that times the days you choose; it covers a power cut, a pump fault or the canal’s turn.
The gap within the day is the water the crop draws in the watering hours, less what the source gives in those same hours. The tank refills it in the hours you don’t water. If the source gives less in a whole day than the crop needs, the tank runs lower each day; the tool warns you when that happens.
The tank is sized for the larger of the reserve and the gap. Usable volume leaves 30 cm empty at the top and 10 cm below the outlet. The sizes are typical for corrugated galvanised tanks built from 1.2 m rings and 2.4 m panels. The tool suggests a low tank first, and goes one ring higher when the diameter passes four times the height.
Questions
How big should an irrigation tank be?
At least as big as the water your source can’t keep up with in the watering hours on the hottest day. If you want to keep watering when the source stops, add a day’s need. For example, 25 decares of soilless strawberry need about 125 tonnes on the hottest day; for one day of reserve, pick a tank with more than 125 tonnes usable.
What size tank does one decare need?
In Antalya, a decare takes 4 to 9 tonnes on the hottest day, by crop. Soilless strawberry in a greenhouse takes about 5 tonnes; open-field tomato close to 9. For one day of reserve, plan that much usable volume per decare.
How do I work out a round steel tank’s volume?
Volume = 3.14 × diameter × diameter ÷ 4 × height. A tank 10 m across and 3 m high holds about 236 tonnes gross. Take off the empty space at the top and the water below the outlet, and 2.6 m of depth gives about 204 tonnes usable.
Does a tank help if my well is too weak?
If the well gives enough over the whole day but not in the watering hours, yes: the well fills the tank at night and the pump waters from the tank by day. If the well’s whole day is less than the crop needs, a tank only gets you through a few hot days; then you need more water or a smaller planted area.
How high should the tank be?
A low tank is easier to build but takes more ground; a high tank fits a small plot. The tool works out tanks of two, three and four rings (2.4, 3.6 and 4.8 m) and shows the diameter each height needs. We make the choice with you, by the site and its ground.
How do I pick a pump when I water from a tank?
The tank sits between the well and the watering, so the pump is sized for one zone’s flow, not for the well. Its pressure is the pipe losses, the height difference and what the emitters need, added up. The pump tool does this sum.