Siphon Tube Irrigation & Flow per Tube & Set Volume

It is a surface-irrigation method where short curved tubes draw water over the wall of a field channel into the furrows, without cutting or breaching the bund. Each tube is primed to start the siphon, and water then flows by gravity from the higher channel into the lower furrow as long as the head difference lasts. It is simple, cheap and gives even control of furrow flow.

It uses the orifice equation Q = Cd · A · √(2gH), where Cd is the discharge coefficient (about 0.6–0.65), A is the tube's cross-sectional area, g is gravity and H is the head — the height of water in the channel above the furrow outlet. Bigger tubes and more head give more flow. Multiply by the number of tubes for the total set flow.

The head is the vertical difference between the water level in the channel and the discharge end of the tube. It is the driving force of the siphon: more head means faster flow through each tube. Because flow rises with the square root of head, doubling the head increases flow by about 40%, not 100%.

Flow scales with the tube's cross-sectional area, which goes up with the square of the diameter, so a small increase in diameter is a large increase in flow. A 50 mm tube delivers roughly four times the flow of a 25 mm tube at the same head. Choose the size to match the furrow length and soil intake.

Run as many as deliver a non-erosive stream to each furrow without overtopping it, matched to the flow your channel can hold. The total set flow should advance water down the furrows in a reasonable time, then be cut back. The tool's total flow helps you balance tubes against channel capacity.

Submerge the whole tube in the channel to fill it with water and expel the air, cap or block the discharge end, lift it over the bund and release it into the furrow so the water column starts the siphon. Once flowing, it continues on its own. Tubes that lose prime have sucked air — re-submerge and restart.

Long enough for water to reach the furrow end and infiltrate to the root zone, then stop to avoid deep percolation and runoff. The set time depends on furrow length, slope, soil intake and the flow you set. The tool reports water per tube and per set so you can match the volume to the soil's needs.

Yes — enter the tube diameter in millimetres, the head in centimetres and the set time in your units, for any number of tubes. The flow and volume outputs apply to whatever crop and furrow layout you irrigate; just feed the water-per-set figure into your field water plan.

They are sound planning estimates from the orifice equation. The real discharge coefficient varies with tube shape, entry condition and how clean the tube is, and the head changes as the channel level falls. Calibrate by timing how long a tube takes to fill a known bucket, and adjust your flow against the field.

The water-per-set figure is the depth and volume you apply each irrigation, which feeds straight into furrow design and your water budget. See the Furrow Irrigation, Channel Flow and Pump Run Time calculators to size the furrows, the supply channel and the pump that fills it.