A water-level sensor for the paddy field tube
It sits in the same perforated tube IRRI recommends for Alternate Wetting and Drying, reads the water level, and reports it by radio, so nobody has to walk out and look.
What it does
AWD depends on one number: how far the water is above or below the soil surface. IRRI’s method uses a perforated tube pushed into the soil so the farmer can see the water inside, even after it drops below the surface(IRRI, AWD fact sheet).
Our sensor sits inside that tube. It uses capacitive sensing with corrosion-resistant materials, giving a continuous reading in centimetres rather than a few fixed levels. A small solar panel and battery power it, and it sends the reading by radio (LoRaWAN) at regular intervals — no phone signal needed.
Our first design failed. That taught us what to build.
Version 1 — abandoned
Water closing a circuit between metal contacts told us “low”, “medium” or “high”. After a few days in muddy, salty paddy water, the contacts rusted and the readings became unreliable.
Version 2 — current design
The electrodes never touch the water electrically, so there is nothing to corrode, and the reading is continuous. This version has been tested in our family’s paddies in Kut Chum, Yasothon.
The founder documented both versions, with photos, on his blog:From rusty to reliable: AWD tube upgrade.
Aligned with IRRI’s safe-AWD protocol
NaLog uses IRRI’s published safe-AWD thresholds: irrigate when the water in the tube falls to about15 cm below the soil surface, and re-flood to about 5 cm(IRRI, AWD fact sheet). Around flowering the field is kept flooded; our rule here is slightly more conservative than IRRI’s window.
Sources
- IRRI Rice Knowledge Bank (Lampayan, Yadav, Humphreys). Saving Water with Alternate Wetting Drying (AWD). Fact sheet. www.knowledgebank.irri.org