SmartWT: an IoT device for the remote monitoring of water levels in rice paddies

This study proposes a remote monitoring system for the ponding water level in flooded rice fields. The system is based on a completely open-source architecture, with the data acquisition and transmission operations realised using an Arduino Nano in conjunction with a GSM board. The data is measured by an ultrasonic distance measuring sensor installed on a tube inserted into the soil, perforated below the soil surface and continuous above (i.e. Water Tube). The entire system has been optimised for the environment in which it operates, with a waterproof sensor and container, and the device has been designed to require low power to operate, making it easy the installation in the field and minimising maintenance requirements. The device is designed to run on batteries alone, with a life of approximately 3 months when transmitting every 2 hours. For longer transmissions, the batteries must be replaced, or a photovoltaic panel can be connected. Several tests have been carried out in the laboratory and in the field to verify the actual accuracy of the sensor used, to assess any problems in using an ultrasonic sensor inside a pipe in a field application, and to study the influence of pipe diameter and environmental temperature. These tests have shown that precautions are needed to obtain accurate measurements. Based on this research, the SmartWT was used in the 2023 and 2024 agricultural seasons to monitor the ponding water level in five fields of three productive rice farms and, based on these measurements, to manage the AWD (Alternate Wetting and Drying) irrigation technique in the fields.