Remote monitoring of ponding water levels in rice paddies using an open-IoT device: SmartWT

Water management is a very time-consuming aspect of rice cultivation, especially when the AWD (Alternate Wetting and Drying) irrigation technique is adopted. This technique requires the water level in water tubes installed into the paddies to be monitored daily in order to determine the optimal time for submerging the field. This study proposes a remote monitoring system for the continuous monitoring of ponding water levels in flooded rice fields. Based on open-source architecture, the system uses an Arduino Nano in conjunction with a GSM board to acquire and transmit data for remote communication purposes. Data is measured by an ultrasonic distance measuring sensor installed on a tube inserted into the soil, perforated below the soil surface and lind above (i.e. named Water Tube). This enables the water level to be measured not only above the soil surface, but also below it to a depth of 30 cm. The entire system has been optimised for this operating environment and features a waterproof sensor and container. The device has been designed to operate using minimal power, facilitating installation in the field and minimising maintenance requirements. The device is designed to run on batteries alone, with a lifespan of approximately three months when transmitting every two hours. To extend this duration or to send data more frequently, either the batteries must be replaced, or a photovoltaic panel must be added. Several tests have been carried out in the laboratory and in the field to verify the sensor’s accuracy, assess issues associated with using an ultrasonic sensor inside a pipe in a field application, and investigate the influence of pipe diameter and environmental temperature. These tests have shown that accurate measurements require the use of an appropriately sized tube. Based on this research, the SmartWT was used to monitor the ponding water level and manage the AWD irrigation strategy in five fields belonging to three productive rice farms during the 2023 and 2024 agricultural seasons.