: a cost-effective, open-source IoT system for water level monitoring in highly dynamic aquatic environments.

The deployment of low-cost network sensors (LCNS) for environmental monitoring has become increasingly prevalent in recent years, offering a cost-effective solution for enhancing spatial sensor coverage while minimizing financial constraints. This study presents , a water level monitoring system specifically designed for highly dynamic aquatic environments such as rivers, ponds or lakes. is an open-source, robust, and cost-effective Internet of Things (IoT)-based monitoring solution incorporating an ultrasonic sensor. The electronic components were carefully selected for their affordability, reliability, and performance. The system underwent a fully autonomous, long-term (3-year) field test in a challenging and highly dynamic environment - a sewer system - to validate its robustness. Its accuracy was assessed against a high-precision professional device, demonstrating an error margin of less than 1 cm. Additionally, was developed with a user-friendly design to facilitate accessibility for non-experts, aligning with the needs of citizen science initiatives and educational applications.