Author(s): Benjamin Freudenberg; Andre Niemann

Linked Author(s): Benjamin Freudenberg

Keywords: Low-cost sensor nodes; LoRaWAN; Monitoring of surface waters; High-resolution data; Wireless sensor networks

Abstract: One component of modern urban design - including in the context of smart cities - is management of surface waters. Blue-green infrastructures are intended to help adapt to climate impacts (urban climate, extreme precipitation events, droughts). However, in the context of integrated planning in water management, uniting ecological and economic aspects often poses problems for local actors in decision-making. This includes the definition of measures and the development of long-term strategies. Small-scale information could be used to improve the understanding of water bodies, their dynamics, and their interaction with the environment. In order to be able to capture these relationships, high-resolution data is needed. One enabler of new knowledge generation can be IoT-supported system-state monitoring based on multiple data sources. This can be implemented using low-cost battery-powered sensors and integration in LoRaWAN. These represent an autarchic system without the need for external infrastructures. For example, no external power supply or existing cable network is required on-site for data transmission. Initial experience has shown that such sensor nodes, no larger nor heavier than a lunchbox, can be deployed easily and flexibly. Each transmission is made with small (few bytes), end-to-end encrypted data on broadband frequencies and can thus bridge large distances of up to several kilometers. Depending on the use case, battery capacity and transmission frequency the sensors can be operated maintenance-free for more than a year. Accordingly, these technologies are attractive for use in operations. The low procurement costs of the technology also allow cost-effective replacement when needed. All in all, this enables a new form of environmental monitoring by setting up an adaptable and high-resolution measurement network for monitoring water bodies. In a pilot phase, several ultrasonic sensors were installed at selected catchments in Germany. All data is transmitted via LoRaWAN to The Things Network (TTN). TTN’s application server exposes an MQTT server that allows logging the data to an Influx database using the open-source server agent Telegraf. All data is then tested regarding their reliability and data quality based on reference measuring points provided by a local waterboard. Furthermore, different frequencies and sample sizes are used to draw conclusions concerning optimal operation of the sensors for the mapping of events. Low-cost sensors are not an equivalent replacement for existing high-precision measurements. Their role and the possible applications of a secondary environmental monitoring layer in the management of surface waters thus still needs to be assessed. This study reflects on pathways and limitations of a high-spatial-resolution environmental monitoring layer. This is done considering decision making processes and the existing, traditional environmental monitoring of surface waters.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221412

Year: 2022