Ötz-T: 3D-printed open-source turbidity sensor with Arduino shield for suspended sediment monitoring.

Fine sediment production in catchments and transport through rivers to floodplains and coastal areas is extremely important for riverine, coastal and marine ecosystems, nutrient transport, global biogeochemical cycles, water quality and pollution. Due to the high cost of suspended sediment monitoring technology, it is extremely difficult to obtain a complete understanding of the physical connections between climate, hydrology, fluvial processes, and sediment fluxes, which requires measurements at many locations. For this reason, we have built an open-source turbidity sensor that brings accessibility to global river research. Compared to commercial turbidity sensors ( > 6000€), our low-cost version ( ∼ 200€) allows for multiple deployment and therefore a high spatial coverage of sediment fluxes. It is an optical scatter sensor with an 850 nm LED and two IR detectors, and features a temperature and pressure sensor. Our sensor is 3D-printed on a hobby printer and is programmed with Arduino IDE, making it accessible to those without high-tech workshop access and limited programming skills. It features a printed circuit board that stacks on top of an ultra low-power Arduino MKR WAN 1310, for durability and easy assembly. The sensor was tested during a flood in September 2022 on the Ötztal Ache in Tirol, Austria.

Open-source, low-cost, in-situ turbidity sensor for river network monitoring.

Fine sediment transport in rivers is important for catchment nutrient fluxes, global biogeochemical cycles, water quality and pollution in riverine, coastal and marine ecosystems. Monitoring of suspended sediment in rivers with current sensors is challenging and expensive and most monitoring setups are restricted to few single site measurements. To better understand the spatial heterogeneity of fine sediment sources and transport in river networks there is a need for new smart water turbidity sensing that is multi-site, accurate and affordable. In this work, we have created such a sensor, which detects scattered light from an LED source using two detectors in a control volume, and can be placed in a river. We compare several replicates of our sensor to different commercial turbidity probes in a mixing tank experiment using two sediment types over a wide range of typical concentrations observed in rivers. Our results show that we can achieve precise and reproducible turbidity measurements in the 0-4000 NTU or 0-16g/L range. Our sensor can also be used directly as a suspended sediment sensor and bypass an unnecessary calibration to Formazin. The developed turbidity sensor is much cheaper than existing options of comparable quality and is especially intended for distributed sensing across river networks.