A low-cost multi-sensor platform for monitoring real-time hydrological and biogeochemical dynamics across land-stream interfaces

The recognition of global change impacts on catchments and the waters they drain emphasizes the need to better understand and predict both hydrological and biogeochemical dynamics at the terrestrial-aquatic interface. To achieve this great endeavor, a key priority is to substantially increase the number of multi-annual time series, covering a broad range of river types and filling existing geographical gaps (e.g., low-income regions in/and remote areas). However, commercial multi-sensor solutions are not affordable to everyone. The multi-sensor platform consists of a STM32 micro-controller board combined with a data logger module, and a set of sensors to measure hydro-chemical properties both at different depths in soils (adjacent to the streams) as well as within streams: temperature, water level, moisture, electrical conductivity, turbidity, dissolved O₂ and CO₂. The monitoring system is also equipped with a wireless communication capability using LoRa network technologies. To make our project as accessible as possible, we have designed, built, and programmed the multi-sensor adopting the Open Source Hardware and Software philosophy. Through the complete processes of pre-calibration and in situ measurement, the preliminary results illustrate that the proposed multi-sensor system can provide long-term, high-frequency hydrological and biogeochemical data across land-stream interfaces while keeping the balance of costs and accuracy.