Sensors for high-frequency water sampling
What sets running water apart is that it’s constantly moving and changing. All the time. So when we want to understand what’s happening in a stream or river, occasional samples aren’t enough. We need sensors that help us track what’s going on in the water.
Environmental monitoring of running waters is challenged by their dynamic nature. Monthly sampling intervals provide only episodic snapshots, which may miss short-term fluctuations caused by weather events, hydrological variability, or anthropogenic influences. To address this limitation, researchers at the Swedish University of Agricultural Sciences (SLU) employ in-situ sensors capable of continuous, high-frequency measurements, significantly narrowing the data gaps from weeks to minutes.
These sensors enable the detection of rapid chemical changes, such as shifts in pH, turbidity, or oxygen concentration, which are often driven by snowmelt, precipitation, erosion, or nutrient pulses from surrounding landscapes. Such insights are vital for understanding when and why critical thresholds are crossed, e.g. oxygen depletion that threatens aquatic fauna, or acidity drops detrimental to biodiversity.
Sensor deployed across Sweden provide valuable data on water quality dynamics in agricultural, urban, and forested catchments. Five of the sensor stations are supported by the Swedish Agency for Marine and Water Management (HaV) as part of a national environmental monitoring development initiative, while two others are funded by the EU LIFE IP Rich Waters project.
One notable case is the sensor installed at the outlet of the Fyris River at Flottsund. This location is ideal for tracking cumulative effects of land use, urban runoff, and wastewater discharge. Since the Fyris River flows into Lake Mälaren - a drinking water source for approximately two million people and a key ecosystem - the real-time monitoring of parameters like conductivity, turbidity, and nitrate offers critical data for safeguarding ecosystem services and informing water management strategies.
The sensors, housed within protective tubes submerged below the surface, operate year-round, allowing researchers to capture key seasonal events such as spring flood dynamics and associated nutrient transport. Sensor data are published in annual reports and contribute to the broader understanding of water quality trends and their driving factors.
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