The principle
Why proxy signals carry pollutant information.
Pollutants change the physics and chemistry of water in measurable ways, and they travel with the flows that sensors already track.
- Conductivity rises with dissolved ions such as nitrate, and shifts when groundwater, runoff or effluent change the mix of water in the river.
- Turbidity tracks suspended particles, which carry particle-bound phosphorus and metals after rainfall and runoff.
- Dissolved oxygen and temperature reflect biological activity and nutrient enrichment through the day and the seasons.
- Ammonium, flow and rainfall signal effluent, agricultural runoff and dilution.
The evidence
What published research already shows.
At three river sites in the US national ecological monitoring network, models using only in-situ sensor variables (conductance, dissolved oxygen, temperature, turbidity and water level) explained 75–85% of the variation in nitrate, rising to 99% when time-series structure was included (Kermorvant et al., PLOS ONE, 2023).
Inferring bacterial indicators and organic load from low-cost sensors is already in commercial use in the UK. What has not been shown is inference of several pollutant classes from the same sensors, transfer to catchments with little laboratory data, and forecasts that follow pollution downstream. That is the focus of our R&D.
Validation
Every site is calibrated and scored before it goes live.
Each deployment is tested against laboratory reference samples. Clients receive a written calibration report with the metrics below before the site moves from supervised to live operation.
Target agreement between nitrate estimates and laboratory results at pilot sites
Target warning lead time for confirmed pollution events
Target false high-risk alerts per catchment
Target share of hourly forecasts produced despite sensor gaps
These are the acceptance targets for our pilot programme. Actual results for each site are reported to the client, including where a target is not met.
Research programme
The open questions we are working on.
Several pollutants from one set of sensors
Estimating nitrate, phosphate and dissolved metals together, using physically informed features rather than a separate model for each.
Transfer to data-poor catchments
Using catchment characteristics and targeted sampling so new sites reach useful accuracy within weeks, not years.
Catchment-to-coast forecasting
Combining hydrological routing with machine learning to forecast pollution arriving at towns, bathing waters and estuaries.
Robustness to real-world sensors
Detecting drift and fouling automatically and reporting uncertainty with every estimate.
References
- Kermorvant, C. et al. (2023). Understanding links between water-quality variables and nitrate concentration in freshwater streams using high frequency sensor data. PLOS ONE 18(6): e0287640. Link
- Environment Agency (2026). New data to drive action to improve England’s rivers and lakes (2025 classifications). Link
- Environment Act 2021, Part 5, sections 80–82. Link