The National Institute for Public Health and the Environment (RIVM) in the Netherlands is using OTT ecoN nitrate sensors and Hydrolab HL4 multiparameter sondes, connected to an OTT XLink 500 datalogger, to monitor the temporal variation of nutrients in ditch water. All measurement data is transmitted to the HydroMet Cloud platform for storage and analysis.
The goal of the WaterSNIP project is to improve the efficiency of water‑quality monitoring through the use of in‑situ sensors and to enable monitoring at a smaller spatial scale, transitioning from regional to local assessments.
Within the Minerals Policy Monitoring Programme (LMM), RIVM traditionally samples ditch water seven times per year. These samples are analysed in the laboratory across a wide range of parameters, with total nitrogen (Total‑N) and total phosphorus (Total‑P) being particularly important for compliance with Water Framework Directive (WFD) standards.
By measuring at a much higher frequency, RIVM aims to calculate more accurate average nutrient concentrations and improve understanding of nutrient leaching from farmland into ditches, as well as the chemical and biological processes driving these dynamics.
Real‑time measurement of Total‑N and Total‑P is generally only possible using expensive and power‑intensive analysers. Within this project, the OTT ecoN provides continuous measurements of nitrate (NO₃) as a key nutrient indicator.
The Hydrolab HL4 multiparameter sonde measures:
RIVM is investigating the relationship between these parameters and nutrient concentrations determined from laboratory analyses and ecoN measurements. The objective is to evaluate whether HL4 parameters can serve as proxy indicators for Total‑N and Total‑P.
Both the ecoN and HL4 record measurements at 15‑minute intervals.
Measurement data from the sensors is collected by the OTT XLink 500 datalogger and transmitted to the HydroMet Cloud web server for remote access and analysis.
The complete monitoring system is powered by a 20 Wp solar panel. The XLink 500 features an internal solar charge regulator, which charges the integrated 7 Ah battery, ensuring reliable long‑term operation in the field.