In response to the environmental disaster on Croatia’s Zrmanja River caused by leaks of hazardous materials from an abandoned aluminum oxide factory, Geolux has installed advanced HydroStations with integrated sensors, oil spill detectors, and remote monitoring capabilities to enhance early warning systems and protect the region’s fragile ecosystem.
The Disaster
In December 2019, poor waste management at an abandoned thermally grown oxide factory in Obrovac led to a major environmental incident. Heavy rainfall washed waste from two open-air pools into the Zrmanja River, releasing highly alkaline red sludge. This by-product of alumina production contained hazardous sodium and potassium hydroxides along with heavy metals in concentrations far above normal soil levels.
At closure, the site still held 750,000 m³ of red sludge and 1,000,000 m³ of lye waste, posing an ongoing threat to the surrounding karst environment. Following the leak, authorities classified the site as requiring urgent rehabilitation.
A Fragile Environment
The Zrmanja River is famous for its crystal-clear waters, canyons and waterfalls, flowing 69 km through karst terrain into the Adriatic. Its basin connects with underground networks and tributaries, making it particularly vulnerable to pollution.
Leaching of toxic sludge, oils and even radioactive materials into the river is frequent during heavy rains. Fuel oil leaks have also contaminated the river and the Novigrad Sea, sometimes covering the surface with oil slicks that endanger navigation and ecosystems.
HydroStations to the Rescue
To counter these risks, Geolux deployed HydroStations at key sites:
- Zrmanja River near Obrovac
- Knin, at the source of the Krka River
- A bridge at the entrance to Krka National Park
These stations integrate water level and flow sensors, oil-on-water detectors, and inspection cameras. The oil spill detectors provide early warnings, allowing rapid response before pollution spreads.
Each HydroStation is self-sustaining with a solar panel, datalogger, MPPT charger, and backup battery. IP68 enclosures protect equipment from dust and harsh conditions, while modular design supports third-party sensor integration.
Advanced Monitoring Capabilities
Stations at Knin and Krka include additional sensors:
- Contactless water temperature sensors
- Multi-depth sensors for monitoring river–sea mixing in the Šibenik Channel
All locations are equipped with HydroCam site cameras for remote visual inspection. Features include infrared reflectors for night mode, day/night filters, remotely adjustable zoom, and reliable operation from –20°C to +60°C.
Conclusion
By combining radar hydrology instruments, oil spill detection, and remote monitoring, Geolux HydroStations provide a powerful tool to protect the Zrmanja River and its ecosystems. These stations enhance early warning, improve disaster response, and ensure long-term resilience against industrial pollution in one of Croatia’s most unique natural landscapes.