Successful passage of a high wave through the Arda cascade
A high wave was recorded passing through the three reservoirs of the Arda cascade operated by NEK EAD – Kardzhali, Studen Kladenets and Ivaylovgrad - as a result of heavy rainfall over the past 24 hours under a red alert in southern Bulgaria on 5 February 2026. As of 6 February 2026, we report the successful passing of the high wave, thanks to the continuous operational control carried out by the company's experts.
During the passing high wave, the peak inflow to the first stage of the cascade – the Kardzhali Reservoir – was recorded at 863 m3/sec. In the evening hours of 5 February 2026, two of the four overflow valves of the dam were opened in order to release water flows and reduce its storage volume. With the Kardzhali HPP operating 24 hours a day, the maximum recorded water flow rate through the spillway is 450 m3/sec.
The peak of the total inflow to the Studen Kladenets Reservoir was recorded at 1,870 m3/sec. In the late hours of 5 February 2026, five of the dam's nine overflow valves were opened. With the Studen Kladenets HPP operating 24 hours a day, the maximum overflow water flow rate through the spillway is 1,320 m3/sec.
The peak of the total inflow to the Ivaylovgrad Reservoir, the last stage of the cascade, was recorded at 1,750 m3/sec. The reservoir began to overflow at 23:00 on 5 February 2026, and by 12:00 on 6 February 2026, the overflow water flow rate was 538 m3/sec.
NEK EAD continues to exercise constant operational control over the situation and remains ready to take timely action.
