Information as of 9 January 2026, on the condition of the dams and facilities managed by NEK EAD in the Arda cascade.
At 12:00 p.m. on 9 January 2026, the inflow to the Arda cascade had already decreased tenfold and amounted to 131 cubic meters per second. A water volume of 94 cubic meters per second passes through the spillway. The total volume of the high wave passing through the reservoir was 100 million cubic meters, which is more than the total usable volume of the reservoir, i.e., it is not possible to regulate the incoming water quantities without overflowing. During the high wave period, Ivailovgrad HPP operates around the clock.
Arda Cascade consists of Kardzhali, Studen Kladenets, and Ivailovgrad reservoirs. As of 9 January 2025, the cascade is operational under subsiding complex meteorological conditions, with high storage volumes and a passing high wave through the Ivailovgrad reservoir.
Arda River is characterized by significant fluctuations in discharge and high winter flows, requiring increased attention to dam management in view of the frequent passage of high waves through the cascade and the associated safe overflow through the spillways.
The volumes stored in the reservoirs are as follows:
- Kardzhali Reservoir – 87% of its total volume
- Studen Kladenets Reservoir – 94% of its total volume
- Ivailovgrad Reservoir – full capacity with water overflowing through the spillway.
On 7 January 2025, a sharp increase in the inflow to the Ivailovgrad reservoir was observed as a result of intense torrential rains in the Krumovitsa River basin. After analyzing the data, a procedure was initiated to transfer the dam under high wave conditions. The necessary steps were taken in a timely manner to notify all institutions, agencies, and local authorities involved in the disclosure process. At 22:00 that same evening, a peak high wave of 1,156 cubic meters per second was recorded. With this volume of water, the reservoir quickly fills to capacity and at midnight begins to overflow through its relief facilities. The operational staff on duty at NEK EAD begins reporting information on the condition of the dam every two hours, around the clock.
In conclusion, Ivailovgrad dam fulfilled its purpose and played an important role in controlling the torrential nature of the Arda River, reducing the peak of a high wave of 1,100 cubic meters per second by about 70% to 330 cubic meters per second released downstream of the dam.
National Electricity Company (Natsionalna Elektricheska Kompania) approaches the water management of its multipurpose and significant dams with a high level of responsibility.
