Last weekend, one of the worst storms on record severely disrupted everyday life in Slovenia, affecting numerous families, public institutions and the economy. Rectifying the consequences of that natural disaster will require massive efforts for the foreseeable future in large parts of the country.

The GEN Group, which performs activities that are fundamental for the functioning of the country through the production and supply of electricity, has been confronted with extreme conditions on the Sava River. After hydropower plants, with the exception of two on the upper course of the river, were gradually shut down on Friday, all power plants have been back in operation since Monday. The Krško Nuclear Power Plant (NEK) has been functioning stably and at full power at all times.

Impact of the flood wave limited through the appropriate preparation of reservoirs

In anticipation of the flood wave, teams of hydroelectric power plant operators on the Sava River implemented the prescribed measures to prepare reservoirs for the safe passage of the flood wave and the synchronous passage of water. Water volumes were extreme. To illustrate: from 4 to 7 August, close to 700 million m³ of water flowed down the lower course of the Sava River, representing one tenth of the average annual flow.

Additional problems were caused by the huge amount of flood debris, sludge and other contaminants. For this reason, the NEK’s cooling towers were operating at full capacity already on Friday morning. For the first time since its construction, the flood relief valve at the Brežice HPP was activated on Friday afternoon, which helped to slow the flood surge towards Brežice by filling retention basins in the Vrbina area.

The appropriate containment of the flood wave facilitated the successful evacuation of people from the camp in Šobec, and helped maintain more stable conditions in Medvode, where the Sora River exceeded all previously recorded inflows. Through the timely lowering of the water level at the Vrhovo HPP reservoir and the requisite flood protection, the situation in Radeče was stable and flooding did not occur. Flood waters in the municipalities of Sevnica and Krško did not cause any major damage thanks to flood protection put in place during the construction of hydroelectric power plants on the lower course of the Sava River. The situation was different in the Municipality of Brežice, where flood-prone areas are still partially or completely unprotected due to delays in the construction of the Mokrice HPP.

Requirements regarding flood protection are crucial in the construction of hydroelectric power plants

The flow rate of the Sava River was around 10% higher than in 1990, which is remembered for severe floods in the municipalities of Sevnica and Krško. The functioning of the chain of hydroelectric power plants and flood protection measures proved to be effective. It is evident from this most recent experience that construction of the Mokrice HPP is crucial for flood protection in areas below the Brežice HPP.

The chain formation of reservoirs, as well as their shape and size, facilitate the management of flood waters and regulate groundwater levels. In addition, the multiplicative effects of energy facilities ensure long-term financial and human resources for the prudent maintenance of embankments and other protective systems, which in turn contributes significantly to the effective operation of energy facilities in crucial moments.

More information about the management of flood waters along the chain of hydroelectric power plants is provided by the subsidiary HESS.

Safe and reliable production and supply of electricity at all times

The energy mix of the GEN Group, which is based on resilient and weather-independent nuclear power, facilitated an appropriate and effective response in challenging conditions. The NEK operated safely and stably at full reactor power throughout the emergency, and once again demonstrated its reliability, virtually independent of weather conditions.

In accordance with its role in the Slovenian electric power grid, the Brestanica Thermal Power Plant (TEB) responded to the immediate need for its connection to the grid. In anticipation of increased flow rates, preliminary equipment tests were performed and reserve power was successfully provided to the electric power grid on Saturday evening in the scope of so-called ancillary services (manual frequency restoration reserve). The TEB also produced a portion of lacking quantities of electricity of the GEN Group, while remaining quantities were ensured at the Group level through immediate purchases on the market.

The GEN Group will strive to the best of its ability to ensure a long-term stable and secure future for all, primarily through the excellence of its operations in the energy sector. Our sincerest sympathies to all of those who have been affected in any way by this natural disaster.