CONSTANTA, Romania, Aug. 17 (Xinhua) -- Along the western shores of the Black Sea, vast stockpiles of coal and other commodities are piled up at the Port of Constanta, Romania.
However, persistently low water levels on the Danube are severely restricting upstream transport. Constrained by shallow stretches and reduced draft limits, barges are being forced to carry substantially smaller loads, leaving cargo stranded at the port.
Constanta is a major gateway between the Black Sea and Europe's inland waterway network and an important transit point for coal shipments bound for Serbia.
Roughly 900 kilometers upstream, Serbia's Nikola Tesla Thermal Power Plant (TENT) in Obrenovac, central Serbia, depends in part on coal transported along the Danube from Constanta. But receding water levels are making the supply route increasingly difficult to navigate.
TENT is Serbia's largest power-generation complex and produces roughly half of the country's electricity.
Driven by prolonged heatwaves and severe drought, Danube water levels have fallen to exceptionally low levels, disrupting inland waterway transport while putting additional pressure on energy generation and fuel supplies across the region.
Viorel Panait, general manager of Comvex, a major port operator in Constanta, said low water levels were limiting the number of barges able to navigate the river and the amount they could carry.
Serbian Mining and Energy Minister Dubravka Djedovic Handanovic told Radio Television of Serbia (RTS) that barges and tankers were operating at only 30 percent to 40 percent of normal capacity because of the low Danube levels.
Serbian Prime Minister Djuro Macut said on Aug. 2 that the country's energy situation was "serious and challenging," citing exceptionally low Danube levels and extreme heat among the factors putting pressure on the energy system.
But the effects of the hydrological crisis extend well beyond fuel transport.
As river flows diminish, hydropower generation is also being affected. The Djerdap hydroelectric complex on the Danube, jointly operated by Serbia and Romania, is Serbia's largest hydropower facility. Its Djerdap 1 plant has an installed capacity of 1,140 megawatts.
Dusan Zivkovic, chief executive of Serbia's state-owned power utility Elektroprivreda Srbije (EPS), said recently that Djerdap 1 was generating about 5,000 megawatt-hours of electricity per day, well below normal levels. The plant recorded its lowest monthly generation for May and June since it began operating in 1970.
The crisis is also affecting power plants that depend on the Danube for cooling.
Serbia's Kostolac thermal power complex, one of the country's major coal-fired power facilities, requires adequate Danube water levels to maintain the operation of its cooling systems. Djedovic Handanovic said the water deficit had temporarily reduced generation at some units by roughly one-third.
Further downstream, Romania's Cernavoda Nuclear Power Plant has been hit even more directly. Unit 1 was shut down in a controlled procedure on July 28 because of exceptionally low Danube water levels, while Unit 2 underwent a similar controlled shutdown on Aug. 13, leaving both reactors offline.
Official data show that, under normal conditions, the two reactors at Cernavoda together supply roughly 20 percent of the country's electricity.
Romania's nuclear operator, Nuclearelectrica, told Xinhua that Cernavoda uses an open-cycle cooling system that draws water directly from the Danube system. Exceptionally low water levels therefore impose operational constraints.
The company said nuclear safety remains the top priority and that, when water-related operating parameters approach their limits, plant operators may take necessary measures, including the controlled shutdown of one or both units, to maintain safety margins.
Further upstream, Hungary is facing similar challenges at the Paks Nuclear Power Plant, which has an installed capacity of about 2,000 megawatts and is a key source of the country's electricity.
The plant was operating at about 25 percent of capacity in mid-August after generation was curtailed as water levels fell, according to Hungarian authorities.
The Hungarian government has also taken emergency measures to mitigate the problem, including plans to construct an underwater sill near the plant to raise local water levels and help maintain adequate cooling conditions.
The impact is also being felt in regional electricity markets. Zeljko Markovic, an energy expert with the Energy Association of Serbia, told RTS on Monday that electricity prices on regional exchanges had reached around 173 U.S. dollars per megawatt-hour amid the drought and low Danube water levels, while evening prices had at times exceeded 811 dollars per megawatt-hour.
Markovic said the region was missing nearly 4 gigawatts of nuclear generation capacity as Romania shut down both reactors at Cernavoda and output at Hungary's Paks plant was sharply reduced. He said Serbia was not currently facing electricity shortages, but the loss of generation capacity across the region had contributed to higher prices.
For countries along the river, the drop in water levels is simultaneously affecting fuel transport, electricity generation and the cooling of power plants, adding to pressure on regional energy security.
Once a major artery for trade, power generation and industrial cooling, the Danube is now exposing the interconnected vulnerabilities of Central and Eastern Europe's energy infrastructure. ■