When Hungary abandoned plans to build the Bős–Nagymaros dam system following mass opposition born of environmental protests, Czechoslovakia completed the project and diverted 85 per cent of the Danube’s flow. An international agreement governs how much water must be released into the Old Danube – but is this diversion really responsible for the river’s current record-low levels?
Conspiracy theories to this effect have been circulating, but it is unwise to believe everything that appears online, or everything loudly proclaimed by certain public figures.
Is Slovakia diverting the water to its own territory and leaving us thirsty?
The question has resurfaced as water levels on the Danube in Hungary have fallen to exceptionally low levels: is Slovakia really “taking” the river’s water, which is why there is so little of it in Budapest and Paks?
The short answer is that the Slovak hydroelectric system did indeed significantly alter the Danube’s natural flow. But the current record-low water levels are not the result of Slovakia withholding water. Every drop diverted to generate electricity is eventually returned to the river.
When the system linked to the Bős (Gabčíkovo) hydroelectric power station became operational in 1992, about 85 per cent of the Danube’s water was diverted into a canal built on the Slovak – formerly Czechoslovak – side. On Google Maps, the canal is conspicuously broad compared with the thin strip of the Old Danube, which forms the international border.
That does not mean, however, that 85 per cent of the water is “consumed”. Some of it returns to the Danube later, after passing through the power station’s turbines and via the navigation canal.
The International Court of Justice ruled that Czechoslovakia’s unilateral use of the river in this manner had deprived Hungary of its fair share of the jointly managed water resources. At the same time, it censured Hungary for abandoning its part of the project after the fall of communism, despite the existing intergovernmental agreement.
Why did the Slovaks build Bős?
Why was the system built in the first place? Hungary and Czechoslovakia signed a treaty on the Bős–Nagymaros dam system in 1977. Alongside electricity generation, its objectives included flood protection and improving navigation.
Hungary later halted the part of the investment for which it was responsible, while Czechoslovakia proceeded with the so-called Variant C on its own territory. It was able to do so because, unlike the Treaty of Trianon, the 1947 Paris Peace Treaty placed three additional villages on the right bank of the Danube under Bratislava’s jurisdiction.
That is where the Slovaks divert the Danube:
This meant that, along a short stretch, the river flowed exclusively through Slovak territory, allowing the authorities to do with it “whatever they wanted”.
In 1997, the International Court of Justice ruled that Czechoslovakia had been entitled to begin preparing Variant C, but that putting it into operation unilaterally had been unlawful. The court concluded that both countries had breached certain obligations.
The diversion also had serious environmental consequences in the Szigetköz region. Research has shown that it significantly altered the relationship between surface water and groundwater, lowered shallow groundwater levels in several areas and changed the natural fluctuations in the river’s flow.
The most significant fall in groundwater levels was recorded in the central Szigetköz.
Are the Slovaks really “stealing” the Danube’s water?
The present crisis, however, has become so severe for another reason. Prolonged drought and a heatwave have caused the Danube’s flow to fall dramatically. At the end of July, Budapest recorded a new all-time low water level, while at Paks the output of the nuclear power station had to be reduced because of the unusually low level of the river.
Under the 1995 Hungarian–Slovak agreement, an average of 400 cubic metres of water per second must be released into the Old Danube over the course of a year. During the growing season, the flow must stand at between 400 and 600 cubic metres per second, depending on hydrological conditions. Outside the growing season – in winter – it must be at least 250 cubic metres per second.
A further 43 cubic metres per second is released into the Moson-Danube and the seepage canal on the right bank. Slovakia is meeting these obligations.
The problem is that there is simply not enough water anywhere in the Danube basin. At Bős, only one of the power station’s eight turbines is currently operating, creating energy-related problems on the Slovak side similar to those facing Hungary at Paks.
The water diverted at Bős is returned to the Danube at Szap. This means that water levels in Budapest and Paks would be exactly where they are now even if the Bős power station did not exist. The only difference would be that there would be considerably more water in the Old Danube between Dunakiliti and Szap.
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In other words, Slovakia has not simply “turned off” the Danube before it reaches Hungary. The historic diversion did fundamentally alter the Szigetköz’s water system, but the present extraordinary low-water levels in Hungary are primarily the consequence of drought affecting the entire river basin.
8m water level difference on the Danube (September 2024 – August 2026):
Anita Orbán secures pledge from Slovakia
Foreign Minister Anita Orbán has had talks by phone with Tomas Taraba, Slovakia’s deputy PM and environment minister, who pledged to do everything to ensure that Hungary receives “the largest amount of Danube water possible”.
Orbán said on Facebook on Thursday that she had asked Slovakia to facilitate that Hungary receives the largest amount of water possible, and in an even distribution. She added that Taraba had made that promise despite the fact Slovakia is also suffering from drought.
“Hungary will receive the full amount of water due under international accords,” she said. “I wish to refute rumours suggesting that our neighbours could be blamed for low water levels on the Danube,” the minister said. She also thanked Taraba for making a commitment to transfer to Hungary a part of Slovakia’s water surplus if that country has rain earlier than Hungary.
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