The most significant water investment in Budapest in recent decades completed

The comprehensive renovation of one of Hungary's oldest and most complex water engineering structures, the Kvassay Water Barrage, has been completed. The project was carried out by Colas Alterra Zrt. and STRABAG Generálépítő Kft. open book consortium, with the tasks divided between the National Water Authority (OVF) and the Middle Danube Valley Water Authority (KDVVIZIG).

Climate change impacts also urged investment

In the northern part of Csepel Island, the first navigation lock was opened in 1911, followed by the sluice gate, which supplied water to the tributary, and in 1962 a pumping station and hydroelectric power station were built on the Ráckeve-Soroksár branch of the Danube.
In recent years, the water challenges of climate change, obsolete technology and the low water level of the Danube have made it urgent to modernise and improve the facility.
The importance of the Kvassay's renewal is reflected in the presence of Csaba Lantos, Minister of Energy, S Zsolt V. Németh , State Secretary for Water Management, László Mészáros, Director of the Central Danube Valley Water Management Directorate, and István Láng, Director General of the National Water Directorate.

Why is he called the Lord of the Danube?

Because of its complex tasks, it is often called the Lord of the Danube.

• The Kvassay sluice is the first flood protection line for the Budapest-Baja flood protection basin.
• During periods of drought, the structure ensures controlled water levels in the Ráckeve-Soroksár branch of the Danube. When the water level of the Great Danube is too low and gravity does not allow enough water to flow into the tributary, the power plant also acts as a pump to feed the Soroksári-Duna. This branch supplies water to the fish ponds and irrigation systems of the Danube Valley.
• The structure also has a key role in regulating water quality. It would be an ecological disaster if there were not enough fresh water in the Danube tributary, as the water treated by the South Pest wastewater treatment plant flows into the river here. Without dilution, the nutrient content of the river water would be very high, causing significant damage to the biota.
• The Kvassay Sluice and its surroundings are a popular destination for water hikers and anglers.

The new pumping station must feed the tributary even at record low Danube levels

The decision to renovate the structures and build a new pumping station was taken in 2018. This year saw the lowest water level ever recorded in Budapest. The record of 51 centimetres, set in 1947, was overtaken by the aforementioned 33 centimetres in 2018.
During the period of water shortage, the water level in the Ráckeve-Soroksár branch of the Danube was 50 centimetres higher than in the Great Danube: this meant that the main branch could not gravitationally recharge the tributaries. The pumps installed could not transfer the water to the tributary when the water level was low.

A long-term and cost-effective solution, in addition to the renovation of the power plant's turbines, was the construction of a new pumping station capable of delivering at least 30 cubic metres per second of water from the main branch of the Danube to the Ráckeve branch of the Danube even at a water level 50 centimetres lower than the lowest water level measured so far - up to 17 cm measured by the Budapest water meter.

The athletics world championships and the Danube have also set the schedule for the works

On behalf of STRABAG, Gergely Kiss participated as deputy project manager, replacing Gergely Papp at the beginning of 2024, while on behalf of Colas Alterra, Dán Martin project manager was responsible for the overall renovation of the Kvassay complex, which was divided into two major phases. Wedged between these was the 2023 World Athletics Championships in Budapest, which took place in the vicinity of the worksite. Work was suspended during the competitions. During the construction of the project, three Danube tidal surges presented challenges for the experts.

The Colas and STRABAG have been refurbished by the experts:

• the turbines and related engineering of the power plant,
• the supply valve for the group of works,
• the crane tracks,
• upgraded the building's energy system,
• a new pumping station was built, with suction and discharge works and piping,
• renovation of the listed sluice building and the service dwelling near the complex, as well as the beam storage, and
• the sedimentation system was modernised.

A building event in the Danube branch

During the construction of the Kvassay lock and pumping station, the largest 150-metre long and 7-metre wide ice sluice in Hungary's history was built in the Danube riverbed. For the construction of the work area, a part of the riverbed was demarcated with reed plates, and for this phase, an 80-metre wide and 100-metre long floating barge was delivered to the tributary with two machines weighing a total of 130 tonnes on board.

8,000 cubic metres of silt and clay were removed from the demarcated and dewatered work area, and the fish were returned to the main branch.

Construction of seven-metre concrete walls in the river bed at a depth of 10 metres

Construction of the base slab and the beams in the clay was then started, at a depth of 10 metres below the level of the flood protection slit wall. At this stage, work was interrupted by another flood, this time in June 2024.

After desilting the area, seven-metre-high walls were erected in the riverbed and two pipes, each 1.8 metres in diameter, were laid to join into a single pipe to transport the water to the pumps.

The pipes are surface treated to meet the 100-year service life expected for water projects.

This phase of the project was affected by a new flood, the third in number. Despite the difficulties, by February 2025, only the finishing touches and the operational test were left. And today, the most important water project in the capital in decades was officially inaugurated.

Part of the Sandbanks could also benefit from water recharge

Around 400-450 thousand people live in the area covered by the project, and the number of people discovering the tourist and recreational opportunities of the Ráckeve-Soroksár-Danube branch is increasing.

Each year, 400-450 million cubic metres of water are discharged from the tributary into the Danube Valley water system, which is about a quarter of the total volume of Lake Balaton.