The largest flood in recent years could reach its peak in Budapest on Saturday. However, an expert from the HUN-REN Centre for Ecological Research assures that the drinking water production wells along the Danube, and consequently the drinking water supply, are safe. According to the ecologist, while addressing the flood situation is naturally the immediate priority, long-term water retention must also be considered.
Experts expect the Danube to crest in Budapest on Saturday. Although the river is not forecast to reach the 2013 record level of 891 cm, it is expected to peak at around 850 cm. As the flood approaches, the question arises: is the capital’s drinking water supply safe? The short answer is yes.
This spring saw the completion of the five-year 'Clean Drinking Water' research project, carried out under the Hungarian National Excellence Programme, with the HUN-REN Centre for Ecological Research (HUN-REN CER) as one of its consortium members. Project leader Attila Engloner explained that they also investigated whether Budapest’s drinking water remains safe during floods. Their findings showed that the Danube’s bank filtration system is so effective that there is no immediate threat to the city’s drinking water supply. However, large floods and extremely low water levels continue to pose ongoing challenges.
Budapest is supplied with drinking water from over 700 production wells located along the Danube, distributed across various areas. This distribution ensures that most wells can continue to provide drinking water even during a flood. The safety of the supply is further supported by the extensive experience gained from previous floods, particularly the record levels of 2013.
During floods, however, the water quality of the Danube can change significantly. Despite the increased dilution effect, not all pollutants are reduced. The water may also carry contaminants from flooded areas (such as riverbanks or roads) that are not typically affected at lower water levels.
Fortunately, the living coating on the gravel bed of the riverbed, known as the biofilm layer, significantly purifies the Danube’s water as it percolates through to the underground layers from which drinking water is drawn. “Our research results show that this purification effect remains effective even during the extreme hydrological events we have experienced so far,” adds the researcher.
According to Attila Engloner, more and more people are realising that climate change is not a future process but something we are experiencing now. He stressed that while the rise in temperature is clear, future changes in precipitation vary across climate scenarios. In our region, projections are uncertain: annual precipitation could either decrease or increase. “However, it is not only the amount of precipitation that matters, but also its distribution,” adds the senior researcher at HUN-REN CER.
The distribution of precipitation is expected to become increasingly extreme, potentially leading to major floods similar to the current one. We need to prepare for these sudden floods as well as for the longer periods of low water and drought between floods, which also pose water management and environmental challenges.
When a large volume of water arrives, as is the case now, the primary task is, of course, flood management. However, according to the researcher, increased attention must also be given to water retention. “Two very important, concurrent tasks are managing the flood and ensuring continuous, long-term retention of water, which is essential for drinking water supply, agriculture, and the preservation of natural ecosystems,” the ecologist emphasised. He added that in Hungary, too, there are already proposals and solutions for directing and retaining seasonal excess water in the appropriate areas.