There has never been as much precipitation in Hungary as during the five days in September when the Danube was overflowing. The amount of precipitation has been measured since 1971, writes climate researcher Péter Szabó in his scientific analysis published in Másfelfok. This time Boris struck the continent, causing relatively little damage in Hungary compared to other countries. According to experts, this can be traced back to several reasons: after the great flood of 2013, the water department and state bodies were much more prepared for this year’s flooding, the meteorologists gave very accurate forecasts and the hydrological factors also developed well – among others, the level of groundwater, the speed of snow melting in the mountains – which we cannot influence, but they affect the level of flooding and the intensity of a cyclone. During a longer, dry period, the water level of the rivers and the surrounding soil drops, so that the heavy precipitation that occurs can be carried away without extreme flooding.
However, you can’t relax, because…
in the past seventy years, the frequency of cyclones affecting Hungary has not increased, but the amount of precipitation has doubled.
The experts preparing the analysis warn that if it is not possible to reduce the amount of harmful substances emitted, the frequency and intensity of floods will increase in the future.
As a result of climate change, the water flow of rivers changes through the water cycle. More moisture enters the warming air through evaporation, resulting in more precipitation, which increases the risk of floods. The other extreme – we have also seen examples of this – is that due to global warming, the water level of rivers drops significantly due to persistently high temperatures.
It can be particularly dangerous if a large amount of precipitation falls during the snow melt. This happened in the flood of March 2006, recorded as the largest flood in Hungary to date, and in the much smaller flood of December 2023, melting and precipitation were present at the same time, although the latter fell in the form of snow, which meant a smaller amount of water.
Although the amount of precipitation that fell during the five-day flood in September was not considered much, since this data has been officially measured, more rain fell six times during this period, the situation is quite different if we compare the period between May and September: in this comparison, Boris also thanks to this, 140 millimeters of rain fell this year. Only once before, in 1981, did this value exceed 100 millimeters. In addition, the 140 millimeters measured this year is an average value, in 45 percent of the Hungarian areas affected by Boris, the amount of precipitation reached 150 millimeters.
Three weather conditions simultaneously supported the formation of Cyclone Boris.
The major extremes – extreme heat and drought, followed by extremely large amounts of precipitation within a short period of time – are caused by activities that damage the environment and, as a result, global warming. If warming continues, we must prepare for even more extreme weather events. According to experts, in the near future the amount of precipitation will decrease further in the summer months and increase in autumn and winter. This means that the extremely dry period will last longer and the rainy months will be more intense than before.
These changes also affect the water level of the Danube, which can have a serious impact on our everyday life. The river fundamentally affects the operation of the Paks nuclear power plant, in addition to the water level, the temperature of the Danube also affects the operation. The agriculture and ecosystem of the catchment area also depend on water level fluctuations. Boat tourism must be suspended if the water level is too high or too low. The drinking water supply of cities and food safety can also be at risk if the river’s water level deviates from the average frequently and for a long time.
For all these reasons, in addition to adaptation, it is essential to significantly reduce the emission of greenhouse gases as soon as possible, to switch from the intensive use of fossil energy carriers to renewable energy, and to increase energy efficiency.
The water level of the Danube is also important for Europe
The Danube is the second longest and widest river in Europe after the Volga. The Száva, the Tisza and the Inn are the three largest rivers that transport water to the Danube. The river affects almost nine territories of Hungary, so it is not only in Hungary’s interest to keep the Danube’s water level in its bed. The domestic situation is determined by the Upper Danube watershed, the border of which is drawn by foreign experts at Bratislava, according to Hungarian experts, it extends to Gönyü. The latter also includes the Rá, which flows into the Danube near Győr. Moving towards the Black Sea, more and more tributaries flow into the Danube, as the volume of water increases, the speed of the river decreases.
Source: nepszava.hu
