(Paris) Floods in border regions of Russia and Kazakhstan are caused by an excess of snow which melted very quickly thanks to a rapid rise in temperatures, explains a climatologist, who places the influence of of climate change.
“Unlike northwest Europe, where flooding is primarily caused by winter precipitation that is projected to increase with climate change, the link between Russia’s 2024 floods and climate change is less clear,” explains Maria Shahgedanova, professor at the University of Reading, England.
“Spring floods in Russia and northern Kazakhstan, due to melting snow, occur regularly,” recalls the scientist, citing the serious episodes of “1922, 1942 and 1957”.
But “there is no clear trend of an increase in the frequency of floods” in these regions, where half are caused by melting snow and a third by excess rain, according to the climatologist.
“I would attribute the current event, first and foremost, to climate variability (as opposed to longer-term change),” says M.me Shahgedanova.
This year, “the thickness of the snow exceeded the norm by 30 to 60%”, then spring began by “going from negative temperatures to 17-18 degrees in a few days, causing very intense melting, and rains which followed worsened an already serious situation,” she explains.
Early melting
However, these “extraordinary” floods – which caused the Ural River to flood, flooding the Orenburg region in particular, and the Ishim River, which bathes the Siberian regions of Tyumen and Omsk and northern Kazakhstan – illustrate “perhaps the trend towards earlier and faster snowmelt and increased air temperatures in spring”, which remains to be observed over several years, she emphasizes.
On the one hand, the “rising temperatures throughout the year, but particularly in winter” in southern Russia and Kazakhstan is established by the IPCC – the climate specialists mandated by the UN – underlines the scientist. “Winter warming in the region is stronger than the global average, reaching 0.4°C per decade,” she adds.
On the other hand, going against the general trend towards a reduction in snow cover in the Northern Hemisphere, “the cumulative snowfall as well as the number of days with more than 20 cm of snow are increasing” in the Volga-Ural region and in Western Siberia,” where “the temperature remains negative in winter” despite global warming.”
“At the same time, we observe a clear trend of reduction in the duration of snow cover, both in observations and in projections,” adds the professor.
Beyond this possible tendency towards more rapid melting of a greater snow cover, the human factor counts, as illustrated by the controversy in Russia over the rupture of a dike in Orsk, a city of 220,000 inhabitants in the Urals.
“The main factor in the flood is nature, but problems with dike construction also matter,” said Mikhail Bolgov, a hydrologist at the Russian Academy of Sciences, interviewed by Russian media. Especially since if the dikes protect, “they can also raise the level because they narrow the river,” he added.
A reservoir, upstream, could have absorbed part of the floods, but it was already partly full, according to Dmitri Boldyrev, human rights defender quoted by Russian media.
“The employees were alarmed in January by asking the management to start the flow of water but the management did not want to because the previous year there had not been enough water,” he said. he accuses.
An investigation into negligence and violation of safety standards has been opened.
In Orenburg, another urban center on the Ural River, some residents also pointed out that large complexes had been built, in defiance of the rules, in flood zones.
reference: www.lapresse.ca