Was the water purposely withheld before the destruction of the Kakhovka dam? Caution

Who destroyed the Kakhovka dam, located downstream of the Zaporizhie nuclear power plant in Ukraine? On social networks, a graph showing a rise of more than 3.5 m in the reservoir is interpreted to support opposing hypotheses, without this constituting concrete and sufficient proof.

On Twitter, Megaupload founder Kim Dotcom estimated on June 6, in a post shared more than 7,500 times, that “data suggests that Ukraine artificially raised the water level in the reservoir to the highest level in eight years just before the dam was destroyed. Evidence of guilt? “.

He then asks: Ukraine controlled the other dams upstream of the Dnieper, he argues, and by “raising the water level to its record, the Zelensky regime wanted to cause maximum flooding after the destruction of the dam? Except that the Dnieper is on the front line, Russian forces control the left bank of the river, which includes the dam and the Kakhovka hydroelectric plant, as shown in a diagram from the American Institute for War Studies (ISW). The same graphic was later released to assert, conversely, that it was the Russians who held back the water before planning the destruction of the dam.

A worrying drop in February

This graph is very real and comes from Theia, a French data center, which from satellites observes the continental surfaces, including the water levels via Hydro web site. According to these data, the level of Lake Kakhovka was 14.03 m on February 2, 2023, the lowest since 1992 if compared to US Department of Agriculture data.

This drop in level, worrying if it continued, could also have consequences on the cooling of the nuclear power plant of Zaporijie, located approximately 140 km upstream. A minimum of 12.7 meters according to the International Atomic Energy Agency (IAEA), is necessary so that water can be pumped into the tank to cool the six reactors on shutdown. We will come back to it.

There followed, from February, a spectacular rise in the level, with a peak on May 21 at 17.54 m. Data is no longer provided on Hydroweb since June 4th. The National Center for Space Studies, partner of the pole, did not wish to comment on this elevation.

“The Ukrainian authorities do not have access to the dam”

Contacted, Iuliia Danylenko, head of laboratory at the Ukrainian Institute of Hydraulic Problems and Spatial Planning, explains to us that the management of the 6 dams on the river is regulated by an official document, the rules of operation of the Dnieper reservoirs . These rules take into account the needs of the stakeholders (for hydroelectricity, fishing, industry, irrigation, etc.) and take into account the weather conditions of the year (dry, normal, wet) to regulate the levels in the tanks.

This winter and spring, “the season has been very wet, there has been a lot of rain upstream, which means that the reservoirs are supposed to be full, she explains. To prevent overflow, all dams must release water downstream to the Black Sea. But unlike the 5 other dams on the Dnieper still in Ukrainian hands, that of Kakhovka has been “under total Russian control since February 24, 2022, she continues. The Ukrainian authorities do not have access to it and have not been able to open or close the valves. The water level can rise if those operating the dam do not follow the rules and do not open the necessary number of gates at the right times. Occupation forces are supposed to ensure the normal functioning of the dam. She wonders: “Why were the floodgates not opened?” Was there a purpose to this? »

An insufficient “discharge rate”

Mid-May, the New York Times also questioned this rise in the lake, which then reached, according to an analysis of satellite images, worrying levels where the water seemed to overflow from the top of the dam. “The reason for this significant rise is unclear,” the reporters wrote. David Helms, a former US Air Force meteorologist who researched the dam, said Russian forces appeared to have opened too few floodgates to control the flow brought in by melting snow and spring rains. “The river pours out a lot of water [dans le réservoir] and this far exceeds the rate of discharge, ”he said daily.

Since June 6, Moscow and kyiv have been rejecting responsibility for the destruction of the Kakhovka dam, which heralds a humanitarian and ecological disaster. Implicated on Tuesday by Ukraine, which accused it of having dynamited the dam to cut the road to an offensive in the south towards Crimea, Russia asserts on the contrary that it is of a “barbaric” act committed by the Ukrainians.

Continue to cool the Zaporizhie nuclear power plant

The destruction of the dam also has consequences for the cooling of the Zaporijie nuclear power plant, under Russian control. The level of the reservoir has been falling continuously since June 6 and reached the critical threshold of 12.7 m on June 8 at 6 a.m. In a press release, the IAEA stressed, however, that pumping operations should “be able to continue even if the level fell below” and now sets the limit at “11 meters or even lower”. The retention pond, smaller reserves and on-site wells “can provide cooling water for several months,” the IAEA said.

Location of the Zaporizhie nuclear power plant in relation to the Kakhovka dam and hydroelectric power station.
Location of the Zaporizhie nuclear power plant in relation to the Kakhovka dam and hydroelectric power station. – IRSN

The French Institute for Radiation Protection and Nuclear Safety (IRSN), which follows the evolution of the level of Lake Kakhovka, is not able to provide explanations for the rise observed between February and May. “The concern today for the plant is linked to the holding of the dam”, points out Karine Herviou, deputy director general, in charge of the nuclear safety pole at the Institute. With the drop in the level of the Dnieper, “the risk is the loss of watertightness of the basin [de rétention] even the erasure of the dike which surrounds it because of the pressure exerted by the water contained in the basin, she underlines. The dike was not sized to hold if there is no water on the other side. »

As part of the post-Fukushima stress tests, the Ukrainian operator estimated that the holding of the dike is guaranteed for a level of 10 m to the right of the plant, underlines a note from IRSN, who will follow “carefully the situation in the coming days”. If ever this dam disappears, pump trucks could make it possible to ensure the necessary supplement in the basins fountains from the water remaining in the Dnieper, adds the IRSN.

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