June 6, 2023

expert reaction to reported attack on Ukraine’s Kakhovka dam

It has been reported that the Nova Kakhovka dam in the Russian-controlled area of southern Ukraine has collapsed.

Prof Dragan Savic FREng, CEO of KWR Water in the Netherlands, and Professor of Hydroinformatics, University of Exeter, said:

“The Kakhovka Reservoir is part of the large Dnieper River complex used for electricity generation, irrigation and domestic water supply. The shallow but large reservoir (average depth is about 8 metres and the total volume is 18,200 million cubic meters) receives the water from the upstream 5 reservoirs on the River. Partial destruction of the dam, which combines earthfill dams (on the right and left banks) and concrete parts (in the middle) has already caused a significant impact due to downstream flooding. However, long-term consequences are difficult to assess at the moment but based on the experience of the removal of dams in the USA, it could include excessive erosion of the reservoir and downstream areas and pollution due to the release of toxic and contaminated sediment, which has accumulated over the years at the bottom of the reservoir.”

Dr Eldad Avital, Reader in Fluids and Acoustics at QMUL, said:

“That dam was already damaged due to previous war actions. The sluice gates were not working properly, so the reservoir water already went over the top of the dam instead through the spillways as intended and thus weakening the dam (the dam was built in the early 50’s). The pictures indicate a point failure that later grew to a significant collapse of the dam. If this was done by an explosion, it was probably done internally as it is much easier to damage the structure from the inside than from the outside (see the old Hollywood film Force 10 from Navarone, which actually had some good engineering points when it came to dams).  In terms of environmental effects, judging from previous incidents of flooding, we can regretfully expect landslides, loss of life, transport ways being destroyed, destruction of properties and emergence of diseases.”

Dr Elisabeth Bowman, civil and structural engineer at the University of Sheffield, said:

“The dam, part of the Kakhovka hydroelectric power plant, is 30 metres tall, 3.2 km long and is a run-of-the-river barrage dam – this means the gates can be opened in sections to release water as needed. Construction was started in 1950 and finished in 1956. It holds around 18 cubic km of water.

“From what I can understand, the dam is partly an embankment dam made of compacted soil and rock at the sides with a reinforced concrete structure in the centre section which forms the main hydroelectric works. The operational head of water was around 16m behind the dam – it dropped to 14m in February 2023 due to deliberate opening of the sluices back in November 2022, but was back around 16m when the breach occurred.

“It appears that the breach is limited to the structural section rather than the soil which is very fortunate. Once a breach begins in a soil embankment it can downcut very rapidly through scour, widening the breach, such as what happened with the Teton dam failure in 1976 or the more recent 2020 Edenville dam failure in the USA – this was a small head but the process would be similar. So long as the structural elements, such as sluice gates and spillways, remain intact however, the flow out should lessen over time.”

Prof Chris Binnie FREng, Visiting Professor at University of Exeter and Chair of Tidal Engineering and Environmental Services, said:

“The images I have seen show two breaches, either side of a structure.  Were the breach to be caused by excess upstream water level there would only be one.  Thus natural causes are highly unlikely.

“Shelling by Ukraine is highly unlikely as it would need to get massive explosives close to the foundations.

“The river will drop to just above the lowered foundations, thus lowering water level permanently. Pumping for water supply to the Crimea could restart fairly soon.”

Prof Roger Falconer, CH2M HILL Professor of Water Management, Cardiff University, said:

“When a dam fails (almost instantly) then this is a very extreme event and the short-term impacts are extremely challenging, with longer terms impacts also being considerable in many cases.

“Put into context, the modelling of flooding due to extreme storm events can now be modelled accurately using a number of widely used computational hydrodynamic models. However, modelling dam break flows, and the sudden wave effects, requires much more complex models as the water wave propagating downstream is supercritical and similar in context to supersonic flight etc., i.e., the wave is travelling faster than the natural speed of a wave disturbance in water. Such models are only available from specialist consulting companies specialising in modelling extreme events.

“The downstream wave raises the water level rapidly as the large volume of water stored in the reservoir is rapidly propagated downstream. The water level rises much faster than an extreme flood event and the warning time is extremely short. Such a dam break failure can often lead to many deaths downstream.

“As the reservoir empties the water level in the reservoir drops dramatically and the upstream level also drops as a result of what’s termed backwater effects. The resulting drop in the river water level can have an impact many tens or even hundreds of miles upstream of the head of the reservoir, depending on the upstream river bed topography or bathymetry.

“This upstream drop in water levels could impact the flow of water into water supply inlet pipes or canals, having a severe impact on water supply for communities and for agriculture – particularly crop production.

“The upstream reduction in water levels will also invariably affect ground water levels, particularly close to the river, which can in turn affect the characteristics of wetlands, habitats etc.

“When a dam has been in place for typically 70 years (as for Kakhovka dam) then the river bed morphology downstream of the dam and within and upstream of the reservoir will have stabilised. When the dam fails suddenly as for the case of the Kakhovka dam, then it will take some considerable time for the morphology to stabilise again and for the bed sediments etc. to operate as a stabilised system.

“With the future shallower depths in the river system, where the reservoir was previous and the previously raised backwater levels, this reach will now have higher velocities for the same river basin flows and will have less transit time for pollutants etc. to decay biologically. Therefore the potential risks of future pollution levels could be increased downstream.”

Dr Modupe Jimoh, Assistant Professor of Civil and Humanitarian Engineering at the University of Warwick, said:

“The bombing of the Ukrainian Dam has inflicted severe damage not only on the physical infrastructure but also on the vital hydroelectricity power plant it supports. This act has far-reaching consequences for Ukraine, the broader region, and the global landscape. Hydroelectric power plants play a crucial role in providing sustainable and clean energy. They are also designed for water supply and irrigation purposes. The destruction of the Kakhovka hydroelectric power plant dam not only disrupts the generation of electricity, destabilizing the entire power grid; it also leads to flooding of the local area and loss of lives, livelihoods, properties and farmlands.

“The impact on the hydroelectric power plant will also extend to the socio-economic fabric of the region. The disruption in electricity supply will have severe implications for industries, businesses, and households that rely on a stable and affordable power supply. Without electricity, critical infrastructure such as hospitals, schools, and water treatment facilities will be severely affected, further exacerbating the humanitarian crisis in the region.

“The destruction of the dam’s water supply infrastructure would lead to a lack of water and significant shortages in certain areas, putting people at risk of health and sanitation issues. This setback would also hinder progress toward achieving SDG 6 Goal, which aims to ensure access to water and sanitation for everyone. Additionally, the war in Ukraine has already had a significant impact on global food availability and prices. The destruction of the dam and farmlands downstream would only worsen the situation, leading to even less food available locally and globally.

“Furthermore, the bombing of the dam has raised environmental concerns. Hydroelectric power is known to be a renewable and eco-friendly energy source because it doesn’t produce greenhouse gas emissions while in operation. However, destroying the dam could result in industrial chemicals being released into the water and environment, as well as habitat destruction and ecological imbalances. These ecological effects could have long-term impacts on the nearby ecosystems, wildlife, and biodiversity.

“This incident serves as a stark reminder of the vulnerability of critical water and energy infrastructure in times of conflict. It emphasizes the need for greater international cooperation to protect such essential facilities. Targeting these installations undermines a nation’s energy security and has far-reaching implications for global stability, food prices, energy markets, and sustainable development goals. It is imperative that we work together to prevent and respond to such attacks, ensuring the security and resilience of critical infrastructures worldwide.

Dr Malte Janssen, Lecturer in Energy and Sustainability in the Science Policy Research Unit, University of Sussex Business School, said:

“The destruction of the Kakhovka Hydroelectric Power Plant has led to an immediate loss of 350 MW of hydro generation capacity in the region. In addition, the loss of the Kakhovka reservoir mean that the Zaporizhzhia Nuclear Power Plant is unable to operate. For the time being, this has minor effects on electricity generation, as the plant was shut down since its occupation. It is unlikely that there is an immediate danger for the Nuclear Power Plant from the lack of cooling, as it is most likely to rely on its cooling pond and atmospheric cooling towers to manage the residual decay heat of the shutdown reactors. However, the loss of cooling for the six reactors means that the plant will not be operational for the foreseeable future and means a long-term loss of approximately 13% of Ukraine’s electricity generation capacity.”

Prof Tom Scott, Professor of Materials and academic lead for Sellafield UK Centre of Expertise for Uranium and Reactive Metals, University of Bristol, said:

“Zaporizhzhia Nuclear Power Plant is safe, as the IAEA has said: there is a huge amount of water stored at ZNPP with its own full cooling pond, 18 more backup pools of water and 18 mobile pumping units. It needs very little water because all the reactors have been shut down for more than eight months. Based on our current understanding of the situation, the risks posed by this incident on ZNPP are actually very limited at this point in time.”

Dr Mohammad Heidarzadeh, senior lecturer in our Department of Architecture and Civil Engineering, University of Bath, said:

“The Kakhovka dam is one of the biggest dams in the world in terms of reservoir capacity, with an enormous reservoir water capacity of approximately 18 billion cubic meters. For comparison, it is 90 times bigger than the largest dam reservoir in the UK, which is Kielder dam in Northumberland. It is obvious that the failure of this dam will definitely have extensive long-term ecological and environmental negative consequences not only for Ukraine but for neighbouring countries and regions.

“From a structural point of view, the dam is an embankment (also known as earthfill) dam which means the dam is basically made of gravel and rock with a clay core in the middle as its water-sealing element. Sadly, these types of dams are extremely vulnerable, and are usually washed away quickly in case of a partial breach. And this is the reason that the dam is already completely washed away. Apparently the dam body was hit by some rockets during the Ukraine-Russia conflict, and experienced some partial damage, but only a partial damage is sufficient to cause a complete collapse of the dam because water flow can easily wash away the soil materials of the dam body in just a few hours. Rapid collapse of earthfill dams are seen several times in the past few decades.

“At this time, with the dam already collapsed, it is urgent that all parties focus on the mitigation efforts such as evacuations of downstream and saving lives, protecting communities by flood control methods, safeguarding water supply sources from contaminations, and restoring lifeline infrastructure such as roads, energy supply plants and hospitals.”

Prof Philip Thomas, Visiting Academic Professor, University of Bristol, said:

“The Zaporizhzhia Nuclear Power Station is upstream of the Kakhovka dam that has just been blown, and so will not be flooded.  All six reactors at the Zaporizhzhia Nuclear Power plant have been shut down for over 8 months, which means that their requirements for cooling water will be only a tiny fraction of what they needed when they were operating.  The engineers on site should be able to cope with low water levels in the Kakhovka reservoir.  There should not be concern for the safety of the nuclear power station at this time.”

Dr Mark Wenman, Reader in Nuclear Materials, Imperial College London, said:

“All 6 reactors at the plant are in a shut down state.  5/6 of these are in a state known as “cold shutdown” for many months meaning that the processes of radioactive decay in the fuel, which generates heat, can no longer heat the water in the cooling circuit and reactor vessel, to boiling point at atmospheric pressure.  In layman’s terms this means that the reactors are effectively self-sufficient in terms of water needed to cool them and it simply needs to be circulated around the system.  The 6th reactor is in warm shutdown state meaning it is a bit hotter and is being used to provide steam for use on site and possibly the local area.  Even this reactor will only need minimal cooling however.  Overall the risk to the plant or the fuel cooling ponds is very low indeed.”

Mr Jeremy Benn, Executive Chairman of JBA Group, and a member of the UK Reservoir Supervising Engineer panel, said:

“A catastrophic failure of a dam – whether deliberate or not – can lead to the sudden release of the stored water in the reservoir behind the dam. As part of the safety regime of a large dam, maps are usually prepared to show how high water levels may rise and how quickly. These are based on sophisticated computer modelling.

“In the current situation, the Ukrainian authorities are likely to have maps showing which areas could flood and so who needs to be warned or evacuated.

“This dam is concrete and so the initial breach will probably not widen significantly.”

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