The disaster directly affected four oblasts, or regions: Kherson, Mykolaiv, Dnipropetrovsk and Zaporizhia. In Kherson, downstream, the immediate toll was greatest. The province has been a crucial theatre in the war. Russia captured much of it soon after the invasion, but in November 2022 its forces were pushed back to the eastern bank of the Dnieper river, which bisects the region. After the dam’s collapse, flooding caused havoc.

Kakhovka reservoir

Kakhovka dam

Dnieper River

Nova Kakhovka

Korsunka

Ukrainian-controlled

Russian-controlled

Oleshky

Kherson

3 km

Google, © 2022 Maxar Technologies

The dam was around 30 metres high and 3.2km long. The explosion probably happened close to its base. Before the blast high rainfall had filled the reservoir to record levels. The flood covered 83,000 hectares, an area roughly the size of Kyiv, Ukraine’s capital.

The Russian-held eastern bank was worst affected. Oleshky, which had a population of 16,000, was almost submerged. Residents, many of whom escaped to their roofs, waited days for help.

Floods reached Kherson, 58km downstream. Ukraine had liberated the city in November 2022 after six months of Russian occupation. The district of Ostriv, meaning island, in the middle of the Dnieper, was especially badly damaged.

Within days the water receded, but the damage was still becoming clear. Lyubov, whose house in Kherson was flooded, says that at first the authorities took an interest in assessing the damage, but that now there is little talk of rebuilding or overhauling the ruined homes. Today on the gates of derelict houses in Kherson are the phone numbers of the owners who have abandoned them. The UN estimates that up to a million people were left without drinking water. Cities to the north of the reservoir in Dnipropetrovsk, including Kryvyi Rih and Nikopol, were badly affected. Many people still face shortages, though a new pipeline is reportedly nearly complete.

The loss of the reservoir also hurt southern Ukraine’s agriculture. The lake supplied irrigation systems in Dnipropetrovsk, Kherson and Zaporizhia, which, along with Mykolaiv, contained around 25% of Ukraine’s cultivated farmland. Dozens of wells were dug as make-shift alternatives, but many farms can only hope for rain. The loss of irrigation could reduce crop yields by 70%. Farming was already dangerous in Kherson. Retreating Russian troops sowed fields with mines. This, combined with the water problems, stopped many people from returning to the fields after the flood.

The broader environmental effects added to the devastation. The disaster is thought to have damaged nearly half a million hectares of protected land and water habitats, killing thousands of animals and birds. Water tainted by petrol, sewage and other pollutants quickly reached the Black Sea. By mid-June Ukrainian scientists said the contaminated water covered more than 7,300 square km, and was approaching the mouth of the Danube in Romania. Upstream, meanwhile, mussels and other creatures that had previously helped to filter the reservoir’s water rotted.

Mr Zelensky has described Russia’s bombing of the dam as an “ecocide”. Ukrainian investigators are collecting environmental evidence as part of a war-crimes case that they are bringing before the International Criminal Court. Yet some scientists have expressed surprise at how quickly areas have recovered. To understand this optimism, look upstream to the former reservoir.

“I thought that at least for the first few months after the draining of the reservoir there would be no permanent vegetation, maybe some local vegetation, but not the permanent cover of poplars and willows,” says Bohdan Kuchenko of Ecoaction, an environmental group. The green recovery has led some to argue that the reservoir should never return. Among them is Oleg Dyakov of Rewilding Ukraine, an NGO. Before the war, his organisation identified the Dnieper delta and estuary as an area of potential for restoring long-lost wildlife. Now he believes refilling the reservoir would waste an opportunity. Within three to five years, he thinks, a “mosaic landscape” of forest, reed-beds and shallow lakes could form.

Such arguments often draw on a sense of historical injustice. To build the reservoir, Soviet engineers destroyed an area known as Velykyy Luh, or “Great Meadow”, a diverse landscape that spread across the tributaries, forests and marshes. Cossacks, totemic figures in the Ukrainian national imagination, lived off the fertile soil between the 16th and 18th centuries. A new reservoir, the theory goes, would repeat the damage that the Soviets inflicted on Ukraine’s cultural heritage.

Turning back the centuries, however, may be impossible. Some researchers note that climate change will make the region dryer. That could halt the growth of vegetation, and put more pressure on irrigation systems. Some scientists have proposed building a smaller reservoir to give more space to nature. Another idea is to construct a series of mini-reservoirs (the original Kakhovka HPP was itself in a large cascade of facilities along the Dnieper). Mr Kuchenko says that “a huge reservoir” and power plant is no longer necessary; electricity could be generated from other sustainable sources such as solar or wind.

Some in Ukraine’s energy sector are sceptical. There is “no alternative” to rebuilding the dam and reservoir, says Oleksandr Kharchenko of the Energy Industry Research Centre, a think-tank in Kyiv. He suggests that a large hydropower capacity will be important for restoring Ukraine’s energy system following Russian attacks on infrastructure, and for the transition to renewable energy.

Then there is the Zaporizhia nuclear power plant, which is under Russian occupation on the eastern bank of the river. It used the reservoir to cool its reactors, which are currently in shutdown modes. Following the dam blast the plant had to rely on an artificial lake until its staff dug wells to boost supply. Mr Kharchenko says that turning the plant on after the war would require the reservoir’s return.

Ukraine’s government has suggested that it plans to rebuild the HPP when possible. In March it issued a decree stating that the reservoir bed could not be used for any other purpose for up to five years after the end of martial law, which remains in force.

Still, two main factors complicate any reconstruction plans. The first is money. Rebuilding the HPP will cost nearly $1bn, according to the Kyiv School of Economics. The broader reconstruction costs, which cover housing, agriculture, sanitation and more, are estimated to be over $5bn. Yet these figures can only be understood in the context of Ukraine’s reconstruction costs as a whole. Those have now reached $486bn, according to the World Bank, $75bn more than its estimate in March 2023.

The scale of the task will force Ukraine and its partners to use their limited resources carefully. The construction of a vast new reservoir may have to wait. One Ukrainian hydrologist points to the Dnipro HPP, the country’s largest, which is upriver in Zaporizhia and was badly damaged by an air strike in March. Repairing that, he says, is more urgent than rebuilding Kakhovka.