Kherson is flooded for a second day following the destruction of a huge dam upstream of the city.

The first wave of evacuations, caused more by panic than by a real rise in water, broke off on Tuesday afternoon, says Oleg, a local volunteer who rescued residents in the Korabel ‘microdistrict’ – essentially an island that has been under constant fire from Russian artillery since November.

But on Wednesday morning, those living nearest the edge of the swollen Dnipro river found themselves trapped.

In Vorontsovskaya Street, flood levels rose several metres during the night, deluging the first floors of apartment buildings as much as 600 metres from the water’s edge.

Rescuers work here all day, taking locals to land by motor and rowing boats. Some have to be pulled out of the windows; evacuating bedridden patients is the most difficult thing as whole teams of rescuers have to be involved.

People take only their most valuable things with them – documents and pets. Rescuers work just as hard to evacuate animals as they do to save people.

To the north, in a residential area that descends to the Dnipro, a row of single-storey houses is underwater. Local resident Igor says he learned about the destruction of the dam from the news. “We thought that there would be a direct tsunami, ten-metre waves, like in a movie,” he said. “But the water was rising slowly all yesterday, and today even more slowly.” He points to part of a nearby roof barely sticking out from under the water.

His mother, 78-year-old Maria, recalls a similar flood from when she was five. “No one would ever think that something would destroy the dam,” she says. Igor laughs: “Mum, you seem to have forgotten to water the tomatoes.” They don’t want to leave the area, which is slowly sinking under water and is still under artillery fire.

The Kakhovska dam was destroyed in the early hours of Tuesday morning, causing water levels to rise by more than three metres that day and flooding 1,500 houses, according to Ukrainian prime minister Denys Shmyhal.

Ukraine’s government has accused Russia of being responsible for the destruction – which they have called an “ecocide” – and called for people living downstream to evacuate.

The dam had powered the Kakhovska hydroelectric plant, a major energy producer, and held back a reservoir of 18 cubic kilometres of water that feeds a canal carrying drinking water to Russian-occupied Crimea. Russia controls the east bank of the river, as well as the plant, while Ukraine controls the west bank.

Ukrhydroenergo, a Ukrainian state-owned enterprise that administers several major hydroelectric power stations along the Dnipro and Dniester rivers, said a detonation inside the dam’s engine room had taken place, that the Kakhovska dam had been completely destroyed and that the power station could not be restored.

Analysts have pointed out that the waters of the Kakhovska reservoir had reached unprecedentedly high levels prior to 6 June – possibly a result of negligence on Russia’s part and previous damage sustained by the dam.

The Kherson regional authorities announced an urgent evacuation. Inhabited areas downstream of the Dnipro river are still at risk of flooding, while the Crimean peninsula is at risk of being left without drinking water.

Ecologists have warned that the flooding of inhabited areas, private farms and infrastructure, including energy infrastructure, creates a significant pollution risk.

“Flooding of inhabited areas will most probably lead to contamination of the Dnipro water with sewage, household waste and fertilisers, and this means that water quality may deteriorate,” said Anna Ackermann, board member of the environmental organisation Ecodiya.

“The problem with water will definitely be very serious for thousands of people. [Another critical] issue is the issue of food security of the region itself – that is, what will people eat and grow. Over time, and in the absence of sufficient water [after the floods recede], the land simply degrades.”

But the real damage, experts say, will only be possible to assess when the water level steadies. That could take up to four days.

Immediate damage caused by the flood could be seen on numerous videos and photos appearing on the internet from both Ukrainian-controlled and Russian-occupied parts of Kherson.

Russian media outlets Meduza and MediaZona reported that, in Russian-occupied areas, residents were trapped on the roofs of houses pleading for help on local Telegram chats.

In a chat set up for facilitating evacuation from the city of Olseshky, about 70 kilometres downstream from the dam, one message read: “Please help! My parents are in the attic, they’re already sitting in the water and the water is still coming… They have no more drinking water. They are pensioners. My mum is recovering from a stroke and used to work as a doctor in the village! SOS!” openDemocracy has not been able to verify the authenticity of the message.

Ukrainian volunteers are collecting money and aid so they can use inflatable boats to help save people on flooded occupied territory. Russian news website ASTRA, however, reports that Russian armed forces are blocking volunteers’ access to flooded areas.

Ukraine’s national nuclear energy company Energoatom said the detonation at the Kakhovska dam ‘could have negative consequences’ for the occupied Zaporizhzhia nuclear power plant, which is Europe’s biggest, but that the situation was ‘under control’. Ukraine has also “lost one of its major sources of renewable energy… with a capacity of 334.8 megawatts that cannot be restored,” said Svitlana Romanko, director of Ukrainian organisation Razom We Stand.

Mykhailo Podolyak, adviser to the head of the President’s Office, said on Twitter he believed Russia had blown up the Kakhovska dam to try to hinder the Ukrainian army’s offensive. (The army has insisted damage to the plant will not prevent its efforts to liberate occupied territories.)

The Russian-backed authorities in the occupied Kherson region initially denied that the plant was damaged, but later claimed it had been partly destroyed by Ukrainian shelling.