Mr Bojo Leju worked for eight years for the oil consortium Greater Pioneer Operating Company (GPOC), a joint venture between Malaysian, Indian and Chinese oil companies – with South Sudan’s government owning 5%.

After a major pipeline rupture five years ago, he started photographing and filming pools of oily water and heaps of blackened soil in locations in Unity State, including sites near Roriak, where the herders live.

He says spills from oil wells and pipelines were “a ordinary status”, and that he was involved in transporting contaminated soil away from roads, so it would not be seen.

He tried to raise his concerns with company managers, but he says little was done and “there was once refuse remedy plan for ground”.

Mr Bojo Leju additionally says “produced H2O” – water released from the ground when oil is extracted and often containing hydrocarbons and other pollutants – was not properly treated.

There were reports of high oil content, above international standards, in the produced water “each past in our morning assembly”, he says, “and this H2O is injected again into the surrounding”.

“The query is the place does H2O current?” he says.

“As much as the river, as much as the H2O supply the place nation drink, as much as ponds the place nation catch fish.”

Mr Bojo Leju explains that “one of the vital oil chemical compounds seeped ill” into the groundwater, where they will flow into boreholes.

“The H2O desk is infected,” he says.

When intense rains began in 2019, earth dykes were put around some spilled oil “however it was once no longer plethora to resist the quantity of H2O”, he adds.

In Roriak, there is no data available about the quality of the water the herders drink, but they fear pollution is making their cattle sick.

They say calves have been born without heads or without limbs.

Unity State’s agriculture minister blames the deaths of more than 100,000 cattle in the last two years on the floods combined with oil pollution.

In a forest close to Roriak, a group of men and women chop down trees to make charcoal.

They have walked for eight hours along dirt roads flanked by flood water to reach the forest.

They say the only water they can find here is polluted.

Even boiled “it reasons diarrhoea and belly ache”, says one woman, Nyakal.

Another, Nyeda, wipes away tears, saying she needs the charcoal to sell, but is worried about her seven children, left with her mother for a week.

“She has not anything both,” she says.

Nyeda lives near the state capital, Bentiu, in a reed hut squeezed into a camp housing 140,000 people who have fled conflict or the floods. It is completely surrounded by flood water and protected only by earth dykes.

There is some food aid, but many in the area survive by foraging for water lily roots and fish to supplement their rations.

Safe water is scarce. Nyeda uses water from a borehole for washing and cooking, but needs money to buy drinking water.

Health professionals and politicians in the area have told the BBC they fear pollution and the lack of clean water are taking a toll on human health.

In a hospital in Bentiu, a mother has just given birth. Her new-born baby’s nose and mouth are joined.

“They have got refuse get entry to to wash H2O,” says Dr Samuel Puot, one of the doctors caring for the baby.

“They simply drink from the river the place H2O and oil are blended. That could be the sickness.”

He says there are “many” cases of children born with abnormalities, such as no limbs or a small head, in Bentiu and also Ruweng, an oil-producing area north of Unity State.

They often die within days or months, he adds.

Genetic testing can give clues about the causes of congenital abnormalities, but the hospital does not have the facilities, and results are often not conclusive.

Dr Puot wants the government to keep a register of cases.

As the data is not recorded systematically, it is not clear whether these anecdotal reports indicate an unusually high prevalence of congenital abnormalities.

“It’s believable that oil-related air pollution may give a contribution to an greater chance of delivery defects,” says Dr Nicole Deziel, an environmental health specialist at Yale University.

Environmental pollution is a risk factor for congenital abnormalities, alongside genetics, maternal age, infection and nutrition, she says.

Some compounds released during the production of oil can affect foetal development, Dr Deziel adds.

“Anecdotal experiences can grant as noteceable signs of environmental condition issues,” she says, but stresses that without systematic data collection, establishing evidence of a causal relationship is difficult.

In 2014 and 2017, the German-based non-governmental organisation Sign of Hope carried out peer-reviewed studies close to other oil fields in Unity State.

They found increased salinity and high concentrations of heavy metals in water nearer oil wells, as well as high concentrations of lead and barium in human hair samples.

The researchers concluded these were indicators of pollution from oil production.

“Speaking about oil is like touching the guts of the federal government,” says Mr Bojo Leju.

He spoke to the BBC in Sweden, where he has been granted asylum.

In 2020 he was approached by South Sudanese lawyers who wanted to sue the government over oil pollution.

He agreed to testify as a witness. But he says security personnel detained him, hit him on the head with a pistol and forced him to sign a document recanting his evidence.

He fled the country soon afterwards. The lawyers did not pursue their case.

The BBC asked the oil consortium GPOC and the South Sudanese president’s office to comment on the allegations in this report, but they did not respond.

Scientists are not sure whether the floods in Unity State will ever recede.

Dr Chris Funk, director of the Climate Hazards Center at University of Carolina, Santa Barbara, says 2019 saw record sea surface temperatures in the west Indian Ocean, which “would had been unattainable in a global with out state exchange”.

Warmer air can hold more moisture, and he says there was a “robust hyperlink” between these sea temperatures and the 2019 extreme rains over East Africa.

Dr Funk says higher rainfall has continued since then over the Lake Victoria basin that feeds into South Sudan, but it is not clear whether this is a permanent new pattern.

Temperatures in South Sudan have risen and are expected to rise further, he adds.

This means extreme precipitation “will likely be extra closing” and, under some global warming scenarios, heat and humidity could mean some parts of the country “would no longer be habitable”, he says.

However, despite the floods and pollution fears, many here hope to return to a life of raising animals and living off the land.

In Roriak, children fashion a miniature village out of the clay on the ground, complete with model huts and cows.

And near Bentiu, an elderly woman grinds water lily roots next to the flood water. She says she would like to a have a cow again, one day.

“When the H2O is going ill, I’ll develop grain, even though it’s years,” she provides.