Chad Medicine Horn starts each day mopping his bedroom floor and bleaching the walls to kill the fresh black mould.

A few hours later, the floor is once again soaked by groundwater seeping into the converted basement that he shares with his four-year-old grandson. They spend afternoons trying to stop the murky water soaking their double bed and few surviving clothes and toys with squeegee mops donated by the Red Cross.

Upstairs, Chad’s mother, Christina Selvin, 75, spends most days on the couch in pain from arthritis and kidney cancer, too sick to escape the toxic mould spores.

“No matter how much I clean, this shit just keeps coming back, it’s ruined all our stuff,” said Medicine Horn, 50, while mopping. “This isn’t healthy, everything stinks, my eyes hurt, we’ve all been sick, it can’t be legal to leave us living like this.”

It’s been like this for nine months in the White Swan community on the Yankton Sioux reservation in South Dakota, where hundreds of Native Americans have been struggling to cope with unprecedented rainfall and disease outbreaks following a series of extreme weather events.

Facebook Twitter Pinterest The annual powwow and ball tournament in White Swan had to be cancelled this year because of the flooding. Photograph: Amber Bracken/The Guardian

These climate catastrophes have triggered three federal major disaster declarations for the state, but help has been slow to arrive to this tribal community where severe flooding has compounded longstanding social and economic inequalities by wrecking jobs, homes, and infrastructure.

And while tribal authorities scramble to navigate bureaucratic grants to ease the immediate suffering, fears are mounting about the community’s future: further flooding is forecast for spring which threatens to turn White Swan residents into climate refugees.

“The floods have caused a lot of hardships, it feels like the third world,” Shelly Saunsoci, 43, director of the Tribal Employment Rights Office (Tore), told the Guardian. The unemployment rate is 85% and few folks have insurance.

If we have another wet winter and spring, there will be devastation, we’ll have to be evacuated. Shelly Saunsoci

“The climate is changing, it’s already snowing in Montana, and if we have another wet winter and spring, there will be devastation, we’ll have to be evacuated,” she added.

The Yankton Sioux is one of seven tribes in South Dakota, where a third or so of the 9,000 enrolled members living within its territory near the Nebraska border – mostly in federal public housing projects managed by the tribal housing authority (THA).

Historically, White Swan was located on the banks of the Missouri River, but in 1952, the community was flooded out by the newly constructed Fort Randall dam.

Facebook Twitter Pinterest Shelly Saunsoci, who is the vice-chair of the community and the tribal employment rights director, in White Swan. ‘We feel like we are all alone.’ Photograph: Amber Bracken/The Guardian

It was rebuilt in the 1960s on the southern edge of Lake Andes in Charles Mix county, with a powwow arena for traditional festivities situated between the houses and water.

After several years of low water levels, the lake has been flooded since early March when a bomb cyclone – heavy snow, wind and rain – hit the area. The ageing aqueduct, which should divert excess water from the lake to the Missouri River, was overwhelmed by the extreme rainfall. (Until the water recedes, full inspections are impossible.)

In White Swan, groundwater and waste flowed into basements as the sewage station neared collapse; the highway and powwow arena were inundated.

A month later, another cyclone struck, followed by a second consecutive summer of record rainfall, causing havoc for local farmers already struggling due to the president’s trade wars.

Facebook Twitter Pinterest Houses made uninhabitable by the flooding in White Swan, South Dakota. Photograph: Amber Bracken/The Guardian

One of the most visible consequences of global heating is the increased frequency and intensity of extreme weather events like heatwaves, heavy rain and storms, which wreak economic and social havoc on communities.

Gordon White Bull, 41, was rushed to hospital with liver failure during the first downpours in March, and returned four months later still recovering from a transplant. Back home, the family car was wrecked on the muddy road, while the furniture, children’s clothes and kitchen cabinet doors were covered in so much mould that they had to be thrown out.

“I can feel it in my lungs, it’s hard to breathe. We’ve done our best to keep it clean, but we need to get out,” said White Bull, 41, who was recently hospitalized again with a stomach infection. The basement is submerged in several inches of water, and the putrid smell makes it hard to breathe or see clearly.

Left: The basement of Theresa Hart’s house in White Swan. A sump pump works around the clock but still the water seeps up. Photographs by Amber Bracken/The Guardian Left: The basement of Theresa Hart’s house in White Swan. A sump pump works around the clock but still the water seeps up. Right: Mold and moisture collect on the walls in Deonne Tibbetts’ house in White Swan. Photographs by Amber Bracken/The Guardian

“Mould kills lung tissue and repeated infections can affect child growth and development, people should not be living in these dangerous conditions,” said Tom Gilmore, a retired physician who spent 50 years working on Indian reservations. “But Native Americans are not politically important.”

Initially, even tribal authorities were slow to react, though eventually they provided sump pumps (bought with donations from another tribe) and organised “muck squads” to strip mouldy walls and clear the wreckage.

I can feel it in my lungs, it’s hard to breathe. Gordon White Bull

But the rain kept lashing down, and the lake kept rising. In early August, the annual powwow was cancelled for the first time ever.

That’s when a group of women took matters into their own hands.

Saunsoci rallied local church groups, the Salvation Army and Red Cross, who brought emergency supplies – bedding, cots, tents, toiletries, food and clean-up kits (mops, gloves, bleach and face masks) – to the community centre which became the hub for exhausted families.

Facebook Twitter Pinterest Volunteer Joan Jones at the community centre in Swan Lake. Photograph: Amber Bracken/The Guardian

Joan Jones, 58, resigned from her job to deal with the crisis full time. “I had to choose between the children and my home, or my job, I couldn’t keep doing both. We were exhausted, we felt forgotten, but setting up the centre helped bring us together, it’s the one good thing that came of this disaster.”

Jones and other female elders help run the relief effort, organizing donations and hot meals for the children, many of whom suffered recurrent infectious diseases like impetigo, ringworm and diarrhea. One little girl, Harmony, 6, was recently hospitalized with multiple skin and stomach infections, and still has the telltale ringworm marks across both cheeks.

The community rallied, but record rainfall in September brought further misery: children waded through waist-high water as more waste leaked into people’s homes and gardens, while farms and sewage systems flooded across the county. The highway flooded again – just a couple of weeks after a $1m state-funded project to raise it was completed – and remains closed.

Soon after, Deonne Tibbetts fled to her sister’s overcrowded apartment in a nearby town with her husband and four children, after the two youngest, aged two and four, contracted skin infections that wouldn’t clear up. “They were on antibiotics but bathing in foul smelly water and surrounded by mould, I had to get them out so they could heal,” said Tibbetts, 29.

E coli bacteria has been detected in stagnant water pools on the reservation and nearby town, but state and tribal environmental officials insist that the tap water is safe.

In September, the tribe’s request for help from the national guard was denied. So they filled sandbags to construct flood defence walls around the lake, community centre and Tore office. A few weeks later, they built an earth berm around the southern edge of the lake, and organized a social media campaign to pressure state officials.

Left: Volunteers Theresa Hart, left and Christine Medicine Horn sort clothes at the community centre in White Swan. Right: Kids stop by the community centre for food and a drink. Photographs by Amber Bracken/The Guardian Left: Volunteers Theresa Hart, left and Christine Medicine Horn sort clothes at the community centre in White Swan. Right: Kids stop by the community centre for food and a drink. Photographs by Amber Bracken/The Guardian

Some families have received cash grants, including Chad Medicine Horn’s mother, Christine Selvin, who used $214 from Fema, and $500 from Red Cross to replace the flood-damaged washer-dryer and buy clothes for great grandson Gabe.

But scores of families continue to live in desperate conditions.

The governor and Fema deny claims the community was abandoned, and say work with the tribe is ongoing. “[Since June] State and Fema personnel have canvassed the Lake Andes area and White Swan community on foot, knocking on doors to ensure that everyone affected had the opportunity to apply for the assistance available to them. Any affected families who wanted to relocate were instructed to work with tribal housing officials to start that process,” said Kristin Wileman, press secretary to the Republican governor, Kristi Noem.

Facebook Twitter Pinterest Kids playing basketball in White Swan. Photograph: Amber Bracken

The reservation had a housing crisis even before the floods, according to tribal authorities. Currently in White Swan, 27 of the 64 houses are considered unfit for habitation, but affordable rentals are scarce and the THA’s 50 empty properties require renovation or demolishment having tested positive for crystal meth. (South Dakota’s meth epidemic is especially severe among tribal nations.)

A few clean-ups were expedited thanks to a donation from a California tribe. But, White Swan residents are extremely reluctant to be rehoused in renovated “meth houses” since a gas explosion last month killed Aurora Denney, 24, and her daughter Natalice, 3, soon after they moved in.

Last week, the tribe welcomed news that the reservation was included in the latest federal disaster declaration covering the September floods – paving the way for individual claims and tribal applications for disaster planning, infrastructure projects and reimbursement for repairs.

Facebook Twitter Pinterest Flowers and candles form a memorial at a house that exploded, killing a mother and her child, in a tribal housing project in Wagner, South Dakota. The family had relocated from White Swan due to flooding days earlier. Photograph: Amber Bracken/The Guardian

The Yankton Sioux, like most sovereign tribal nations, operates on a shoestring budget – a situation that has worsened under the Trump administration. Next year’s proposed budget allocates $1.9bn to the Bureau of Indian Affairs – a 35% cut since 2017.

But help will be slow, and in White Swan, life was tough even before the climate crisis hit them hard.

“We’re poor people, trying to do our best, but when the snow and ice melts, I don’t know what we’ll do,” said Medicine Horn, who’s been unable to work since suffering road traffic accident almost 20 years ago. “My mom’s sick but we’ve got no place else to go. We come from beautiful people, but it’s not easy being native.”