Flowing through the waters of the once-mighty Kafue River – a source of drinking water and livelihood for millions of Zambians – is poison.

Since the start of the year, four copper mining companies operating in the Southern African nation, including one British and three Chinese firms, have been accused of releasing toxic mining waste into the Kafue River’s watershed in one of the country’s worst environmental disasters.

The most devastating spill occurred on February 18, when the tailings dam holding mining waste from Chinese company Sino-Metals Leach Zambia burst its walls and released 50 million litres of acidic effluent into the river.

The pollution killed fish, burned maize and groundnut crops and led to the deaths of livestock, wiping out livelihoods and deepening the plight of struggling farmers. In the days following the spill, the water supply to the nearby town of Kitwe was shut down.

The spills have sparked outrage across Zambia at a time when the government is planning to quadruple production of copper – a mineral critical to the energy transition – to three million tonnes a year by 2031 to capture a share of the boom driven by rising demand for electric vehicles worldwide.

Copper mining is a cornerstone of the Zambian economy. In recent years, the government has sought to woo international investors to develop its resources, with Chinese companies making some of the biggest investments in its mining sector.

“A pattern of gross corporate negligence”

Environmental advocates have accused the companies of reckless mining practices that prioritised profits over safety, and a systemic failure of the government to protect both people and the environment.

“The environmental impact of this pollution is catastrophic,” said Raymond Mutale, Transparency International Zambia’s acting executive director. “Residents are witnessing their livelihoods being washed away with the toxic water, and yet those responsible continue to operate with impunity.”

Environment minister Collins Nzovu described Sino-Metals’ acid spill as “a serious environmental disaster that could have been avoided if proper safety measures were in place”.

He announced that a multi-agency task force will investigate the spill, assess damages and enforce penalties. “We will ensure that those responsible face the full force of the law, and we are reviewing current environmental regulations to prevent future occurrences,” he said.

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A coalition of environmental justice organisations has called on the government to prosecute the Chinese companies for environmental crimes. The coalition decried a “pattern of gross corporate negligence and inadequacies in environmental compliance, oversight and enforcement” and called for urgent reforms of the mining sector.

“Should mining expand within the current status quo and modus operandi, citizens and the environment are at risk of widespread disasters such as those recently reported,” it warned in a joint statement.

The Kafue River turns toxic

When the dam holding Sino-Metals’ mining waste (known as tailings) collapsed, Nsama Musonda Kearns, executive director of the Care for Nature Zambia NGO, rushed to the spill site. She described “a devastating sight” and “people in shock” as the murky acidic waters flooded homes in the nearby Kalusale area.

“People unknowingly drank contaminated water and ate affected maize. Now many are suffering from headaches, coughs, diarrhea, muscle cramps and even sores on their legs,” she told Climate Home News. The community fears having to find alternative farm land to survive, she added.

Around 60% of Zambia’s population of 20 million people depend on the Kafue River for irrigation, fishing and industrial use. The river, which is a major tributary of the Zambezi – one of Africa’s longest-flowing rivers – supplies drinking water for five million people, including to its capital Lusaka.

Structural flaws at the Sino-Metals tailings dam

The Engineering Institution of Zambia (EIZ), the body which regulates engineering practices in the country, dispatched a team of senior engineers to investigate the dam’s collapse.

A preliminary investigation revealed flaws in the dam’s design, approval and operational processes, the institution’s president Wesley Kaluba told Climate Home.

“The team also observed cracks, uncompacted walls and inconsistent wall thickness, which raises concerns about the integrity of the structure,” Kaluba said, adding that there was “insufficient evidence” to confirm whether the infrastructure was operated by qualified and licensed engineers.

Kaluba warned that any EIZ members found to have contributed to the incident will face disciplinary action in line with the institution’s code of conduct.

Sino-Metals has apologised for the environmental disaster and the harm caused to local communities and committed to remedy the situation by cleaning up the river and helping restore people’s livelihoods. Mining activity remains suspended.

Profits over environmental safety

Unfortunately, the acid spill at the Sino-Metals mine is not an isolated incident.

In January, a toxic spill at the Mimbula Mine, owned by British company Moxico Resources, contaminated nearby water sources. Local residents reported severe water pollution, with rivers turning a reddish-brown colour and emanating a strong chemical odour.

“The Mimbula spill is yet another example of how mining companies prioritise profits over environmental safety,” said environmental lawyer Gloria Mulenga. “Without stricter enforcement, these disasters will continue to endanger lives and livelihoods.”

Moxico Resources did not respond to a request for comment.

Elsewhere in Copperbelt Province, the director of a mine operated by Rongxing Investments was arrested this month after the Chinese company reportedly ignored a government order to halt its activities following the death of a worker, who allegedly fell into a pool of acid, and extensiv