Research shows high levels of minerals, including copper, zinc and cobalt, remain in the soil around the town of Kasese.
Though the Kilembe copper and cobalt mines ceased operations in western Uganda, the River Nyamwamba – the main water source for people in the area – is under threat of contamination.
Last year, geologist Alex Kwatampora was part of a team which found that harmful metals had washed down into the river from the mines.
"When we took samples from the effluents and indeed there are high levels of copper, some unacceptable levels of cobalt, zinc, nickel and these have effects to human beings," said Kwatampora.
The National Agriculture Research Institute reported that there's more contamination downstream, where the River Nyamwamba joins Lake George.
"I believe its copper turning these stones to a brownish colour and I think that is why people around this area are developing stomach illnesses," said Kasese resident Wasaka Maleu.
TRT World's Isabel Nakirya reports.