As the river moves through Kenya's capital Nairobi, the clear water turns black.
And large birds feed on dead animals alongside.
The Nairobi River crosses Kibera, a neighborhood of nearly 200,000 poor people.
It goes near several factories that make clothes, alcohol, and building materials.
Environmentalists have accused them of releasing untreated wastewater and other pollutants like oil, plastic and glass into the water.
Experts and locals fear the water is harming plants in nearby farms that feed many Kenyans.
Community groups help clean up the river and the government is increasing its efforts.
But families in the quickly growing suburb of Athi River, some 30 kilometers away, say they can no longer depend on the water.
Anne Nduta is a mother of two babies.
At times, she uses the river's dark waters to wash her children's clothes by hand.
"When it rains, the Athi River water is usually full of garbage, when it clears a bit we use it to wash clothes," said Nduta.
"But as the dry season continues, the water becomes darker in color and we have to start buying expensive... water."
A 20-liter can of water sells for 20 shillings, or $0.16.
Nduta would need four of them to wash her babies' clothes every three days.
Morris Mutunga grows vegetables like kale, spinach and amaranth on his farm in the Athi River area.
He has watched crops like French beans shrink when he used water from the river.
"I wish those polluting this river upstream in Nairobi could stop for the sake of food security in our country," he said.
The area is the source of many vegetables sold in Nairobi markets.
Stephen Obiero is a scientist who studies organisms and the environment.
He said that waste in the river used to water farmland could expose plant products to bacteria and viruses.
The problems start further up the river.
Violet Ahuga says her family defecates in bags and throws them in the river because they cannot pay to use modern toilets.
She said, "I know what I'm doing is pollution, but there's no other way because I cannot afford the 850-shilling (about $6.85) monthly toilet fee."
Besides, many unofficial housing areas also direct their wastewater lines straight into the river.
The settlements have open trenches where people pour dirty water that flows into the river.
Kenya's new national government says it is trying to clean up the river.
The government has formed a group to clean up and protect the river.
But the group has no budget and is yet to meet.
The National Environment Management Authority (NEMA) is responsible for overseeing the river's water quality.
Some Kenyan lawmakers have accused the agency of letting industries get away with polluting the river.
Research groups have found high levels of heavy metals, like lead, barium, iron, aluminum, zinc and copper, along the river.
Alex Okaru is a public health expert at the University of Nairobi.
Okuru said if people drank the water, high levels of heavy metals could cause health effects such as liver and kidney damage.
NEMA chief David Ongare told The Associated Press that few companies are being charged because the government is working with industries to deal with pollution.
He said businesses are asking NEMA for help to follow its rules.
And the agency follows all reported incidents of pollution.
He added that the agency has also been watching companies with past pollution problems.
And he said that if any continue to have problems action would be taken.
Locals and community groups say a way to clean up the river would be to provide modern toilets at little or no cost.
In Kibera, an organization called Mazingira Yetu, Swahili for Our Environment, is working with the government to build 19 modern toilets.
The organization's co-founder, Sam Dindi, said they also wanted to prevent plastic and other waste from being dropped in the river.
Plastic waste could be reused and organic waste, Dindi said, could turn into fertilizer.
I'm Dan Novak.