Environmentalists warn that these pollutants threaten the health of aquatic species and residents who rely on the river for drinking water. Additionally, water hyacinth obstructs the river flow near the lake.
As rivers worldwide face pollution threats, environmentalists say it is crucial to manage and protect them carefully to ensure sustainability, especially as they flow into major water bodies like Lake Victoria, the world's second-largest freshwater lake.
Ecologist Patrick Odhiambo from Ecology Without Borders states that polluted rivers flowing into Lake Victoria pose a significant threat to marine biodiversity. He emphasizes that marine life is at risk from plastic waste and toxic chemicals, which can impair their biological functions.
Odhiambo highlights the urgent need for action to prevent further ecosystem degradation. "We need to take immediate action to control pollution from industries, agricultural activities, and residential areas to save our marine biodiversity," he said.
River Kibos has been the center of controversy, with residents protesting against pollution. They blame nearby industries for discharging effluent into the river.
Activist Boniface Akatch urges authorities to regulate waste disposal and ensure compliance with environmental standards to protect public health and the environment.
"Much more needs to be done to protect the river as many livelihoods depend on it," Mr Akatch said.
Investigations in Nyalenda slums along River Auji reveal that raw sewage is released directly into the river. Resident John Omollo laments the unbearable conditions and the authorities' failure to address their concerns.
"It is uncertain when this cycle of impunity will come to an end," Mr Omollo said.
Kisumu County's National Environment Management Authority Director Tom Togo is concerned about the alarming levels of raw sewage discharged into River Auji, which also runs through the Manyatta informal settlement.
Mr Togo identifies poor waste management as another issue, stating that aquatic life is dying due to pollution and a pungent odour permeates the river.
"The living organisms in these rivers are dead because the water is highly polluted that cannot sustain life," he said.
Despite the challenges, Togo acknowledges progress in water pollution control, with many facilities complying with waste management policies.
"There is remarkable improvement, and we are on a constant lookout for companies and industries that pollute our waterways."
He recommends improving sewer lines in the slums to address the problem, emphasizing the importance of extending sewer lines to curb illegal waste discharge.
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Climate change has also exacerbated pollution issues with the Kisumu Water and Sanitation Company (Kiwasco) forced to make temporary cuts in water use.
In February and March, Kiwasco Managing Director Thomas Odongo revealed that the Kajulu water treatment plant, which abstracts water from River Kibos, is operating below capacity due to low water levels. He warned that water bowsers many be needed if the situation persists.