Concerned environmentalists now want relevant authorities to act on a Presidential directive to clean up River Athi which feeds into the mega Thwake Dam that is currently under construction in Makueni County.

An Environmental Ambassador Silas Wameyo on Thursday said the silence among government agencies since the Presidential pronouncement was deafening adding that “time to act was now”.

"The silence on Thwake Dam clean up is deafening! When the former President Uhuru Kenyatta visited the dam, he ordered an urgent clean up of Athi River which is the main river that will contribute most of the water inflow into the dam," Mr Wameyo told AVDelta News in an interview.

He said the problem is that Athi River is critically polluted and will fill Thwake Dam with water that is semblance of wastewater or sewage.

"Such water will be smelly and unfit for human consumption whether it is used for irrigation agriculture or fisheries," Mr Wameyo said.

He said Athi water being used in Galana Kulalu Irrigation project is suitable for irrigation though it is still from Athi but this was due to the distance from Nairobi which was the main source of pollution.

Mr Wameyo said water is purified by natural systems as it flows for a long distance in the river.

He observed that this isn't possible with the Thwake case because the dam is upstream and very near to the point source of pollution namely Nairobi city and Athi River Town.

"Time to act is now! Let's map out all the point sources of pollution to Athi River. These include factories that drain their waste into the river, All informal settlements within the Riparian zone which are within a radius of 30 metres from the river must be pulled down," he added.

Mr Wameyo added that building tree barriers between settlements and the river as the late Environment Minister John Michuki did in parts of Nairobi also known as 'Michuki Park' would help curb pollution of the river.

"Unfortunately time is running out. We must act now to save not only Thwake Dam, but also the water users downstream across the country," he added.