It trickles out of the marshy Ondiri wetland in Kikuyu, Kiambu, with the whoosh of a fresh spring.

At 2,000 metres above the sea level and clear like the sky, it starts its southwest descent from the swamp decorated by reeds, green papyrus and water grass.

The slope of the swamp, shaped like a box funnel, helps gravity squeeze water out, as birds chirp away. It disappears below a bridge recently built for it on the Southern Bypass, to emerge on the other side as Nairobi River.

In its better days, Nairobi, the Kenyan capital, was "the place of cool waters". Its name, derived from the Maasai word enairobe, means "a stream of cold water". It is not the same stream today.

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