The Athi River starts in the iconic Ngong Hills that rise above Nairobi. It flows past the bustling metropolis and through Kenya’s largest national park, Tsavo East, until it finally reaches the Indian Ocean. The river, its tributaries and riverbanks are the source of irrigation and drinking water for millions of people, and wildlife. Its water and riverside also underpin a number of industries in the region, including mining and tourism.

However, a local environmental group, the Explorer’s Club of Kenya, is concerned about this important river system. Signs are strong that human activity and pollution are overriding the river’s natural capacity to provide clean water for purposes such as drinking, agriculture or wildlife habitat. In some places, farmers have abandoned their fields, and certain species of birds and other wildlife are noticeably absent.

The group organized a walking expedition along the river to find out more about the state of its waters, and document potential sources of its pollution to find solutions to reverse the degradation….