The Kerio River rises on the north slopes of the Amasya Hills to the west of Lake Bogoria.

[1] It flows northward through the Kerio Valley between Tugen Hills and Elgeyo Escarpment.

The Kerio and Turkwel contribute 98% of the river water flowing into Lake Turkana on Kenyan territory (which makes up only 2% of the total riverine inflow).

[3] The left bank of a 25 kilometres (16 mi) section of the river is in the South Turkana National Reserve.

[5] The main locations in Turkana District for irrigated agriculture are along the Turkwel and Kerio rivers.