The Great Kei catchment is a single fan shaped catchment draining an area bounded by the Amatola mountain range in the south, the Winterberg in the east and the Stormberg / Drakensberg range to the north of Queenstown at an altitude of 2400 masl. In the east the catchment is bounded by undulating hills running in a north-south direction to the coast separating the Kei catchment from the Mbashe catchment. (Ref 1)

The area is characterised by the picturesque Great Kei River valley, which is some 400 m below the surrounding plateau. On the left and right banks the valley rises steeply to meet the coastal plateau zone, which covers most of this sub-area. The Gcuwa River has its headwaters at the inland edge of this coastal plateau zone at 1200 masl. The topography of the Gcuwa River valley is undulating from its headwaters through to Butterworth before it steepens and enters the Great Kei River. The Kubusi River has its headwaters in the Amatola mountains above Stutterheim and meanders through the coastal plateau before falling away steeply to enter the Great Kei River. The coastal zone area comprises a very small section of the catchment around Kei Mouth. (Ref 1)