The Swart-Kei is a highland river originating in the Stormberg Mountains of South Africa's Eastern Cape Province, flowing at elevations beginning around 1,500 meters before joining the Wit-Kei to form the Great Kei River at approximately 540 meters elevation. As one of the source tributaries of the Great Kei system, the Swart-Kei drains through the Amatolo-Winterberg Highlands, a region recognized as the southern extent of the montane-escarpment aquatic zone. The river passes through Albany thicket and forest biomes characteristic of the Eastern Cape interior, making it a distinctive highland waterway with a rich freshwater fish fauna representing both "Cape" and "Karroid" fish species assemblages.