This sub-catchment consists of the area drained by the Crocodile River and its two main tributaries, the Elands and Pienaars Rivers , from the area immediately to the north of the City of Johannesburg , to its confluence with the Limpopo River .

The Pienaars River drains the area from Pretoria northwards to the Waterberg Mountains near the town of Warmbaths .  All these rivers are perennial and their flows are supplemented by substantial discharges of treated domestic and industrial effluent.  Flows in these rivers are also enhanced by water imported from the Vaal River system to the south of Johannesburg , which is used principally for domestic and industrial water supplies prior to treatment and discharge. (Ref 2)