The Tonalli River rises on the eastern alopes of Mount Marrup within the Tonalli Range in remote country within the Greater Blue Mountains AreaWorld Heritage Site, and flows generally east southeast, east northeast, and then east southeast, before reaching its confluence with the Wollondilly River within Lake Burragorang in Yerranderie State Conservation Area. The river descends 559 metres (1,834 ft) over its 26-kilometre (16 mi) course.[2]