The Auranga originates near Soheda in a pass. It descends from the Ranchi plateau and pursues a winding course in a north-westerly direction for a distance of about 80 kilometres (50 mi), till it flows into the Koel near Kechki 16 kilometres (10 mi) south of Daltonganj.
It passes through a large valley, the southern face of which is formed by the Kumandih hills. Its bed widens rapidly and by the time it reaches the Palamu Fort it has attained a considerable size. Where the ruins of these two forts overlook it, the channel is crowded with huge masses of gneiss. Owing to its rocky bed, navigation is impossible in the rains, and at other times the supply of water is insufficient for even the smallest craft.