The North Koel rises on the Ranchi plateau and enters Palamau division, below Netarhat near Rud. After flowing nearly due west for about 32 kilometres (20 mi), it turns north at an almost complete right angle through a gorge at Kutku, and flows through the centre of the district until it falls into the Son a few miles north-west of Haidarnagar.
From its source to its junction with the Son its length is about 260 kilometres (160 mi), and since it drains a catchment area of at least 9,100 square kilometres (3,500 sq mi), it naturally contributes a large supply of water to the Son during the rains; at other times the stream is not deep enough to enable cargo boats of even small dimensions to make their way up to Daltonganj. In many places the reaches of this river present scene of great beauty and sometimes even of grandeur, such as the rocky bed and rapids north of Hutar and the gorge at Kutku.
Mention may be made of the metamorphic rocks which form the watershed between the North Koel and the Damodar to the west of the Chandwa-Balumath road.
The principal tributaries are the Auranga and the Amanat, both of which join it from the east, the former at Kechki, 16 kilometres (10 mi) south and the latter 8 kilometres (5 mi) north of Daltonganj. Another tributary is the Burha, which joins the North Koel above Kutku at Bagechampa.
The North Koel project is being implemented at Mandal near Kutku. The project has a 64.82-metre (212.7 ft) high dam, from which water will be released for picking up by the Mohammadganj Barrage and Indrapuri Barrage. Hydro-electric power generation would be 2 x 12 MW. The project would flood 15 villages, of which 5 are within the Palamau Tiger Reserve.