The source of the approximately 60 km-long river is
Lough Sillan near
Shercock from which it flows westwards through Lough Tacker, and south of
Cootehill, until it reaches
Butlersbridge. To the west of the village the river then flows through a series of lakes, before its confluence with the
River Erne.
Tributaries The
Bunnoe and Laragh Rivers are two main tributaries that join the river below Cootehill, where it is also joined by the Dromore River. Other tributaries include the Knappagh, Madabawn and Cavan Rivers.
Volumes The flow or discharge of the river is measured in its lower reaches at Butlersbridge, river levels are also measured at Rathkenny and Derryheen Bridge. The
catchment area to the
gauging station at Butlersbridge is , which with an annual average rainfall of , yields an average flow of . The maximum recorded flow between 1955 and 2012 was on 30 November 1995. ==Etymology==