The river is formed by the confluence of the Brerachan Water and the Allt Fearnach at Straloch, 3 miles (4.8 km) from the top of the strath. It flows past Kindrogan House and Enochdhu, where it takes in the Dirnanean Burn, and then through Kirkmichael. It flows on past Ballintuim and Bridge of Cally, half a mile south of which it joins the Black Water to form the River Ericht. The Ericht is a tributary of the River Isla, which in turn flows into the River Tay.
The name Ardle is derived from a Pictish warrior who was killed in battle fighting the Danes at Enochdhu in 903 AD. He was reputed to be a giant, and the mound of his supposed grave is located in the garden of Dirnanean Lodge in Enochdhu. It is 19 feet (5.8 m) long, and around 3 feet (0.91 m) wide. At its end is a 5-foot (1.5 m) high monolith. The origin of this stone is unknown but it is thought unlikely to be prehistoric.
- "Ardle, River". Gazetteer for Scotland. Retrieved 9 July 2010.
- "Ardle's Grave". CANMORE. Royal Commission on the Ancient and Historical Monuments of Scotland. Retrieved 9 July 2010.