 It rises in the hills north of Painscastle, flowing initially to the southeast before turning to the southwest at Rhos-goch, assuming a more westerly direction at Painscastle then wrapping around the western end of the Begwns as it drops into a wooded gorge to join the River Wye as a left-bank tributary near to Erwood.Rain falling on the southern slopes of Llanbedr Hill and the northern slopes of the Begwns makes its way into the Bachawy.Much of the Bachawy's valley is developed in Silurian age mudstones and siltstones and parts are aligned with the Church Stretton Fault Zone.