The River Nith rises about a kilometre south west of Enoch Hill. It flows northward under the B741 at Nith Lodge roughly halfway between Dalmellington and New Cumnock before swinging eastward. From New Cumnock it forms the boundary between the Lowther Hills and Carsphairn/Scaur Hills. The A76 travels down the valley created by it (Nithsdale). Just north of Thornhill is Drumlanrig Castle belonging to the Duke of Buccleuch.