Relaxed 1.5km of flat from the dam down to the first (big) fall that most will portage. Easy grade 3 follows until a hard double drop immediately below a footbridge perched between two boulders. Grade 3/4 from this drop down to the takeout.
Head up to the Claerwen Reservoir (through Elan Village) from the A470 at Rhayader. The takeout is at a small bridge at the head of Caban-Coch Reservoir, and the putin is just below the Dam at the foot of Claerwen Reservoir itself.
Rainchasers is best experienced as an app.