The Nonaya is a smaller tributary in the Nalón system, slate-fed and spate-responsive. The upper reaches show pure slate character in step-pool confines; the descent is rapid. The water remains amber-toned throughout. The Nonaya maintains its steep spate character throughout its reach. The available pools are secondary to the river's responsive descent. The wading demands respect throughout.

Wading: Wet quartzite slabs in gorge reaches

In the mountain-to-sea trout rivers of Asturias, olives and other mayflies do much of the work in spring whenever levels and colour allow, followed by strong evening caddis and steady buzzer life through early and mid-summer, with terrestrials and mixed surface food from wooded, pastoral banks rounding out the diet whenever flows drop back into safe wading range.