Major Soča system tributary and marble trout river in its own right, less touristed than the Soča itself. Clear limestone water with excellent marble trout, brown trout and grayling. Good dry fly fishing during caddis and olive hatches — a river that offers the Soča experience with more solitude.
The Idrijca runs 60 km from the Vojsko plateau springs at roughly 924 m to its confluence with the Soča at Most na Soči, draining around 600 km² of windward Julian Alps karst. The upper river cuts confined, bedrock-walled step-pool and gorge sequences through Triassic limestone and dolomite above Idrija; the middle valley relaxes into partly-confined pool-riffle on dolomite cobble where Permian greywackes and red sandstones introduce a slightly softer lithology; and the lower reach to Most na Soči returns to dolomite-dominated runs and glides. Bedload is mostly stable, well-armoured carbonate cobble, and the water carries the same emerald cast as its parent Soča. The legacy mercury signature from Idrija's five-century cinnabar mine still rides the fine fraction of the bed, mobilised on every major spate.
Wading: Polished carbonate bedrock ledges and algal biofilm in the upper gorge reaches
- River
- Limestone
- Partly confined
- Step pool
- Bedrock gorge
