River Dragonja: a flysch valley and seasonal waterfalls

Updated October 16, 2026.

The Dragonja has cut a valley of cascades and pools into north-western Istria’s flysch hills. Summer drought and rain change its water levels and waterfalls.

Softer marl and harder sandstone

The Dragonja is 28 kilometres long. Its upper course consists of a network of streams in Slovenian Istria. At Škrline, the Velika Rokava, also called the Dragonja, meets the Mala Rokava, also known as the Pinjevec.

Flysch contains alternating layers of softer marl and harder sandstone. Water wears them away at different rates, creating steps over which it falls in cascades. The river has also formed meanders, pools and gravel bars in the valley.

Waterfalls and changing water levels

Parts of the Dragonja often dry up in summer. Heavy winter rain can raise water levels quickly and flood the surrounding land. Permanent springs in the lower course provide additional water.

Well-known sites include Škrline and the waterfalls on the Pasjok tributary and the Supot stream below Koštabona. They lie in different parts of the river network.

Mills, fields and the way to the sea

Mills once worked beside the river, with 22 recorded at the end of the 19th century. The clustered villages stand on higher ground to avoid flooding. Cultivated slopes on the right bank are partly terraced and supported by stone walls.

The lower course crosses drained farmland in the Croatian-Slovenian border area. Here, people diverted the Dragonja into the St Odoric canal, which runs along the southern edge of the Sečovlje salt pans to the Gulf of Piran. The Drnica follows the old river channel towards the sea.