Nikova

Rivers in the broader Idrija area originally flowed southeast towards the Hotenje Basin and the Ljubljanica river, but due to the karstification of the Ljubljana Basin and erosion of the Soča River, the rivers began to flow into the Soča river basin instead.^[1] The initial part of the Nikova River's course is a remnant of a former larger river that also shaped the Hleviše Saddles and reached the area of today's Zala stream east of Divje jezero. In the past, the river then continued to flow past Godovič pond and discharged into a larger river near Hotedršica. The former river cut through softer stratigraphic layers in the Zala fault area, while elsewhere it formed alongside of thrust faults. Nikova is believed to have played a significant role in the formation of a vadose zone, of which both Divje Lake and the Padarca stream are now part of.^[2]

Due to its course and limited self-purifying capacity, Nikova is the most heavily ecologically affected water body in the municipality of Idrija.^[3]

Nikova initially flows through shallow marine gray or white dolomite with dolomite conglomerate and sandstone, then predominantly through carbonate rocks, followed by shallow marine clastic rocks of shale and marl. As it flows through Idrija, it runs through shallow marine thin-layered limestone with dolomite interbeds, and a shorter section passes through deep-sea flysch with dark gray shale and quartz lenses just before its confluence.^[4] Nikova, like other surrounding rivers, took advantage of the faults of the Dinaric direction.^[2]