[4] The name Colapis, recorded in antiquity, is presumed to have come from the Proto-Indo-European roots *quel- 'turn, meander' and *ap- 'water', meaning 'meandering water'.

[5] The Kupa originates in Croatia in the mountainous region of Gorski Kotar, northeast of Rijeka, in the area of Risnjak National Park.

It flows a few kilometers eastwards, receives the small Čabranka River from the left, before reaching the Slovenian border.

The section from Stari Trg down to Fučkovci since 2006 is part of the Slovenian Krajinski park Kolpa nature reserve.

The hydrological parameters of the Kupa are regularly monitored at Radenci, Kamanje, Karlovac, Jamnička Kiselica and Farkašić.