WATER
SOTLA RIVER
The Sotla River forms the eastern boundary of the Kozjansko Regional Park and at the same time the national border.
- Source – southern slope of Macelj: 640m AMSL
- Outflow into the Sotla – Brežice: 134m AMSL
- Relative height difference: 506m
- River basin surface area: 581km2
- Length of the watercourse 90km
- Natural value: a hydrological, geomorphological, and zoological natural value of national importance
- Natura 2000 protected area: Sotla with tributaries (SI3000303)
Most of its basin (451km2) is in Slovenia, where it also receives its longer tributaries, the Bistrica, Mestinjščica, Dramlja, and Buča. In the middle reaches from Podčetrtek to Kunšperk, the river has created meanders in some sections, while in the lower reaches below the Zelenjak gorge, the Sotla used to meander across a wide flood plain before regulation, as evidenced by the course of the national border.
The diverse aquatic and riparian habitats provide a living environment for many species. The river is home to the thick shelled river mussel (Unio crassus) and the stone crayfish (Austropotamobius torrentium), the Eurasian beaver (Castor fiber), and the riverine vegetation is home to the otter (Lutra lutra).
In Sotla, 42 fish species have been recorded so far. Since it is an explicitly lowland river, it predominantly houses fish from the ray-finned fish order – carp (Cyprinus carpio), European chub (Leuciscus cephalus) and the common barbel (Barbus barbus). From other orders, there are also pike (Esox lucius) and the wels catfish (Silurus glanis). Of particular conservation importance are loaches (Cobitis), the lamprey (Eudontomyzon spp.), Italian roach (Rutilus pigus), European bitterling (Rhodeus sericeusamarus), and the Danube streber (Zingel streber).
BISTRICA RIVER
The Bistrica River and tributaries are a nature conservation value, part of a Natura 2000 site, and in its middle and lower reaches, the river follows the protected area of the Kozjansko Regional Park, with its catchment area in the Kozjansko and Obsotelje Biosphere Reserve.
The name of the river – Bistrica – suggests that it is fast-flowing, rises quickly and falls just as quickly, and clears up.
- Source – Glija Cave, Planinska vas: 480m AMSL
- Outfall into the Sotla River – Polje pri Bistrici: 180m AMSL
- Relative height difference: 300m
- River basin surface area: 108km2
- Length of the watercourse 32km
- Natural value: hydrological and ecosystem natural value of national importance