The Pivka river originates in the karst basin of Pivšče near Zagorje, which contains several karst springs, the most important of which is the Pivšče karst spring. This spring has a walled shaft that served as a local source of drinking water until the construction of a water supply system from the Malni pumping station.

The term pivka refers to a sinkhole that drinks water, a small lake that drains slowly, or hayfields near Zagorje where the ground drinks water and the riverbed runs.

When there is a lot of water, we can see the Pivka river slowly meandering through the landscape; otherwise, its bed is dry. It created the world-famous Postojna Cave.

After 26 kilometres, the river Pivka sinks into the Postojna Cave, one of Slovenia’s longest cave systems and our most visited tourist cave.

Surface waters, as well as groundwater, flow from Upper Pivka into two seas: the Pivka river into the Black Sea and the Reka river into the Adriatic Sea.

Palško jezero Lake is the largest of all Pivka lakes. When the lake is full, there is enough space for 300 football fields. In terms of medium water level, Palško jezero lake is comparable to lake Bled, and measures nearly twice as much in extremely large lakes.

Petelinjsko jezero lake appears for the longest time. The water can stay in it for up to 9 months, as evidenced by the appearance of two extremely large lakes in 2014.

Because the Pivka intermittent lakes frequently dry up, there are no fish. The Karst fairy shrimp (Chirocephalus croaticus), a small crayfish, lives in two of the lakes.

More about Pivka intermittent lakes

The Municipality of Pivka has the most lakes in Slovenia, but the majority of them are not visible at all times. The lakes are intermittent.

The Seasonal Lakes of Pivka Nature Park gets its name from the fact that the majority of the Pivka lakes (11 out of 17) are located in the municipality of Pivka. Within the municipality, the Nature Park also includes Upper Pivka and Javorniki. Outside of the Nature Park, there are five lakes in the municipality of Ilirska Bistrica and one in the municipality of Postojna. The municipal border, and thus the Nature Park’s border, runs right along the hollow of Kljunov ribnik; the higher part of the hollow, known as Mali dol, is owned by the municipality of Ilirska Bistrica.

The Seasonal Lakes of Pivka Nature Park borders the Notranjska Regional Park in the municipality of Cerknica on the east, and both are part of the karst Ljubljanica river basin. The Nature Park extends over the Tabor ridge at the foot of the Košana valley and Brkini on the west side, where it already forms part of the influential area of the Škocjan Caves Regional Park (Reka river basin).

The Seasonal lakes of Pivka Nature Park contained 142 natural values.

14 of the 17 Pivka lakes have natural value status, with Palško jezero and Petelinjsko jezero lakes being natural values of national importance.

The endemic karst crayfish (Chirocephalus croaticus) is only found in Petelinjsko jezero Lake and its surroundings, and nowhere else on the planet.

Natural enemies of olm or proteus (Proteus anguinus) are only found in springs, where they can be preyed upon by large fish. This species is at the top of the groundwater food chain and is primarily threatened by pollution from sinking rivers.

There used to be 13 mills and sawmills on the Pivka river.

The basins of Palško jezero Lake and Petelinjsko jezero Lake served as military training grounds for the Yugoslav People’s Army. The bottom of Petelinjsko jezero Lake has been reshaped with larger and smaller grenade holes, as well as a larger ditch and several smaller ditches, and the bottom of Palško jezero Lake has been rehabilitated.

In the wider area of the intermittent Pivka lakes, approximately 90 caves have been registered and explored. Some of them provided shelter to Stone Age man (e.g., Parska Golobina, Betalov spodmol, Otoška Jama, Jama v Lozi, etc.).