Cerknica Lake - Slovenia

Basic Information

Site Name: 

Cerknica Lake

Short name : 

Cerknica Lake

Country (Site Location): 


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Contact: Site Manager: 

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General Site Description: 

Lake Cerknica is intermittent lake appearing at the bottom of closed depression Cerkniško polje extending on the area of 38 km2. The karst features are associated with carbonate rock, both with limestone and dolomite. About 80 % of inflow consists of karst and only 15% of surface waters. The outflow is completely karstic. In spring and usually late in autumn the lake reaches normal level 550 m a.s.l., covering the area of 26 km2. Polje is flooded for 9 and dry for about 2 months, usually in summer. Lake Cerknica is a highly diverse ecosystem that changes in time and space. Vegetation pattern shows clear zonal distribution that depends on extent and frequency of flooding. The lake supports rich fauna with many endangered species, providing temporary shelters and food for protected large carnivores, such as brown bear, wolf, lynx and numerous species of water birds. In recent decades, flood and drought events have become increasingly irregular altering processes and conditions for many species.

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General Characteristics, Purpose, History

Site Status: 


Year Site Established: 


Size : 

3 800.00ha

Purpose of Site : 

Lake Cerknica is an intermittent lake with extreme water level fluctuations and longer aquatic phases in comparison to other wetlands. Increased occurrence of extremes regarding amounts and distribution of precipitation, and consequently changes in the water regimes in different water bodies need a deeper understanding of related processes. Therefore, Lake Cerknica can serve as a model system to study the effects of changing water levels on the associated biocoenoses. This is a basis for effective management practices of aquatic systems in changing environment.

History of Site: 

The “vanishing” lake has been inspiring the imagination of local people and visitors for centuries. Many of them believed that the lake was appearing and disappearing due to supernatural powers. The area has also been attracted by numerous researchers who tried to decipher the mystery of the lake. In 1551, Georg Wernher sent into print to Vienna his work De admirandis Hungariae aquis hypomnemation, which included a description of Cerkniško jezero (Simoniti, 2010). In the 17th century a belief that the intermittence was enabled by a system of underground lakes interconnected with the system of siphons was prevailing. The first detailed written information on the lake dates back to 1679, when Slovenian polymath J. V. Valvasor, a member of the English Royal Society, published an essay on the lake with a map of the area (Rupel, 1951). Due to this publication and many others describing the “extraordinary” ecosystem the lake became world famous. In 18th century Nagel and Gruber came to the simple conclusion that the lake appeared as a consequence of a surplus of water at the area (Kranjc 2002).

Research Topics: 


  • Lake during extreme flood; Archive of Notranjska Regional Park
  • Lake is fully covered by vegetation; Archive of Notranjska Regional Park
    Lake in summmer
  • Lake is surrounded by hills; Archive of Notranjska Regional Park
    lake with Javorniki
  • Sink hole in the bottom of the lake; Archive of Notranjska Regional Park
    Sink hole in dry season


Latitude: 45.445900000000
Longitude: 14.222000000000