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:

existing

Year Site Established:

2008

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:

Parameters:

Photos

Lake during extreme flood; Archive of Notranjska Regional Park

Lake is fully covered by vegetation; Archive of Notranjska Regional Park

Geographic

Coordinates:

Latitude: 45.445900000000
Longitude: 14.222000000000

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Site Details

Ecosystem and Environmental Characteristics

Elevation Range FROM:

536.00msl

Elevation Range TO:

551.00msl

Elevation - Average:

546.00msl

Temperature Range (Monthly Minimum) FROM:

-5.00°C

Temperature Range (Monthly Maximum) TO :

25.00°C

Temperature: Average Annual:

8.00°C

Precipitation Minimum Monthly :

110.00mm

Precipitation Annual :

1 700.00mm

Precipitation Maximum Monthly :

200.00mm

Biome :

Fresh Water Lakes

GEO-BON Biome:

Fresh water lakes

Ecosystem and Land Use:

Lakes
Fresh Water Lakes

Biogeographic Region:

Continental

Geology:

Lake Cerknica is an intermittent lake appearing at the bottom of Cerkniško polje. In the southern part of Slovenia runs a long depression in the NW - SE direction, from Ljubljana Swamp to the Kolpa River valley. In this depression, a series of karst poljes is located, Cerkniško polje being the largest among them. Depression has been formed along one of the most important tectonic lines in Slovenia, the Idrija fault. Cerkniško polje consists of carbonate rocks, Mesozoic limestones and dolomites. A part of the polje s bottom and the NE slopes are composed of less karstified Triassic dolomites. Other parts consist of Jurassic and Cretaceous limestones. Cerkniško polje itself lies about 40 m deep at the bottom of the depression, result of the corrosion. The Plesitocene climatic changes are reflected in the sedimentation and erosion of alluvial sediments.

Hydrology:

Lake Cerknica belongs to the Ljubljanica river basin, which has pluvio-nival hydrological regime with slightly Mediterranian variation. Water is collected from the upstream lying karst poljes, from the surrounding karst plateaux, as well as directly from Cerkniško polje s rainfall. The catchment area of Lake Cerknica covers about 475 km2. The region receives about 1700 to 1800 mm of precipitation per year, with evapotranspiration reaching 750 mm. 80% of the lake´s inflow consists of karst waters, and 15% of surface waters. The outflow is completely karst-like, i.e. underground. For a little more than 9 months per year the polje´s floor is flooded, creating a lake, and for little more than 2 months it is dry.

Vegetation:

Plant communities in the wider area of Cerkniško polje, i.e. in the area influenced by frequent floods or on its edge where floods occur only during extremely high waters, consist from aquatic, amphibious wetland communities and communities of mires and wet grasslands. Wood vegetation on the southern part of the lake consists from the association Omphalodo-Fagetum. Warmer sites are overgrown with submontane woodland Hacquetio-Fagetum var. geogr. Geranium nodosum. Sites with more extreme environmental conditions are covered with the associations Querco-Ostryetum and Genisto januensis-Pinetum sylvestris. The narrower area of Cerkniško polje is covered by grasslands, wetlands, bogs, etc.

Soils:

Lake Cerknica is neither a lake neither a typical wetland. It is locus typicus for intermittent lakes and karts poljes. The succession of the ecosystem is continuously disturbed by the water level fluctuations, droughts and floods. These pulse disturbances present a physical factor, which is of vital importance for the lake, influencing the abiotic and biotic processes, i.e. mineral cycling and life histories, and productivity of organisms resulting in a variety of habitats and species.

eLTER Parameters

eLTER Parameters:

- Groundwater
  - Water quality
- Biodiversity (following the Essential Biodiversity Variables approach)
  - Rivers and Lakes

Network Affiliation

Networks/Projects:

LTER
eLTER catalogue
Natura 2000
Ramsar

Site Type (Spatial Design):

Complex Site

Short name :

Cerknica Lake

LTER related

LTER Site Code:

LTER_EU_SI_002_002

LTER Site Classification/Category:

Emerging

Protection Status and Resource Management

Natura 2000 site

75 - 100%

Management of Resources :

Yes

Management of Resources - Percent of Site:

25 - 50%

Design and Scale of Site

Scale of Observation:

beyond catchment

Design of Observation:

mainly observation

Scale of Experiments:

beyond catchment scale

Design of Experiments:

no experimentation

Infrastructure

Value of the Infrastructure :

Less than 50 k

Accessible All Year :

Yes

All parts of Site Accessible:

Access Type:

boat

Permanent Power Supply:

Infrastructure:

Energy and data infrastructure › Data transmission › Data Transmission Type (within site) › No within site data transmission
Data infrastructure › Data storage › Proprietary file format

Operation

Operations Cost:

Less than 10 k

Permanent Operation:

Sampling Interval:

Every 365 days

Maintenance Interval: