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Cerknica Lake
by Natasa Pavsek

In the heart of the Notranjska, the most distinct Karst landscape in Slovenia, amidst a polje (Karst field) sheltered from the south-west by the densely wooded Javorniki Hills, lies the illustrious Cerknica Lake. It is an intermittent lake, filled up mostly by the autumn rains and the early spring thaw, which dries up in May or June, sometimes even in mid-winter. The lake gets its water from Karst springs bubbling up at its edge, while the water flows out underground, through sinkholes. Its surface level varies by over 7 metres (it lies between 546 and 553 metres above sea level). When the water is low, it spans over 20 square kilometres but when high waters set in, it is over 10 kilometres long, almost 5 kilometres wide, its surface area exceeding 30 square kilometres.

The filling up is the most interesting phase in the lake's life cycle. Water starts bursting forth from vent holes, the streams rise immediately and flood the field at the bottom of the valley. When the lake starts receding, the water disappears into picturesque sinkholes amidst the fields and into swallow-holes, the entrances to the hollow Karst underground embellished with stalagmites and stalactites. Some of the outflow water resurfaces at Mo?ilnik, the source of the Ljubljanica river. The lake is an important fish habitat as well as a nesting ground for many species of birds. It is increasingly popular as a recreational area, ideal for fishing, hiking, nature excursions (speleology), wind surfing, swimming and ice-skating, depending on the season and the water level. The constantly changing landscape makes it worthwhile to visit it in any season.

Stories about the miraculous lake have for centuries inspired artists whose vivid imagination transformed it into a fable about the divine and unfathomable; Dante Alighieri saw it this way in his Divine Comedy. The lake won worldwide fame when the intermittence mechanism was first described over 300 years ago by the Slovene polymath, historian, topographer, ethnographer and sketcher, Baron Janez Vajkard Valvasor (1641-1693), which earned him membership of the British Royal Society. He also published a lengthy summary of his description in his most comprehensive work, The Glory of the Duchy of Carniola.

Article abstracted from Sinfo.