Lake · Slovenia
Lake Cerknica
Lake Cerknica is a lake in south-western Slovenia that comes and goes. In wet times it floods a wide basin with water, and in dry summers it can drain away completely.
Picture credit: Martin Windischhofer (Public domain) · Bob Ramsak (CC BY-SA 4.0) · JožeStražišar (CC BY 4.0) · Wikimedia Commons
Where is Lake Cerknica?
Countries on its shores: Slovenia.
Largest lake of: Slovenia.
Middle of the lake: 45.75° N, 14.39° E
The story behind it
The ground under Lake Cerknica is karst: rock full of holes, cracks and caves. Through many openings, the lake is connected to caverns deep underground. When heavy rain falls in autumn, water gushes up through these holes and quickly floods the basin. When the weather stays dry, the water drains away through the same holes. Then farmers make hay and let their animals graze on the dry lake bed. Sometimes the lake stays dry for more than a year, as it did in 1834–35. Even the fish disappear with the water and come back when it returns! When it is full, Lake Cerknica is the largest lake in Slovenia. More than 300 years ago, in 1687, the scholar Johann Weikhard von Valvasor described this puzzling lake to the Royal Society, a famous club of scientists. Today many kinds of birds nest here, and the lake is a protected wetland.
Find it on the globe
Lake Cerknica is there as a small blue dot with its name, right on the water. From far away the planet is only a blue ball; detail arrives as you zoom in, and this one appears once you are close enough. Open it on the globe.
It sits at its real coordinates, not near them — the same numbers listed in the facts above. Switch off the layer for this kind of place and it disappears again; the buttons for that are down the right-hand edge.
Questions children ask
How big is Lake Cerknica?
When it is full, Lake Cerknica covers up to about 38 km², which makes it the largest lake in Slovenia. Often it is smaller, about 26 km², and in dry summers it can drain away completely.
Where does the water go?
The water sinks through many holes in the ground into caves and hollows below the lake. After heavy rain, water comes back up through the holes and the lake fills again, sometimes very quickly.
What do people do at the lake?
When the lake is full, people go rowing and do other water sports, and late autumn is the best time for fishing. When it is dry, farmers make hay and let their animals graze on the lake bed.
Where these numbers come from
Every figure on this page was checked against public reference sources before publication. Where sources genuinely disagree, the text says so.
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