While Bohinj may be the largest permanent lake in Slovenia, Cerknica is the largest intermittent lake. If you’ve never heard of an intermittent lake, you’re in good company. Neither had I until I came to Slovenia. Let’s pay a visit to find out what this means…
What is the size of Cerknica, and how does it disappear?
The lake’s normal size is around 26 square kilometres, or 10 square miles. During dry periods, the lake, which has a mean depth of only 6.1m (20ft), drains into the underground karst reservoirs from which it is fed. When these fill up during rainy periods, usually in autumn, the lake reappears quite rapidly, and can even inundate the surrounding area.
Even more interestingly, the intermittent nature of the lake is unpredictable. It can disappear for as long as a year (although this is rare), and appear suddenly almost without warning. Some of the reservoirs from which it is fed lie above lake level, and these fill up quickly during rainy periods only to drain out into the lower reservoirs and fill the lake.
Visiting the Lake
The lake (when present) is a popular spot for fishing and canoeing. It is possible to arrange a canoe safari expedition which includes a visit to some exciting karst cave systems. There are many hiking and cycling trails around the lake, and it is a haven for wetland birds. In fact the whole area is rich in biodiversity. There is a small museum, café and visitor centre where you can find lots of itineraries, and learn more about the lake.
It is also interesting to visit the lake during dry periods and witness the amphibious vegetation. I would love to actually witness its appearance or disappearance, but I guess you’d have to be either local or lucky to be there at the right time. If I ever get to see this, I’ll be sure to take a video!
Lake Cerknica is a 45-minute drive from Ljubljana, or around one hour from Koper if you are leaving from the coast.