Lake Cerknica

We tried to go hiking this weekend at Lake Cerknica, which is the largest seasonal karst lake in Slovenia. We had stopped there last summer on one of our trips to Ljubljana and have been wanting to go back because there were nice trails around the lake, and also because it is supposed to be one of the best birding spots in Slovenia. One thing we didn't take into consideration, however, was that karst lakes are generally dry in summer and flooded in winter. And as you know if you've been reading our blog...this has been no ordinary winter in terms of rain!

The flooding around the town of Cerknica was terrible. See that building in the water at the end of the road? That is the coffee bar we had planned to relax in after our hike around the lake. Needless to say we didn't have any coffee. Or a hike. The flooding had turned the whole valley into a giant lake. The reason the flooding was so bad is pretty interesting. Karst lakes are not fed by above-ground rivers like most of the lakes we all know. Instead, they are formed when groundwater levels rise high enough to force the water above the surface, which usually happens in winter. In summer, the lakes go dry as any water quickly drains through the karst rocks - an example of these rocks is on the right. So while these seasonal lakes are supposed to form in winter, when there's too much rain the lakes can fill up quickly like bathtubs and flood the entire landscape until there is someplace for all that water to go.

So we couldn't hike, but we were able to watch some birds anyway. The high water levels created opportunities for birds to feed on the debris piled up on the water's edge like this very cooperative Black Redstart. So even though the rain foiled our plans once again we still ended up with a lovely sunny day in Slovenia.