Cerknica lake phenomenon

An example of Valvasor’s scientific approach

Tu pride flash
The seasonally disappearing and reappearing Cerknica Lake generated a great deal of scholarly interest before Valvasor made the attempt to investigate the phenomenon. Unlike his predecessors he was aware that the only way to solve the mystery was patient work in the field. In two years, as he reports, he saw with his own eyes all the stages of the filling and emptying of the lake; he carefully recorded the local names for caves and sinkholes and accurately noted the order in which the water flowed away and how long it took. Valvasor also prepared a drawing of the Cerknica Basin with water level at the lake's largest extent and together with its natural science and physics dimensions his work gained great cultural and historical weight.

Valvasor described in detail the way the local population made use of the waters of the lake, by catching fish when waters drained away and cultivating the lake bottom during the short summer season. Some of his observations were highly humorous as he described the inhabitants rushing naked and without shame into the receding waters to catch as many fish as possible.

Valvasor also made conclusions about the phenomenon that were shrewd and largely correct. We are drawn by his description of the Velika and Mala Bobnarica (Great and Little Drummer) sinkholes from where rumbling and drumming can be heard from under the ground; the writer astutely concludes that below the ground these sinkholes are probably connected to sinkholes in the nearby hills and that the rumbling noise from the emptying or empty lake must travel from one end of the underground tunnels to the other, His phenomenon also brought him to the explanation of the system of syphons.