This habitat type is described in Ireland, where the original name ‘turlough’ refers to the temporary bodies of water in karstic limestone areas: lakes are formed when karst hollows fill with groundwater and water advances into the depressions in the ground. When the water level falls, the water is absorbed into the karst hollows again and the lakes dry up.
In the karstic limestone areas of Estonia, temporary water bodies with variable water levels can also be seen. They usually fill up in spring, when a lot of water flows out of the springs. Then, the water depth can be two metres and more; the water is very transparent, light, and hard (HCO3 content over 200 mg/l). In summer, karst lakes usually remain dry, so that their bottom resembles grasslands: there is moisture-loving vegetation, but there are also a few aquatic plants or open puddles . There are no fish in the temporary lakes, but there are rare invertebrates that are not found in permanent lakes.
We have the most karst lakes in the Pandivere Upland, the best known of them are Lakes Võhmetu, Lemküla, Piisupi, Mardihansu, and others. Karst lakes are usually located in groups close to each other and can join together in a water-rich year.