Medard, Artificial lake in Habartov, Czech Republic

Medard is an artificial lake northwest of Sokolov, between Svatava and Habartov, formed by flooding the Medard–Libík coal pit. It covers 493 ha, reaches a maximum depth of 50 m and holds about 50 million m³, making it the largest lake in the Czech Republic.

Brown coal mining at this site stopped in 2000, leaving behind a huge excavated depression. About eight years later, water began filling the depression and transformed it into this body of water.

The villages of Čistá u Svatavy, Dvory, Kolonie Hahnemannova, Kytlice and Lísková were demolished as the Medard and Libík pits expanded and merged. In April 2018, a hundred families from the region planted an avenue of a hundred oaks above the shore, called Alejí přátelství (Avenue of Friendship), to mark the centenary of Czechoslovakia; actor Marek Eben planted one of the trees. The avenue won the 2018 Alej roku poll organised by the NGO Arnika.

You can swim, bike, and do water sports here, as the shore has several dedicated zones for each activity. It is helpful to check in advance which areas are open and where you can best access the activity you want to do.

The lake is meromictic: its deep layer, the monimolimnion, does not mix with the surface and holds dissolved heavy metals and metalloids. This latent pollution limits some planned uses such as diving and fishing and calls for science-based management of the water.