life spans as they rapidly fill with sediments. Lake Ohrid is being infilled at its north end by its modest main tributaries, but is preserved by its great depth, by continuing tectonic subsidence, and by the main inflows being by underground karstic channels from Lake Prespa carrying minimal sediment. The graben system is still tectonically active and Lake Ohrid sits in a seismogenic landscape, with many visible traces including fresh fault scarps, displaced sediment and soil sequences, stepped hillsides, and a hydrothermal field near Kosel. Moderate earthquakes are frequent, with the strongest yet measured here on 18 February 1911, with a magnitude 6.6 at a focal depth of 15 km, destroying houses but with no loss of life Hydrology The lake drains an area of around 2,600 km² and is fed primarily by underground springs on the eastern shore (about 50% of total inflow), with roughly 25% shares from rivers and direct precipitation. Over 20% of the lake's water comes from nearby Lake Prespa, about to the southeast and at 150 m higher altitude than Lake Ohrid. The water leaves Lake Prespa trickling through underground watercourses in the karstic landscape, where it is joined by mountain range precipitation and eventually emerges in numerous springs along the eastern shore and below the water surface of Lake Ohrid. The water leaves Lake Ohrid by evaporation (~40%) and through its only outlet, the Black Drin River, which flows in a northerly direction into Albania and thus to the Adriatic Sea. The relatively dry, Mediterranean climate and the small drainage basin of 2,600 km² (catchment/lake surface ratio of ~7) of Lake Ohrid results in a long hydraulic residence time scale of ~70 yr. Physical and geochemical properties The water at the surface of Lake Ohrid moves predominantly in a counter-clockwise direction along the shore, as a result of wind forcing and the Earth rotation, similar to the Ekman-phenomenon known from oceans. In terms of vertical water exchange, convective mixing during winter cooling is the dominant process. However, in an average winter only the top 150–200 meters of the lake are mixed, whereas the water below is stably stratified by salinity. The stability due to this salinity gradient allows complete convective mixing events only roughly once every 7 years. Both in terms of nutrient concentration (4.5 μg L−1 of phosphorus), as well as biological parameters Lake Ohrid qualifies as oligotrophic. Thanks to this oligotrophy and