Lake Ohrid is a lake which straddles the mountainous border between the southwestern part of North Macedonia and eastern Albania. It is one of Europe's deepest and oldest lakes, with a unique aquatic ecosystem of worldwide importance, with more than 200 endemic species.
North Macedonia's side of Lake Ohrid was declared a World Heritage Site by UNESCO in 1979, with the site being extended to also include the cultural and historic area of Ohrid in 1980. In 2010, NASA named one of Titan's lakes after it. In 2014, the Ohrid-Prespa Transboundary Reserve between Albania and North Macedonia was added to UNESCO's World Network of Biosphere Reserves. Albania's side of Lake Ohrid was also designated UNESCO world heritage status in 2019. North Macedonia's portion was designated as a protected Ramsar site in 2021, passing all nine criteria for proclamation.Ministry of Environment and Physical Planning (2021) "Ramsar Information Sheet: Lake Ohrid". Ramsar Secretariat, Gland, Switzerland.
In Albania, the coastal portion of the lake holds Managed Nature Reserve status. In North Macedonia, a portion of the lakeside is part of the Galičica National Park.
The towns situated at the lakeside are Ohrid and Struga in North Macedonia along with Pogradec in Albania. The lake is otherwise surrounded by settlements in the form of villages and resorts in both basin countries.
Geography
Lake Ohrid is one of the oldest lakes in the world, and with a maximum depth of and mean depth of , it is the deepest lake in the Balkans. It covers an area of and contains an estimated 55.49 cubic kilometres ( million acre-feet) of water. The lake is long and wide at its maximum extent, with a shoreline of .
64% of Lake Ohrid's shoreline and 69% of its surface area are within North Macedonia, whereas 36% of the shoreline and 31% of the surface area fall within Albania.
Origin
The Ohrid and Prespa Lakes are the two largest in a north–south chain of tectonic basins (grabens) including the Korçë basin, and Lake Ioannina in northwestern Greece, known as the Dessaret group. The transition from compressional to extensional tectonics in the central Balkan Mts occurred around 6 million years ago, with the oldest lake sediments being Pliocene, possibly 3-5 million years old.Hoffmann et al. 2010 Evolution of ancient Lake Ohrid: a tectonic perspective. Biogeosciences, 7, 3377–3386, www.biogeosciences.net/7/3377/2010/doi:10.5194/bg-7-3377-2010/ The Dessaret chain is a poorly developed rift valley. Worldwide, rift valley lakes with similarly ancient origins include Lake Baikal, Lake Titicaca, Lake Tanganyika and the Dead Sea. Most lakes have much shorter 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 from 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.Hoffman et al. 2010
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.Z. Spirkovski, Z. Krstanovski, L. Selfo, M. Sanxhaku, V.I. Puka, "The Monitoring Programme of the Lake Ohrid Conservation Project", in Transboundary Water Resources in the Balkans: Initiating a Sustainable Co-Operative Network, ed. Jacques Ganoulis, I L Murphy, Mitja Brilly (Springer, 2000)A. Matzinger, Z. Spirkovski, S. Patceva, A. Wüest, "Sensitivity of ancient Lake Ohrid to local anthropogenic impacts and global warming" (Journal of Great Lakes Research 2006, 32: 158–179)A. Matzinger, M. Jordanoski, E. Veljanoska-Sarafiloska, M. Sturm, B. Müller, A. Wüest, "Is Lake Prespa jeopardizing the ecosystem of ancient Lake Ohrid?" (Hydrobiologia 2006, 553: 89–109)
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.S. D. Hadzisce, "The mixo-phenomenon of Lake Ohrid in the course of the years 1941/42-1964/65 (in German)" (Proceedings of the International Association of Theoretical and Applied Limnology 1966, 16: 134–138)
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 the filtered spring inflows, the water is exceptionally clear with transparencies to a depth of as much as 22 meters (66 feet). Lake Ohrid lacks an annual deep water exchange which in other lakes can bring complete overturn; plunging rivers are also absent. Despite this, dissolved oxygen never drops below ~6 mg L−1.A. Matzinger, M. Schmid, E. Veljanoska-Sarafiloska, S. Patceva, D. Guseska, B. Wagner, B. Müller, M. Sturm, A. Wüest, M. Watzin, V. Puka, T. B. Naumoski (eds), "Lake Ohrid and its watershed, state of the environment report" (Lake Ohrid Conservation Project. Tirana, Albania and Ohrid, Macedonia)
Wetland habitats Previously extensive wetland habitats in the vicinity of Lake Ohrid have been lost due to conversion into agricultural or urban land. These include Struga Marsh, large portions of which were drained for agriculture in the 1940s and again in the 1960s when the River Sateska was rerouted.Deutsche Gesellschaft für Internationale Zusammenarbeit (2015) Initial Characterisation of Lakes Prespa, Ohrid and Shodra/Skadar. Implementing the EU Water Framework Directive in South-Eastern Europe .
Nowadays, the last remaining significant coastline wetland at Lake Ohrid is Studenchishte Marsh, which is located on the eastern shore near the city of Ohrid. Despite degradation from a variety of sources such as large-scale disposal of construction waste, major land conversion, disruption of water connections to Lake Ohrid, beach urbanization and loss of reed belts, Studenchishte Marsh is still an important buffer to prevent lake eutrophication and a key habitat for biodiversity, including relict plants and endemic species. These values, and the comparative rareness of similar habitats in Macedonia (now North Macedonia), prompted an expert team in 2012 to recommend designation of a 63.97-hectare area at Studenchishte Marsh to be protected as a Natural Monument under Macedonian law.Spirovska, M., et al. (2012) Blato-13_02_2012%20%20lektorirano-final.pdf Integrated Study on the State of the Remains of Studenchishte Marsh and Measures for its Revitalization, Dekons-Ema Drustvo za ekoloshki consulting. (Macedonian language)
Changes to the General Urban Plan for Ohrid 2014–2020, however, made provisions for Studenchishte Marsh to be drained and replaced with infrastructure for tourism and water-sports, a proposal which, together with other regional developments, was opposed by numerous local and international experts, including the Society of Wetland Scientists.Society of Wetland Scientists (2015) Letter to Mr Nikola Bakračeski, Mayor of the City of Ohrid . A Strategic Environmental Assessment also concluded that no measure except non-implementation could reduce the direct negative impact on Studenchishte and the indirect negative impact on Lake Ohrid if the proposed construction was to take place at the wetland.Dr. Borka Kovachevic (2015) Draft Report on the Strategic Environmental Assessment for Changes and Additions to the General Urban Plan for Ohrid. Plans to drain the area have subsequently been reversed and the Macedonian government announced in 2018 that it would move forward with proclamation of Studenchishte Marsh as a protected area and its designation together with Lake Ohrid as a Wetland of International Importance under the Ramsar Convention. Ramsar status was formalized in 2021 although protection of Studenchishte Marsh at the national level has not yet been completed.
The IUCN identifies wetland rehabilitation as one of five potential site needs for the UNESCO Natural and Cultural Heritage of the Ohrid Region.International Union for the Conservation of Nature (IUCN) (2017) Natural and Cultural Heritage of the Ohrid region 2017 Conservation Outlook Assessment , Gland, Switzerland. However, the potential to restore Struga Marsh, which was not included in the boundaries of the Ramsar Site, is likely to be reduced by construction of the European Corridor VIII railway, while Studenchishte's future is yet to be fully resolved.World Heritage Centre, ICOMOS and IUCN (2017) Reactive Monitoring Mission Report Natural and Cultural Heritage of the Ohrid Region (Former Yugoslav Republic of Macedonia), World Heritage Centre, Paris, France.
Fauna