Lake İznik

Iznik Lake, located within the boundaries of Bursa province in the southeastern part of the Marmara Region, is Türkiye’s fifth largest and the Marmara Region’s largest natural lake. Covering an area of 298 km², this tectonic lake lies 85 metres above sea level. Known in antiquity as “Askania,” the lake lies between the districts of Iznik and Orhangazi and possesses freshwater. Its depth increases from north to south, reaching a maximum of 65 metres at its deepest point. Fishing activities in the lake target species such as carp, sea bass, yellow common bream and silver pike like.

Iznik Lake contains a basilica bearing traces of the Christian era and the Roman Empire, identified as historical. This discovery was made in 2014 during historical and cultural heritage surveys conducted by the Bursa Metropolitan Municipality. This underwater archaeological find, dated to the 4th–5th centuries CE, represents a important discovery. The district of Iznik, surrounding the lake, also attracts tourists with its historic structures and ancient ruins.

Map Representation

Geography and Climate

Iznik Lake lies between the district of Iznik to the east and the Gemlik Gulf to the west. It is surrounded by the Samanlı Mountains to the north and the Avdan Mountain to the south. The lake stretches approximately 32 km in a northwest–southeast direction and reaches a maximum width of 11.5 km. Situated within a tectonic basin shaped by the surrounding lowland ridges, the lake’s catchment area spans 1,246 km². The lake’s surroundings are covered by agricultural fields and olive groves. The main rivers feeding the catchment area are known as Karadere and Sölöz Creek. The lake is replenished by karstic springs and rain waters.

The area around Iznik Lake is one of Bursa Province’s key agricultural zones. Olive groves and vineyards constitute the primary agricultural activities in this region. Irrigation projects drawing water from the lake and fisheries are fundamental components of the local economy. Iznik Lake is also a natural attraction for tourists, with picnic areas and social facilities located around its shores. Camping tourism and day-use recreation areas around the lake enhance the region’s tourist appeal.

Biodiversity and Ecosystem

Iznik Lake possesses rich biodiversity. The lake is particularly significant as a habitat for birds, including several threatened species. For instance, birds such as the purple heron (Ardea purpurea), little bittern (Ardeola ralloides) and small pygmy cormorant (Phalacrocorax pygmeus) form substantial populations during their breeding season. Additionally, the oak forests and reed beds surrounding the lake hold considerable ecosystem value importance.

The lake’s water was once used for drinking and currently contributes economically through fisheries. Various ecosystem management initiatives are needed to protect the lake’s waterfowl and plant vegetation. However, threats such as irrigation projects and illegal water extraction endanger this biodiversity.

Iznik Lake (Source: Bursa Culture Portal)

Conservation Efforts and Threats

Iznik Lake was designated as a Seating Area in 1990. Although various efforts are underway to preserve the lake’s biodiversity, threats such as irrigation projects, pollution, and illegal fishing persist. Moreover, extralimital water extraction and the impact of environment settlements constitute significant threats. Therefore, increased awareness and conservation initiatives are required to safeguard the ecosystems surrounding the lake.