It is a fresh water lake located in the eastern half of a long pit joining the Adapazarı Plain to the Izmit Gulf groove in the eastern part of the Marmara Region.
The shores of Sapanca remain in the province of Sakarya in the east and Kocaeli in the west end. Its basin is 252 km2. Its area is 47 km2. East-west length is 17 km. The north-south width is 5 km and the height of the surface from the sea is 31 m. Its deepest place is 61 m.
The lake takes its name from the district established on the south coast. It is referred to as Ayan Lake in old Turkish sources. Especially well fed by the floods descending from the mountains to the south, the lake empties its excess water into the Sakarya river via the Çark water from its eastern end. The streams that feed the lake are Karaçay, Kuruçay, Kurtköy, Mahmudiye, Istanbul, Karadere and Kaymakçı. Partridge, woodcock and rabbit hunting are done on the mountain skirts extending in the north and south. All kinds of freshwater fish fishing is done in the lake.
Evliya Çelebi explains Sapanca as follows: “The surroundings of Sapanca Lake are 24 miles. There are seventy-six villages around the four towns. The colors of their faces are red since the people of the sentence drink from the water of this estuary.
Although the products are many, they have no ties. Its gardens are very transcendent. There is a kind of melon and watermelon on the edge of this lake, which can only attract two of them. There are eighty pare boats and hooves (grain boats) in this lake, where they take men, timber and belongings from the village. They hunt from seventy, eighty kinds of fish in this lake and make a profit. Freshwater fish such as trout, carp, pike are very tasty. The depth of the lake is twenty strokes in most places. Its water is very pure and clear. Women of the villages on the coast never rub soap when they wash clothes. The Sakarya River passes two hours from the east of this lake. It pours into the Black Sea on the edge of the town of İrva in Kocaeli. Sakarya can be poured into this lake with a little help. Since this lake is close to Izmit Bay for about three hours, its foot blends into the sea in front of Izmit Tuzla. Even in a century, although hundreds of thousands of digging and anchor capstans were collected to add this lake to Izmit Bay, the people of Izmit loosened it because it required many treasures and Noah’s life and prevented the completion of the work. But if the Sakarya River is mixed in this lake and in this lake in the Gulf of Izmit, it will be a five-mansion place until Bolu. The Istanbul Ships catch up in Bolu, and a board in Istanbul will have three coins, a weighbridge and five coins, and the marvel would be great. ”
According to the measurements by the Electrical Works Survey Department, the water of the lake rises in the winter and spring, lowers towards autumn. There is a difference of 70-90 cm, sometimes 120-130 cm between the two levels.
The E-5 Highway passes the northern shore of the lake, the TEM Highway and the railway cross the south.
Sapanca Lake, which is the result of tectonic formations in Sakarya and its surroundings, is a center that is open to recreation and accommodation demands, especially in Istanbul, due to its extremely striking natural beauties and its location in a location accessible by dense settlements. . There are beautiful camping and picnic areas in the Arifiye Forest at the heights of Lake Sapanca.
Sapanca Lake, where national and international surfing, sailing and rowing competitions are held, attracts many visitors for sporting purposes.