A few thousand years ago, Lake Terkos was a small bay with a connection to the Black Sea. Over time, however, the barriers made by the waves from the sand caused this small bay to break away from the sea and turn into a freshwater lake. The main sources feeding Lake Terkos, also known as Durusu, are Bloody Creek, Basköy Creek, Çiftlikköy Creek, Belgrade Creek and Binkılıç Creek. The area is 25 square kilometers, the height of the sea is about 4 meters, the deepest part is 11 meters. Given the current situation, it stands out as the cleanest and best preserved of Istanbul’s three natural lakes. It also meets a significant part of Istanbul’s water needs.
Roe deer, wild boar, badger, squirrel, rock hoarse, scarves, jackals and foxes live in the forest surrounding Lake Terkos. Catfish, carp, freshwater perch and eel are common species. Around 200 bird species are seen in the lake. There are endangered bird species on a global scale, such as the bakery patka, the Siberian goose and the great forest eagle.
A 100-150 m long canal stretches between the lake and the Black Sea. Water from the Black Sea during very dry periods is poured into the lake after resting in this canal. The biggest threat is the illegal sand from the sea. The distance between the sea and the lake is getting shorter as the lake’s dunes are being carved by illegal sandboats. If necessary measures are not taken, the Black Sea will invade Lake Terkos.