The Ceyhan River (historically Pyramos or Pyramus (Greek: Πύραμος), Leucosyrus or Jihun) is a river in Anatolia in the south of Turkey.
The Ceyhan River (Pyramus) has its source (known as Söğütlü Dere) at a location called Pınarbaşı 3 km (1.9 mi) on the Nurhak Mountains of the Eastern Taurus Mountains range, southeast of the town of Elbistan in the Kahramanmaraş province of Turkey . According to classical references its source is at Cataonia near the town of Arabissus. Its main tributaries are called Harman, Göksun, Mağara Gözü, Fırnız, Tekir, Körsulu, Aksu (which joins Ceyhan at on the outskirts of Kahramanmaraş), Çakur, Susas, Çeperce. Its total length is 509 km or 316 miles.
In classical times for a time it passed under ground, but then came forward again as a navigable river, and forced its way through a glen of Mount Taurus, which in some parts was so narrow that Strabo claims a dog or hare could leap across it. Its course, which to this point had been south, then turned to the southwest, and reached the sea. The river was deep and rapid; its average breadth was 1 stadium.
At present, because of the narrow deep valleys that used to exist, the Ceyhan River has been dammed for hydroelectric generation, for flood control and for providing irrigation to the fertile Cukurova region. The main hydroelectric generating dams are at Menzelet, Kılavuzlu, Aslantaş, Sır and Berke. Of the deep valleys, only the one called Kisikli Canyon exists in its natural form, south of the location the Menzelet Dam.
The quantity of water flow on the Ceyhan River changes greatly season by season. During August and September the river is at its lowest flow. During November and December the autumn rains temporarily raise the water flow rate (from 50 cubic metres (1,800 cu ft) per sec to 380 cubic metres (13,000 cu ft) per sec). In January the flow rate decreases until mid-February. As the snows melt in the Taurus Mountains during spring and early summer months, the flow increases and, periodically caused flooding prior to its damming. During the last quarter of the 20th century, during the floods, the two rivers of the Cukurova plain, the Ceyhan River and the Seyhan River, joined together at least 6 times.