Lake Copais, also spelled Kopais or Kopaida, was a lake in the centre of Boeotia, Greece, west of Thebes. It was drained in the late 19th century. The area where it was located, though now a plain, is still known as Kopaida. A one-time island in the lake was modified in ancient times into a megalithic citadel, now called Gla, though its ancient name is not known. It may be the city of Arne mentioned by Homer.
Drainage
When the lake existed, the towns of Haliartus, Orchomenus, and Chaeronea were on its shores. Rivers feeding the lake included the Cephissus, Termessus and Triton. The lake was surrounded by fertile land, but the lake increasingly encroached on the surrounding land because of inadequate drainage. In response to this, in 1867–1887 Scots and French engineers reclaimed the land for the British Lake Copais Company, by building channels to drain water from the lake to the Cephissus and from there to Lake Yliki. In total about were reclaimed. This land was returned to the Greek government in 1952. The Kopais Lake Agency was created in 1957 to supervise the draining of the lake and building of a new road. The task was completed that same year, but the agency with full-time staff of 30 still existed until 2010. Before this the lake drained into the sea by numerous subterranean channels. Some of these channels were artificial, as the 1st century geographer Straborecorded. Modern excavation has found enormous channels dug in the 14th century BCE which drained water into the sea to the northeast; Strabo mentions work being done on these channels by an engineer named Crates of Chalcis in the time of Alexander the Great.
and other ancient authors refer to Copais as the "Cephisian lake", named for the river Cephissus. Strabo, however, argues that the poetic expression refers to the smaller Lake Hylice, between Thebes and Anthedon. There was a legend that the lake came into being when the hero Heracles flooded the area by digging out a river, the Cephissus, which poured into the basin. Polyaenus explains that he did this because he was fighting the Minyans of Orchomenus: they were dangerous horseback fighters, and Heracles dug the lake in order to unhorse them. Another story has the lake overflow in the mythical time of Ogyges, resulting in the Ogygian deluge. The travel writerPausanias and the 5th century BCE comic playwright Aristophanes record that in antiquity Lake Copais was known for its fish, especially the eels.
