Moeris (mēr`ĭs), ancient name of Lake Karun (Arab. Birket Qarun), c.90 sq mi (230 sq km), NE Egypt, in El Faiyum. The size of the lake is much reduced from that described by ancient travelers, such as Herodotus. Crocodilopolis (later Arsinoë) was the chief town on the lake and a residence of the Ptolemies. Ancient irrigation works were excavated in the late 1920s. By the late 20th cent. the lake, shallow and salty, measured 24 by 5 mi (40 by 8 km) and was c.40 ft (12 m) below sea level. As a result, Lake Karun is fed by a canal from the Nile River.