Jhelum or Jehlam (both: jāˈləm) [key], westernmost of the five rivers of the Punjab, 480 mi (772 km) long. Rising in Jammu and Kashmir, India, it flows W through the Vale of Kashmir, S through Pakistan-occupied foothills, then SW across Punjab to the Chenab River. The Lower Jhelum Canal (opened 1901) and the Upper Jhelum Canal (1915) irrigate extensive areas of Pakistani Punjab. The Mangla Dam and Reservoir (1960) has greatly improved irrigation along the river's lower course, as well as supplying extensive hydroelectric power. The Jhelum was crossed in 326 B.C. by Alexander the Great, who defeated the Indian king Porus. The river's ancient name was Hydaspes.