The Beas River  runs through the Northwestern Indian states of Himachal Pradesh and Punjab. The river was also known as Arjiki or Vipas to the ancient Indians and the Hyphasis to the Ancient Greeks. The Beas River marks the eastern-most border of Alexander the Great's conquests in 326 BC. The river begins at the Rohtang Pass in the state of Himachal Pradesh, and merges with the Sutlej in Punjab, India. The Sutlej continues into Pakistani Punjab and joins the Chenab River to form the Panjab the latter joins the Indus River at Mithankot. The waters of the Beas and Sutlej rivers are allocated to India under the Indus Waters Treaty between India and Pakistan.