Hamun-i-Helmand or Sistan Lake, marshy lake in the Sistan, c.5,000 sq mi (12,950 sq km), on the Iran-Afghanistan border. The lake, fed by the Helmand, Farah, and other rivers, varies in size during the year, achieving its maximum extent in the late spring, when it overflows via the Shelagh River (in Iran) into the Gaud-i-Zirreh, an area of salt flats and swamps in SW Afghanistan. The Hamun-i-Helmand has the potential to support irrigated agriculture in the area. The Helmand irrigation project in SW Iran has been undertaken to support irrigated agriculture.

See Hamun-e Helmand