Sometimes the Qizil Üzan and the Sefīd-Rūd are considered as one river, and the words Qizil Üzan and Sefīd-Rūd are used synonymously for the entire river that flows from the Zagros Mountains in Kordestan Province to the Caspian Sea. That definition's full river length is approximately , making it Iran's second longest river after the Karun.