The Hawizeh Marshes are a complex of marshes that straddle the Iraq and Iran border. The marshes are fed by two branches of the Tigris River (the Al-Musharrah and Al-Kahla) in Iraq and Karkheh River in Iran. The Hawizeh marsh is critical to the survival of the Central and Hammar marshes, which also make up the Mesopotamian Marshes, because they are a refuge for species that may recolonize or reproduce into the other marshlands. The Hawizeh Marshes are drained by the Al-Kassarah.