Complex sentence: The Euphrates has often terminated near Nasiriyah into the Hammar Marshes as its flow slows and the Tigris can distribute some of its flow into the Central and Hawizeh marshes as it slows near Amarah.
Split into simpler sentences: The Euphrates has often terminated near Nasiriyah into the Hammar Marshes as its flow slows. The Tigris can distribute some of its flow into the Central and Hawizeh marshes as it slows near Amarah.