Tigris–Euphrates river system border. Since the 1960s and in the 1970s, when Turkey began the GAP project in earnest, water disputes have regularly occurred in addition to the associated dam's effects on the environment. In addition, Syrian and Iranian dam construction has also contributed to political tension within the basin, particularly during drought. The general climate of the region is subtropical, hot and arid. At the northern end of the Persian Gulf is the vast floodplain of the Euphrates, Tigris, and Karun Rivers, featuring huge permanent lakes, marshes, and forest. The aquatic vegetation includes reeds, rushes, and papyrus, which support numerous species. Areas
Karasu (Euphrates) through a rocky gorge. Near the small town of Kemaliye it receives its last tributary, the Çaltısuyu, before turning sharply southeast to flow through a deep canyon into the Keban Dam Lake on the Euphrates. Before construction of the Keban Dam the Karasu joined the Murat River 10 km above the dam site and 13 km above the town of Keban. In 1996, 15 Turkish soldiers were killed when their personnel carrier fell into the river during a routine crossing. When temperatures in Turkey dropped below -25 °C in 2005 the river froze over and was used as a football