Complex sentence: The claims over rights to water in the Middle East are centred around the area's three major river systems-the Nile, the River Jordan, and the Tigris-Euphrates river basin.
Split into simpler sentences: The claims over rights to water in the Middle East are centred around the area's three major river systems. As mentioned above, these are the River Nile, the River Jordan, and the Tigris-Euphrates river basin.