THE Middle East is arid. But it is also home to some of the world’s most fertile rivers, such as the Nile. So it is all the more alarming that one of its great river basins, the Tigris-Euphrates—which flows through the so-called fertile crescent that gave birth to agriculture itself—is getting drier. According to a study in Water Resources Research, an American scientific journal, between 2003 and 2009 the region that stretches from eastern Turkey to western Iran lost 144 cubic kilometres of fresh water.