National Geographic: "Ethiopia is killing us," taxi driver Ahmed Hossam said, as he picked his way through Cairo's notoriously traffic-clogged streets. "If they build this dam, there will be no Nile. If there's no Nile, then there's no Egypt." Projects on the scale of the $4.7 billion, 1.1-mile-long (1.7-kilometer-long) Grand Ethiopian Renaissance Dam often encounter impassioned resistance, but few inspire the kind of dread and fury with which most Egyptians regard plans to dam the Blue Nile River. Egypt insists Ethiopia's...