The threat from the jihadists is so critical that U.S. forces are bombing the militants close to both the Mosul and Haditha dams — Iraq’s largest — on a near-daily basis. But the radical Islamists continue to menace both facilities.

The Sunni militants want to seize the dams to bolster their claim they are building an actual state; the dams are key to irrigating the country’s vast wheat fields and providing Iraqis with electricity. More ominously, the Islamic State has used its control over water facilities — including as many as four dams along the Tigris and Euphrates rivers — to displace communities or deprive them of crucial water supplies.

The Islamic State “understands how powerful water is as a tool, and they are not afraid to use it,” said Michael Stephens, a Middle East expert and deputy director of the Royal United Services Institute, a London-based security studies think tank.