In the searing heat of northern Iraq, among its dry, scrubby landscape, there's a surreal sight: a wide, shimmering blue lake, held back by the concrete and steel of a dam. It's on the Tigris River, near the city of Mosul.
Brig. Gen. Mohammad Ali Mughdeed, the commander of the soldiers guarding this dam, says even a small attack on the dam could have major repercussions: flooding, power cuts.
Right now, fighters from the Sunni militants now calling themselves the Islamic State are about six miles south, Mughdeed reckons and they've already tried to move on the dam more than once.
Islamist extremists have pushed Iraq into crisis. They have taken towns and cities, roads and bridges, and Iraq's army can't seem to push them back.
Now the militants and the army are battling for control of the two great rivers that flow through Iraq: the Tigris and the Euphrates. The extremists are believed to have skilled water engineers among their number, and if they control Iraq's waterways, they could create serious disasters.
A Precious, Imperiled Dam
In a country as arid as Iraq, the rivers are precious and beloved. Mughdeed walks down to the lake to wash his face, while the soldiers he commands skim stones.
These are Peshmerga soldiers, from Iraq's semi-autonomous Kurdish area. They are posted now on a military base close by, which was abandoned by the national Iraqi army soldiers as Mosul fell to extremists nearly two months ago.
Up at that base, the brigadier general explains why the dam he guards is so important.
If the dam is damaged, he thinks it would flood not just Mosul and the plains around it, but also affect the cities downriver Tikrit, Beiji, even maybe Baghdad.
He says if the militants capture the dam, they could threaten their enemies with flooding for example, if the Iraqi army made gains in Mosul. And it's a hydroelectric dam they could cut off the power. The commander believes the extremists know how to do it
When the Iraqi army was disbanded in 2003, there were military and technical experts who were left jobless. Mughdeed thinks they're now fighting with the Islamic State.
There's other evidence of skilled water engineers among the militants. When the Islamic State took Mosul, they systematically cut off water supply to enemy areas. Then they issued a series of pictures of their men fixing water systems damaged in the fighting.
Floods, Pollution And Shortages
Water has already been used as a weapon in this conflict. In the nearby city of Erbil, Colin MacInnes, UNICEF's deputy director in Iraq, points on a map to the Abu Ghraib area, where the Islamic State emptied a series of irrigation channels in May.
"This is just west of Baghdad," MacInnes says, "and this happened earlier on in the crisis where the communities of Ramadi and Fallujah become points of conflict."
By emptying those channels, the militants displaced 12,000 families, submerging hundreds of houses and at least four schools.
"It's an agricultural area and so all the agricultural lands were flooded and the crops were destroyed," MacInnes says. "The water sources themselves, within the community, became polluted, and so you no longer had clean water in the community."
In areas where water has been cut off, MacInnes says children have been badly affected cases of diarrhea and dehydration are on the rise.
And as the militants push toward Baghdad, there's been fierce fighting around two dams that are crucial for the capital's water supply: at Haditha, west of Baghdad, and the Hamrin lake to the north. Damage to either dam could create similar problems in the capital but on a much larger scale.
In Mosul, Brig.-Gen. Mughdeed knows what's at stake.
He says none of his men sleep at night, because they know how much the Islamic State wants the dam.