2018 looks to be one of the worst years in decades for Iraq’s chronically mismanaged water sector, fueling major protests. The filling of Turkey’s Ilisu reservoir starting this month will only worsen the situation.

Iraq has weathered immense challenges in recent years — foremost among them the Islamic State (IS) insurgency which at one point occupied about one-third of the country and threatened security nationwide. Yet as the smoke clears, Iraqis find themselves...