They are from different generations, different countries, and live 1,100km apart. Yet the fates of Suleyman Agalday and Nashwa Nasr are intertwined by policies transforming the Tigris River that has irrigated their societies for centuries. Today, both are threatened with displacement. In south-east Turkey, Mr Agalday, 39, will see the ancient caves and rock formations of his hometown, Hasankeyf, flooded as the waters slowly rise because of his government’s controversial Ilisu dam. Engineers are due to start filling the reservoir this month.

In the months ahead, homes, gardens and thousands of years of history will be submerged.  But the flooding of Mr Agalday’s home also threatens critical shortages for Ms Nasr’s southern Iraqi marshlands, which have long received the waters of Mesopotamia’s two great rivers, the Tigris and Euphrates, as they flowed down from the Turkish highlands. Like her ancestors, Ms Nasr raises water buffalo among the towering reeds. As a child, the waters were so high, she could lean out of her thatched house and scoop up water to drink. Now, even if the leathered 78-year-old could reach the water from her hut, it is too polluted to drink. Every day, she and her family agonise over whether to leave their home behind. “Everyone talks about migration, but where to?” she says. “All we know is raising buffalo. How would we survive? We’re looking for mercy from God. Here, water is mercy — and there is less and less of it.”