Lake Urmia is a hypersaline lake in northwestern Iran, once the largest lake in the Middle East and sixth largest saltwater lake in the world. Since the 1970s it has lost over 80 percent of its surface area due to dam construction on its tributaries, intensive agriculture, and drought. Its collapse has triggered dust storms and soil salinisation across the region.

The Lake Urmia basin has been settled since antiquity. The lake, referred to in ancient Assyrian texts and by classical geographers, was a landmark on the routes between Mesopotamia and the Iranian plateau. The region’s mixed ecology of lake, wetland, and mountain supported a diverse population and productive agriculture fed by rivers flowing from the surrounding mountains. In the early twentieth century the basin attracted Western missionaries who established schools and hospitals serving Assyrian, Armenian, and Kurdish communities around the lake’s shores.

Lake Urmia itself has lost over 80 percent of its surface area since the 1970s, shrinking from approximately 5,200 square kilometres to under 1,000. The primary causes are dam construction on the eleven rivers feeding the lake, which has reduced inflows by over 40 percent, and intensive irrigation that extracts water before it reaches the lake. The exposed lake bed is a source of toxic salt and dust affecting millions of people in the northwest. The Iranian government has launched restoration programmes including water transfers and agricultural water restrictions, with limited success.