Tortum Waterfall does not always fall. A hydroelectric plant built into the gorge between 1952 and 1960 draws the Tortum Stream into a channel above the lip and sends it down to its turbines, so for much of the year the 48-metre drop carries only the water the plant is legally obliged to let through. The older half of the story is geological. Roughly three centuries ago a limestone flank of Kemerli Mountain broke away and slid into the valley, damming the stream and drowning eight kilometres of it beneath what is now Lake Tortum. The waterfall is simply where that lake escapes: the overflow crosses the landslide barrier, reaches a lip of hard limestone about twenty metres wide, and drops in one sheet into a pool it has drilled for itself. A mountain built this waterfall, and an engineer now decides when it runs.
When it runs, it runs hard. May and June are the loud months: snowmelt fills the lake faster than the plant can take it, the water goes over the brink at full width, and you hear it from the road before you see it. Stone stairs and an iron railing drop from the rim to the pool at the foot, and by the last step the spray has soaked your sleeves. In the afternoon the sun swings round to face the mist and a rainbow stands inside the cloud. The slopes around the gorge are bare and pale, so the green cleft and its waterfall come into view with no warning at all. Today the falls reach full strength only while the snow is melting. For the rest of the year what crosses the lip is the minimum release the courts have obliged the plant to leave, and by a dry September that can be a thin ribbon down a wide grey wall.