The dam, the river and the spring that fed ancient Side

Guests from Side usually ask the same question on deck: is this lake natural? The answer connects the canyon to the town you are staying in, and it is a better story than any brochure tells.

A river, then a wall

The Manavgat river rises in the Taurus and runs 93 km to the sea, passing the town of Manavgat and its waterfall on the way. In the mountains above the town it cut a deep, narrow gorge. In 1984 the Oymapınar dam closed that gorge: a wall 185 metres high, built to make electricity.

How a gorge became a lake

Behind the dam the water rose and filled the gorge to the brim, about 300 million cubic metres of it. The cliffs that once stood over a river now drop straight into a lake. That is why the shoreline is so steep and the bays so sheltered — and why the catamarans can cruise for hours between walls of pine.

The spring under the lake

Before the dam, one of the most powerful karst springs of the region surfaced in this valley: Dumanlı. In antiquity its water was carried to Side, and the remains of that aqueduct still stand on the way into the old town. When the reservoir filled, the spring disappeared under roughly 120 metres of water. It still flows — you just cannot see it.

Why the water is green

The colour comes from the limestone. Water filtered through the karst carries fine dissolved minerals and very little sediment, so the light that reaches the depth comes back emerald. On a sunny day the effect is strongest in the narrow sections, where the walls cut the glare.