Located in the municipality of Castro Marim, the dam was built on the Odeleite stream, which rises in the Serra do Caldeirão and is a tributary of the Guadiana River.

In 2015, according to the Portugal de Norte a Sul blog, an aerial photograph showed that the dam's reservoir is shaped like a blue dragon. "This is an important symbol of power, strength and good luck in Chinese culture, as well as being a pattern traditionally used by emperors throughout history. That's why, in recent years, international attention has been drawn to the so-called 'River of the Blue Dragon', especially by Chinese tourists", they said.

According to Postal, the photo was taken by a traveller on a flight between Amsterdam and Marrakech, which flew over the Algarve. He shared the photo on Reddit and that was enough to spread the word.

The image went viral and reached Sina Weibo, a social network in China similar to Twitter. It then appeared on the Chinese television channel CCTV and spread across social media platforms around the world as the "River of the Blue Dragon", one of the most beautiful rivers in the world.