Long lake is the highest, largest and deepest lake in Jiuzhaigou Valley, at 3100 meter above sea level.
The color of the water in the lake changes through the four seasons.
The source of the water in Long lake is the melting ice at the surrounding mountains. As the lake does not have an outlet linking it to any other lake or river, its water seeps out to lower valleys.
However the lake is never overfilled or drained dry at any time of the year. The Tibetan locals refer to it as the precious container that will not overflow and is never empty.