This is one of the most spectacular waterfall images I've ever seen, and certainly the most evocative landscape you have ever made, Xin. I am so proud of you. It is the rainbow that makes it work -- you were very fortunate to be there at the precise moment when light conditions created it for you. But you did not stop there --your selective use of exposure is extremely evocative -- allowing the surrounding hills to become barely seen gates of gold was perfect. You also found a vantage point where you could frame the falls on a diagonal, increasing the tremendous thrust of its cascade. The trees on the bottom anchor the image, echoing the flow of the falls. You made the most of your light and your vantage point to make a truly expressive landscape. It speaks of the power and beauty of nature as it is seldom seen.
I shot the same waterfall, and will be posting two images of it in November. The both express similar ideas, but I did not have the quality of light to work with, or the gift of a magical rainbow, so I had to work with other aspects.
i salute you for this image, for recognizing what you had here, and make the very most of it, Xin.