Tourists visit Hukou Waterfall on the Yellow River on Dec 27. They viewed a rainbow over the frozen Hukou Waterfall. [Photo by Lyu Guiming/China Daily]

Fast-flowing water sprays into the air, partially obscuring the view of Hukou Waterfall. On average, the water volume of Hukou Waterfall in winter is between 300 to 500 cubic meters per second. [Photo by Lyu Guiming/China Daily]