The Hukou Waterfall, is the largest waterfall on the Yellow River, the second largest waterfall in China (after the Huangguoshu Waterfall in Guizhou), and the world's largest yellow waterfall. 

It is located at the intersection of the provinces of Shanxi and Shaanxi, 165 km (103 mi) to the west of Fenxi County, and 50 km (31 mi) to the east of Yichuan County where the middle reaches of the Yellow River flow through Jinxia Grand Canyon. 

The width of the waterfall changes with the season, usually 30 metres (98 ft) wide but increasing to 50 m (164 ft) during flood season. It has a height of over 20 m (66 ft). When the Yellow River approaches the Hukou Mountain, blocked by mountains on both sides, its width is abruptly narrowed down to 20–30 m (66–98 ft). 

The water's velocity increases, and then plunges over a narrow opening on a cliff, forming a waterfall 15 m (49 ft) high and 20 m (66 ft) wide, as if water were pouring down from a huge teapot. Hence it gets the name Hukou (literally, "flask mouth") Waterfall.

According to en.wikipedia