There are different opinions about the legend of the upstream river. One mountain apart, east of Riyueshan, the Han people have said for thousands of years that in order to communicate the relationship between the Tibetan and Han nationalities and promote cultural exchanges, Tang Wang Li Shimin married the young and beautiful Wencheng princess to Tubo Songzan Ganbu. On her way to Tibet, Princess Wencheng did not look back at Chang'an and looked desolately to the west. She missed her hometown, missed her parents, was sad and moved westward. The princess's tears merged into this upside-down river. To the west of Riyueshan, another myth spread among the Tibetans - "The Dragon King sent his four sons and daughters to make the four rivers of East and west. When the youngest daughter made the West Sea, 108 rivers were needed. She found 107 rivers, and the last one was nowhere to be found. The smart and cunning dragon lady brought a river from Riyueshan Mountain, which is called an upside-down river. The third way of saying is that the river is an upside-down river of the Dragon King. The upside-down river originates from the Chahan grassland at the foot of the Shanxi Mountains of Riyueshan Mountain, about 3300 meters above sea level, about 40 kilometers in length, and flows from east to west into the Zaihu of Qinghai Lake, Erhai (commonly known as Xiaohu), so it is called an upside-down river. The Tibetan word "Roumoyong" means an enviable place. It is the smallest branch of the Qinghai Lake water system, not only the winding river, but also the clear river bottom. In fact, the upside-down river was also an east-flowing river. It was injected into the Yellow River with the Buha River and Luohantang River. Because of the crustal changes, the Riyueshan Mountains uplifted, and then it turned to the west to inject into Qinghai Lake, becoming an upside-down river.