Photo taken on June 2, 2019 shows a yacht sailing in the Liujiaxia Reservoir in Yongjing County, northwest China's Gansu Province. A sharp contrast of colors is clearly shown when two rivers, silt-free Yellow River and its contributory Taohe River that flows with large amount of mud and sand meet in the Liujiaxia Reservoir which is widely-known for its clear water. (Xinhua/Ma Ning)