Aerial photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Aerial photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Aerial photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Tourists glide above the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province, May 19, 2019. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Aerial photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)

　　Aerial photo taken on May 20, 2019 shows the scenery of the three gorges of the Yellow River in Yongjing County, northwest China's Gansu Province. The three gorges that consist of Bingling Gorge, Liujia Gorge and Yanguo Gorge are located at the upper reaches of the Yellow River, China's second largest river. (Xinhua/Fan Peishen)