Aerial photo taken on April 3, 2021 shows the scenery of mountains in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers. (Photos: Xinhua/Feng Kaihua)

Aerial photo taken on April 5, 2021 shows the scenery of the Yellow River in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 3, 2021 shows the water mark of the Yellow River in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 5, 2021 shows the scenery of mountains in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 4, 2021 shows the scenery of mountains in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 4, 2021 shows the scenery of Nanchangtan Village in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 5, 2021 shows the scenery of the Yellow River in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 5, 2021 shows the scenery of Nanchangtan Village in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 5, 2021 shows the scenery of Nanchangtan Village in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 4, 2021 shows the scenery of the Yellow River in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.

Aerial photo taken on April 4, 2021 shows the scenery of Nanchangtan Village in the Heishan Gorge area in Zhongwei City, northwest China's Ningxia Hui Autonomous Region. Heishan Gorge is located in the upper reaches of the Yellow River, with a total length of over 70 kilometers.