Aerial photo taken on Aug. 16, 2020 shows the Tuotuo River, a source of the Yangtze River, in northwest China's Qinghai Province. (Photo: Xinhua/Wu Gang)

Aerial photo taken on Aug. 14, 2020 shows a section of the Dangqu River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 16, 2020 shows a section of the Tuotuo River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 14, 2020 shows a section of the Dangqu River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 16, 2020 shows the Tuotuo River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 16, 2020 shows the Tuotuo River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 14, 2020 shows a section of the Dangqu River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 16, 2020 shows the Tuotuo River, a source of the Yangtze River, in northwest China's Qinghai Province.

Aerial photo taken on Aug. 14, 2020 shows a section of the Dangqu River, a source of the Yangtze River, in northwest China's Qinghai Province.