Aerial photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)

Aerial photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)

Aerial photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)

Photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)

Tourists visit the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province, Sept. 5, 2018. (Xinhua/Tao Ming)

Aerial photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)

Tourists visit the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province, Sept. 5, 2018. (Xinhua/Tao Ming)

Aerial photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)

Aerial photo taken on Sept. 5, 2018 shows a view of the Zhangye National Wetland Park in the Ganzhou District of Zhangye, northwest China's Gansu Province. (Xinhua/Tao Ming)