Aerial photo taken on April 11, 2019 shows a view of the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province. The Qinghai Lake goes into a "frozen period" every mid-December and completely melts in mid-April next year. [Photo: Xinhua/Zhang Hongxiang]"

Aerial photo taken on April 11, 2019 shows a view of the Xiannvwan scenic spot of Qinghai Lake in northwest China's Qinghai Province. [Photo: Xinhua/Zhao Yuhe]"

A brown-headed gull flies over a lake at the Xiannvwan scenic spot of Qinghai Lake in northwest China's Qinghai Province, April 10, 2019. [Photo: Xinhua/Zhang Hongxiang]"

Aerial photo taken on April 11, 2019 shows a view of the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province. [Photo: Xinhua/Zhang Hongxiang]"

Aerial photo taken on April 11, 2019 shows a view of the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province. [Photo: Xinhua/Zhang Hongxiang]"

People pose for photos at the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province, April 11, 2019. [Photo: Xinhua/Zhang Hongxiang]"

Aerial photo taken on April 11, 2019 shows a view of the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province. [Photo: Xinhua/Zhang Hongxiang]"

Aerial photo taken on April 11, 2019 shows a view of the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province. [Photo: Xinhua/Zhang Hongxiang]"

Aerial photo taken on April 11, 2019 shows a view of the Erlangjian scenic spot of Qinghai Lake in northwest China's Qinghai Province. [Photo: Xinhua/Zhang Hongxiang]"

Brown-headed gulls rest at the Xiannvwan scenic spot of Qinghai Lake in northwest China's Qinghai Province, April 10, 2019. [Photo: Xinhua/Zhang Hongxiang]"