Aerial photo taken on April 1, 2020 shows a helium balloon floating in the sky above the Xixi National Wetland Park in Hangzhou, east China's Zhejiang Province. (Xinhua/Weng Xinyang)

Photo taken on April 1, 2020 shows the scenery of flowers in the Xixi National Wetland Park in Hangzhou, east China's Zhejiang Province. (Xinhua/Weng Xinyang)

Aerial photo taken on April 1, 2020 shows the scenery of the Xixi National Wetland Park in Hangzhou, east China's Zhejiang Province. (Xinhua/Weng Xinyang)

Aerial photo taken on April 1, 2020 shows a boat sailing in the Xixi National Wetland Park in Hangzhou, east China's Zhejiang Province. (Xinhua/Weng Xinyang)

Aerial photo taken on April 1, 2020 shows a boat sailing in the Xixi National Wetland Park in Hangzhou, east China's Zhejiang Province. (Xinhua/Weng Xinyang)

Aerial photo taken on April 1, 2020 shows a boat sailing in the Xixi National Wetland Park in Hangzhou, east China's Zhejiang Province. (Xinhua/Weng Xinyang)