Ships pass the navigation lock of the Three Gorges in Yichang, central China's Hubei Province, May 30, 2015. The freight getting through the navigation lock of the Three Gorges has topped 34.28 million tons from January to April this year, up 5.77 percent compared with that of last year. (Xinhua/Wang Jiaman)

Ships pass the navigation lock of the Three Gorges in Yichang, central China's Hubei Province, May 30, 2015. The freight getting through the navigation lock of the Three Gorges has topped 34.28 million tons from January to April this year, up 5.77 percent compared with that of last year. (Xinhua/Zheng Jiayu)

Ships pass the navigation lock of the Three Gorges in Yichang, central China's Hubei Province, May 30, 2015. The freight getting through the navigation lock of the Three Gorges has topped 34.28 million tons from January to April this year, up 5.77 percent compared with that of last year. (Xinhua/Wang Jiaman)

Ships sail on the lower reaches of the navigation lock of the Three Gorges in Yichang, central China's Hubei Province, May 30, 2015. The freight getting through the navigation lock of the Three Gorges has topped 34.28 million tons from January to April this year, up 5.77 percent compared with that of last year. (Xinhua/Zheng Jiayu)