People perform during a ceremony to offer sacrifices to water at the Dujiang Dam, an ancient but still operating irrigation project, in Southwest China's Sichuan province, April 5, 2015, the day of Chinese traditional Qingming Festival. The world's oldest irrigation project was built in 256 BC by local governor Li Bing during the Warring States (475-221 BC). The ceremony is held every year at the Qingming Festival to pray for favorable weather and commemorate the contributions made by Li Bing. [Photo/Xinhua]