On this day, 33 years ago, on October 20, 1992 (September 25, 1992, the lunar calendar), Gansu built the world's longest water diversion tunnel. In October 1992, the world's longest water diversion tunnel, the Pandaoling Tunnel in Gansu Province, passed the acceptance of relevant departments. The Gansu Water Diversion Project from Da (Tonghe) to Qin (Wangchuan) is the largest gravity irrigation water conservancy project in northwest China. With a total length of 15.72 kilometers, the Pandaoling Tunnel is the longest tunnel in this project and one of the 10 large tunnels in the world, including railways, highways and other tunnels.