Zheng Guo Canal: From a strategy to exhaust Qin to a strategy to strengthen Qin

Zheng Guo Canal, located on the north bank of Jing River, 25 kilometers northwest of Jingyang County, Shaanxi Province, was built under the supervision of Zheng Guo, a water conservancy expert from Han, in 246 BC (the first year of King Zheng of Qin). It is one of the earliest large-scale water conservancy projects built on the Guanzhong Plain. In the late Warring States period, among the seven feudal states of Qin, Qi, Chu, Yan, Zhao, Wei, and Han, Qin was growing rapidly and was eyeing the other six states. Han, located on the key route for Qin to exit Hangu Pass and advance into the Central Plains, could be swallowed by Qin at any time. In 246 BC, King Huan of Han, in a state of constant fear and desperation, adopted a very crude so-called 'exhausting Qin' strategy: he sent the famous water engineer Zheng Guo to Qin to persuade Qin to dig a large irrigation canal between Jing River and Luo River (both tributaries of Wei River). On the surface, it was to develop Qin's agriculture, but the real purpose was to exhaust Qin's strength, delay Qin's eastward advance, and gain a respite. After Zheng Guo arrived in Qin, he persuaded King Qin to dig a canal, diverting Jing River to Luo River, and irrigating the land along the river. Ying Zheng, who had just ascended the throne, wanted to develop water conservancy and accumulate strength to prepare for the unification of the six states. So, he quickly accepted this attractive suggestion and immediately recruited more than 100,000 workers and a large amount of materials, appointed Zheng Guo to supervise the construction, and launched the most magnificent and spectacular water conservancy project at that time. During the construction process, Han's 'exhausting Qin' plot was exposed, and King Qin was furious and wanted to kill Zheng Guo. Zheng Guo defended himself by saying: 'At first, I was a spy, but when the canal is completed, it will also benefit Qin. I delayed Han's life for a few years, but I have made a great contribution to Qin for thousands of generations.' Ying Zheng was a far-sighted politician. He thought Zheng Guo made sense, and the project also needed Zheng Guo. After weighing the pros and cons, he decided to continue to use Zheng Guo and let him be responsible for the project to the end. The project took ten years to complete and was named Zheng Guo Canal. The Zheng Guo Canal project took advantage of the high northwest and low southeast terrain, built a stone dam on the Jing River in the northwest of Jingyang County, intercepted the river water, raised the water level, and introduced it into the main canal. The main canal was arranged at the highest point of the irrigation canal, extending eastward along the foot of the north mountain, passing through Jingyang, Sanyuan, Fuping, Pucheng and other counties, and finally flowing into Luo River south of Jincheng Village, Pucheng County. Along the way, it cut off the rivers along the mountain, incorporated the smelting water, clear water, turbid water, and Shichuan water into the canal to increase the water volume. In an area of 300 li, Zheng Guo Canal formed a dense irrigation system like a spider web between the three rivers of Jing, Luo, and Wei in the northern part of the Guanzhong Plain. The completion of Zheng Guo Canal allowed the scarce rainfall and poor land of Guanzhong to be irrigated, greatly improving the agricultural production in Guanzhong. The Guanzhong Plain gradually became the granary of Qin. Six years after the completion of Zheng Guo Canal, Qin destroyed Han, and Han, who had thrown out the 'exhausting Qin' strategy, was wiped out. Fifteen years after the completion of Zheng Guo Canal, Qin destroyed the six states and achieved unification of the world.