The Lingqu Canal, also known as Qin Zaoqu or Duh River, is located in Xing'an County, Guilin City. It can be directly reached by National Highway 322, and it is 60 kilometers away from the center of Guilin City. Completed in the 33rd year of Emperor Qin Shi Huang's reign (214 BC), it is regarded as one of the three great water conservancy projects of the Qin Dynasty, alongside the Dujiangyan Irrigation System in Sichuan and the Zhengguo Canal in Shaanxi. It is one of the oldest canals in the world. It has a history of over 2200 years and has played an extremely important role in the economic and cultural exchange between the Central Plains and the Lingnan region. It has made indelible contributions to maintaining national unity and consolidating border defense.
In 221 BC, after Emperor Qin Shi Huang unified the six states, in order to complete the great cause of unifying China, he then "sent General Tu Wei to lead the naval forces southward to attack the Baiyue people" and advanced into the Lingnan region. The Qin army of 550,000 troops was divided into five routes to advance towards the Baiyue region. One of the Qin armies advancing into Guangxi encountered fierce resistance from local tribes, forcing the Qin army to remain armed for "three years without taking off armor or relaxing bows" (from Huainanzi: Renjianxun). Investigating the reasons for the military setbacks, they were related to the Qin army's inability to adapt to mountain warfare, their intolerance to southern soil and climate, and the high number of sick soldiers. However, more importantly, the rugged terrain of the Lingnan region, the long transportation lines, and the inability to supply military provisions were critical issues. Solving the problem of transporting military provisions became the key to deciding the victory or defeat of this war. Emperor Qin Shi Huang decisively made the decision to "have Jian Lu dig a canal to transport grain" (from Records of the Grand Historian: Biography of Lord Pingjin Hou).
Under the supervision of Shi Lu, with the hard work of the laborers who were conscripted and the Qin army, after several cold and hot seasons, the Lingqu Canal was successfully dug. The Qin army's supplies were transported by ship from the Xiang River, through the Lingqu Canal into the Li River, and continuously delivered to the front line, ensuring the needs of the front-line military. In the 33rd year of Emperor Qin Shi Huang's reign, the Qin army finally unified the Lingnan region, established the commanderies of Guilin, Nanhai, and Xiang, and stationed troops there. Thus, Emperor Qin Shi Huang completed his great achievement of unifying the whole country.
The technology used in digging the Lingqu Canal achieved brilliant accomplishments in the history of ancient hydraulic engineering and still shines brightly today. Xing'an County is located in the northern mountainous area of Guangxi, surrounded by towering mountains and crisscrossing rivers. To the southeast stands one of the Five Ridges, the Dupo Ridge, while to the south are the continuous Haiyang Mountains. To the northwest lies the majestic Yuecheng Ridge. The prominent geographical feature is that the southeastern part is higher in the south and lower in the north, while the northwestern part is higher in the north and lower in the south. In the middle of Xing'an County, there is a lowland area with an altitude of only about 200 meters, which is the famous Xiang-Gui Corridor, historically an important traffic route from Hunan to Guangxi. Due to this geographical feature, the Xiang River, originating from Haiyang Mountain, flows northward to Xing'an County, following the Xiang-Gui Corridor through Quanzhou County and enters Hunan's Dongting Lake; the Li River, originating from the main peak of the Yuecheng Ridge, Mao'er Mountain, flows southward to Rongjiang, passes through Lingchuan County and Guilin City, and converges into the West River at Wuzhou, eventually flowing into the Pearl River in Guangdong. The Xiang River flows northward, while the Li River flows southward, hence the saying: "Xing'an is ten thousand feet high, water flows in two directions." The Xiang River and the Li River are within 25 kilometers of each other in Xing'an County. Directly digging a canal to connect the two rivers during the Qin Dynasty would have been quite difficult. Fortunately, the Li River has a tributary called the Ling River, formed by the confluence of many small streams, among which one is named Shian Water. Shian Water originates from Fugui Ridge near Xing'an, with a straight-line distance of only 2.5 kilometers from the Xiang River. However, it is separated by a ridge that is more than 300 meters wide and about 30 meters high, known as Yuecheng Ridge (also called Shian Ridge or Linyuan Ridge), which is the watershed between the Xiang and Li Rivers. As long as this ridge is penetrated, the Xiang River water at a higher altitude can be introduced into the Shian Water, thereby connecting the Li River. After careful surveying, the smart designer of the time discovered this secret. Therefore, the Qin army built a dam across the Xiang River, raising the water level, dug a 5-kilometer-long channel, and excavated Taishi Temple Mountain on Yuecheng Ridge, introducing the Xiang River water into the Shian Water. They also improved and redirected the Shian Water so that ships could pass through it into the Ling River, entering the Li River, thus connecting the Xiang and Li Rivers. According to historical records from the Tang Dynasty, apart from the channel, the Lingqu Canal already had structures such as large and small Tianping (also known as Huadi), Hamouth, Qin Dyke, flood discharge Tianping, and sluice gates, which are basically the same as what we see today in the Lingqu Canal. These scientifically designed and closely connected structures make the Lingqu Canal an immortal hydraulic engineering project.