Guoqu Zheng

In the first 246 years (the first year of the King of Qin), the King of Qin adopted the advice of Zheng Guo, a Korean, and Zheng Guo presided over the construction of a large irrigation canal, which led water mirror water from the west to Luoshui in the east, with a total length of more than 300 miles. Jinghe River rushes out from the mountainous area of northern Shaanxi, flows to Liquan and enters the Guanzhong Plain. The plain is hundreds of miles from east to west and dozens of miles from north to south. The plain is slightly higher in the northwest and lower in the southeast. Zheng Guoqu made full use of this favorable terrain and began to build a main canal at Gukou in the northeast of Liquan County, so that the main canal extended eastward along the northern foot. Naturally, the main canal is located in the highest part of the irrigation area, which not only controls the irrigation area to the maximum extent, but also forms a full gravity irrigation system, which can irrigate more than 40 thousand hectares. Since the excavation in Zheng Guoqu, the head of the main canal has been gradually filled up due to sediment deposition, and water cannot enter the channel. Since the past dynasties, the place where the river enters the canal has been constantly changing at Gukou, but the channel of the main canal below Gukou remains unchanged.

Dujiangyan irrigation system

In the fifty-first year of the Qin Dynasty (256 BC), Li Bing and his son, the prefect of Shu County, absorbed the experience of predecessors in water control and led the local people to build the world-famous Dujiangyan water conservancy project. Dujiangyan's master plan is to divide the Minjiang River into two branches, one of which is introduced into Chengdu Plain, which can not only divert floods and reduce disasters, but also divert water to irrigate farmland and turn harm into benefit. The main works include Yuzui diversion dike, Sha Fei weir spillway and Baojiangkou water intake.