Chapter 32 Section 5 Guanzhong "Three Benefit Canals"

The water conservancy situation in Guanzhong farmland urgently needs to be improved.In modern times, since people were able to build strong concrete dams, the water level of the river could be raised to a high level safely, and it was no longer a problem to divert water from the Jing, Wei, Luo and other rivers into the canal.And because the level of sand damage treatment has also been greatly improved, a whole set of sand settling and sand discharge technologies has been mastered.So starting from the 1930s, under the auspices of Mr. Li Yizhi, a well-known water conservancy expert, the earliest new farmland irrigation project in China, the Jinghui, Luohui and Weihui three canals, was first built in Guanzhong.

Jinghui Canal uses Jingshui as its water source. Started in 1930, there are three main projects: one is to build a concrete rolling dam in Zhangjiashan, Jingyang County, so as to block part of the Jing water into the diversion canal.The dam is more than nine meters high, 17 meters wide at the base, four meters wide at the top, and 68 meters long.The second is to dig 11,230 meters of diversion canals.There are three tunnels, the longest of which is 359 meters.More than 1,800 meters in the front section of the diversion canal is a stone canal, which is made of stone and has a strong anti-scouring effect.The back section is the earth canal.At the end of the diversion channel, there are sedimentation ponds, backwater flushing sluices and intake sluices.The functions of the three are: to settle the sediment in the ditch water, to discharge the excess water and the sedimented sediment in the ditch, and to put clear water into the irrigation ditch.The third is to build irrigation canals in the irrigation area, mainly to transform the old canals, widen and deepen them.A total of 370 kilometers of main irrigation canals and branch canals were built.The whole project was carried out in two phases. The first phase was completed in 1932 and began to exert economic benefits.The second phase was completed in 1935, and 590,000 mu of farmland in Jingyang, Gaoling, Lintong and other counties were irrigated.

Luohui Canal uses Luoshui as its water source.It is a new canal system built on the basis of Longshou Canal in the Western Han Dynasty.During the construction, some remains of the shaft of the Longshou Canal were also found.It started construction in 1934, and the head of the canal is on the north bank of the Luoshui River in Lao (氵形) [zhuang] Tou Village, Chengcheng County.The main projects include: a barrage dam, 150 meters long, more than 16 meters high, 22.5 meters wide at the bottom, and 5 meters wide at the top, which is a concrete slurry block stone structure.In order to strengthen its anti-flood ability, it is built into an arc with the bow facing upward.Five diversion tunnels were dug, among which the Tiejianshan Tunnel is 3070 meters long. In order to overcome the collapse, the tunnels are lined.The total length of the diversion canal is more than 20,000 meters, and there are also sedimentation ponds, receding water flushing gates and intake sluices on the canal.In addition, the irrigation canals in Dali and Chaoyi (incorporated into Dali in 1958) counties should be improved.Due to the extremely difficult project of Luohui Canal and the impact of financial difficulties, it was not completed until Li Yizhi died of overwork in 1938.The project plans to irrigate 500,000 mu of land.

Among the three "Huihui Canals", the Weihui Canal is the largest.This canal, like the Chengguo Canal in history, uses the Weishui River as its water source. It was built in the north of the upper reaches of the Weishui River and started construction in 1935.It is also a water intake project with a dam, and the barrage was built in Weijiabao in the west of Meixian County.In order to strengthen the dam body, in addition to adopting the concrete structure, two steel sheet piles were built at the foot of the dam, with a depth of four meters.The crest of the dam is 500 meters long, more than three meters high and eight meters wide at the base.On the north bank, a canal is opened to divert water, and six diversion gates are built, each hole is 1.75 meters wide and 2 meters high.One kilometer downstream of the intake sluice, there are sedimentation ponds, flood discharge and sand sluice gates and intake sluices.The Weihui Canal plans to irrigate 700,000 mu of farmland in the five counties of Meixian, Fufeng, Wugong, Xingping, and Xianyang in northern Weibei, and the canals that need to be built are very long.And because there are many tributaries of the Weishui River flowing from the north to the south, a large number of aqueducts must be built in the canal project.Among them, the aqueduct of Hengqishui River is the largest, with a length of 72 meters.The buildings of Weihui Canal are mainly reinforced concrete, and its quality is the best in the construction of farmland water conservancy at that time. In 1937, the first and second phases of the project were completed, irrigated 170,000 mu of land, and then the project was suspended for a long time due to lack of funds.

Due to financial constraints, when Li Yizhi presided over the "Three Benefits" project, he had to adopt low-standard construction schemes, such as building low barrages and fewer reservoirs.In this way, even if the project is fully completed, there will still be a large amount of water loss in Guanzhong, and large areas of farmland will not be irrigated.After the founding of the People's Republic of China, in addition to completing the uncompetitive work of the Li family, the three major Huiqu canals were rebuilt according to higher standards.After reconstruction, the three Huiqu canals have been able to irrigate 5 million mu of farmland, far exceeding the highest level in history (Figure 9).

Almost at the same time as the construction of the three major Huiqu canals, in Guanzhong and Hanzhong, Li Yizhi also built a number of smaller irrigation canals with the word "Hui", such as the Meihui Canal in Mei County, the Heihui Canal in Zhouzhi, and the Laohui Canal in Hu County. Canals, Fenghui Canal in Chang'an, Hanhui Canal in Mian County, etc., together with the three major Hui Canals, are collectively called Shaanxi Bahui Canal.