Chapter 28 Chapter 6 Farmland Water Conservancy in Guanzhong in the Past Dynasties

The first large-scale water conservancy project to be built in Guanzhong was the Zhengguo Canal dug by the Qin State in the late Warring States period.The reason why this project was built at that time was that apart from the natural conditions mentioned above, another factor was political and military needs. During the Warring States period, the history of our country was developing towards the establishment of a unified country. Some powerful princes and states wanted to unify the whole country with themselves as the center.The annexation war was fierce.Guanzhong is the base of the Qin State. In order to strengthen its economic strength and remain invincible in the annexation war, it needs to develop the farmland and water conservancy in Guanzhong to increase the grain output of the Qin State.

South Korea is Qin's eastern neighbor.At the end of the Warring States Period, among the seven kingdoms of Qin, Qi, Chu, Yan, Zhao, Wei, and Han, when Qin's national strength was flourishing, and it was eyeing the tiger, and wanted to do something to the East, South Korea, which bears the brunt, was so weak that it could not be attacked at any time. Annexed by Qin.In 246 BC, King Han Huan adopted a very clumsy so-called "tired Qin" strategy when he was desperate.He used Zheng Guo, a well-known water conservancy engineer, as a spy, and sent him to Qin to lobby Qin to build a large irrigation channel between Jingshui and Luoshui (Northern Luoshui, a tributary of Weishui).On the surface, it is possible to develop Qin's agriculture, but the real purpose is to exhaust Qin's strength.

This year is the first year of King Qin Yingzheng.Qin State, which originally wanted to develop water conservancy, quickly adopted this attractive suggestion.And immediately collected a lot of manpower and material resources, appointed Zheng Guo to preside over the construction of this project.During the construction process, the conspiracy of "Tired Qin" in South Korea was revealed, and King Qin was furious and wanted to kill Zheng Guo.Zheng Guo said: "The first minister is the intermediary, but the success of the canal is also the benefit of Qin. The minister is the life of Han Yan for several years, and the merit of Qin's construction forever." A farsighted politician thinks what Zheng Guo said is very reasonable. At the same time, Qin's hydraulic technology is still relatively backward, and Zheng Guo is also needed in terms of technology, so as always, he still reuses it.After more than ten years of hard work, the whole canal was completed, known as Zheng Guoqu.

The Zhengguo Canal is a water conservancy project that uses the Jing River as the water source to irrigate the farmland north of the Wei River. Both "Historical Records Hequshu" and "Hanshu Gouweizhi" say that its canal head project starts from Zhongshan in the east and ends at Huhukou in the west.Zhongshan and Hukou were later called Zhongshan and Gukou respectively. They were all located in the northwest of Jing County, looking east and west across Jingshui.It is a water diversion project with a dam. From 1985 to 1986, archaeologist Qin Jianming and others conducted field investigations on the canal head project of Zhengguo Canal. After investigation and drilling, they found the remnants of the dam that intercepted Jingshui.It starts from the high slope named Jianzui 1,800 meters away from the east bank of Jingshui River in the east, and ends at the hilltop in the south of Wangliwan Village, more than 100 meters away from the west bank of Jingshui River in the west, with a total length of more than 2,300 meters.Among them, 350 meters on the river bed have been washed away by floods, and there is no trace to be found, while other remaining parts can be seen vividly.It has been determined that these remnants have a bottom width of more than 100 meters, a top width of 1-20 meters, and a remnant height of six meters.It can be imagined that this project was very grand in those days.

Regarding the channels of Zheng Guoqu, "Historical Records" and "Hanshu" all remember very briefly, and "Shui Jing Zhu · Ju Shui Zhu" is more detailed.According to the records in ancient books and the field investigation of modern people, generally speaking, it is located at the southern foot of Beishan Mountain, on the highest position of the second-level terraces in Jingyang, Sanyuan, Fuping, Pucheng, Baishui and other counties. From west to east, the gradient is 0.64/00, Along the line, it intersects with Yeyu, Qingyu, Zhuoyu, Juqi (now Shichuan River) and other waters.Arranging the main canal at a higher position on the northern edge of the plain is convenient for digging branch canals to go south to irrigate the large farmland in the south.It can be seen that the design at that time was relatively reasonable, and the level of measurement was already very high.However, Jingshui is a famous sandy river. In ancient times, there was a saying that "a stone in Jingshui contains several buckets of mud". The actual measurement in contemporary times is 171 kg/m3. The Zhengguo Canal uses the sandy Jingshui as its water source. Too small.The gradient is small, the flow velocity is slow, the sediment is easy to deposit, and the channel is easy to be blocked.

After the canal was completed, the economic and political benefits were remarkable. Both "Historical Records" and "Hanshu" said: "The canal is used to fill the water of the silt (silt) and irrigate more than 40,000 hectares of the land of the Xi (xixi) bittern. Every mu is one bell, so Guanzhong is a fertile field, and there is no evil year. Qin became prosperous and strong, and died and the princes, so it was named Zheng Guoqu." One bell is six stones and four buckets, which is many times higher than the average yield of one stone and a half per mu in the middle reaches of the Yellow River at that time. .

At the end of the Warring States period, Qin State had more than 40,000 hectares, which is about 28,000 hectares today.Some scholars believe that this figure is not true.Starting from the fact that the average annual flow of Jingshui is about 50 cubic meters per second, and each flow can only irrigate 200 hectares of fields, they say that the Zhengguo Canal can only irrigate 10,000 hectares of land at most. The so-called 40,000 hectares is a false report by Zheng Guo.Zheng Guo has already offended Qin State once because of deception, it seems that he will not have the guts to cheat again.Zheng Qu's large area of ​​irrigated fields is suspected to be related to the following two situations.One is that the amount of rainfall in history has fluctuated a lot, and the past cannot be ruled by the present.According to the famous meteorologist Zhu Kezhen's "A Preliminary Study on China's Five Thousand Years of Climate Change", the Eastern Zhou Dynasty, Qin and Han Dynasties were the warmer periods in our country. The temperature and humidity in the south moved northward, and the rainfall in the north increased. "Historical Records Huozhi Biography" has a record of "a thousand acres of bamboo in Weichuan".The second is that ancient and modern crops are different.In ancient Guanzhong, the main crops were millet and broomcorn, which consume less water and are resistant to drought, but after Tang Dynasty, wheat and cotton, which consume more water, were the main crops.In the Qin and Han Dynasties, more water was used to irrigate water-saving crops, and the area of ​​irrigated fields would of course be much larger than today.