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The position of China's water civilization in world hydrology

Abstract: the history of water civilization is an important symbol of the level of ancient human civilization. The Yellow River Basin, the Nile River Basin, the Two Rivers Basin and the Indus River Basin are the birthplaces of the four ancient civilizations in the world. Chinese water civilization, which originated in the Yellow River basin, is an important part of the world water civilization. Some other countries in the world have narrow territory or simple natural conditions, some have short history despite superior natural conditions, and some have a long history but few records, so as far as water civilization is concerned, the whole of Europe and America can only be compared with China. China has a rich history of water civilization, with first-class engineering, first-class technology, first-class theory and first-class scientists, which can represent the advanced level of the world at that time.

Keywords: current situation of water civilization

The history of water civilization is an important symbol of ancient human civilization. The Yellow River Basin, the Nile River Basin, the Two Rivers Basin and the Indus River Basin are the birthplaces of the four ancient civilizations in the world. Chinese water civilization, which originated in the Yellow River basin, is an important part of the world water civilization. Some other countries in the world have narrow territory or simple natural conditions, some have short history despite superior natural conditions, and some have a long history but few records, so as far as water civilization is concerned, the whole of Europe and America can only be compared with China. China has a rich history of water civilization, with first-class engineering, first-class technology, first-class theory and first-class scientists, which can represent the advanced level of the world at that time.

First-class engineering

Dujiangyan irrigation system

Dujiangyan is the longest dam-free water diversion project in the world. Located at the apex of Minjiang River alluvial plain, it can irrigate tens of millions of acres by itself, and has the advantages of water supply and shipping. It was built in the late Qin Dynasty (about 255 ~ 25 BC1year), and Li Bing presided over the construction.

Dujiangyan is a water control project that combines nature and manpower. Including Yu Zui (divided into the Minjiang River as the inner and outer rivers), Sha Fei Weir (diverting water to reduce sediment, which will burst automatically when the water is heavy), Baokou (now 20 meters wide and 40 meters high, with a small belly in the cross section), Baizhang Dike, herringbone Dike and Jingang Dike. Generally, it can ensure that there is enough water in an hour, and the irrigation area will not be flooded when the water is large. The wonderful Dujiangyan project is rare in the world, and Chinese and foreign water conservancy experts all admire its exquisiteness. It can last for a long time, which is related to its simplicity and rationality, and also to its scientific management measures. More importantly, it has become a carrier of inheriting culture, and people have paid special attention to it since ancient times.

Huanghe levee

The construction of the Yellow River levee can be traced back to prehistoric workers and guns. During the Warring States period, the vassal states along the river built dikes in their respective territories, which laid the foundation for systematic dikes. After Wang Jing ruled the river in the Eastern Han Dynasty, the new dike became a system, reaching Haikou for more than a thousand miles. During the period when the Yellow River seized the Huaihe River, the world's largest dike systems were formed in the lower reaches of the Yellow River, including remote dikes, connecting dikes, lattice dikes, moon dikes, sub-dikes, dikes, spur dikes and cut-off dikes. This is the old course of the Yellow River in Ming and Qing Dynasties that we can still see on the map today.

The present Yellow River levee is similar to the old road in the Ming and Qing Dynasties, which was gradually formed after the diversion of Tongwa Room in 1855. From Taohuayu in Zhengzhou to Lijin Estuary in Shandong Province, the river is 767 kilometers long, and the dikes on both sides of the river and other related dikes are 1583 kilometers long, with a general top width of 9 ~ 12 meters, a height of14 meters and a bottom width of tens of meters or even hundreds of meters. People vividly call it the "Great Wall on Water". The Yellow River levee is considered as a representative project to maintain the oriental civilization.

Jinghang canal

The Beijing-Hangzhou Canal is about 1800 km long and is the longest artificial canal in the world. In the 500 years before the appearance of the railway, it has been the lifeline for China to maintain national political stability and economic exchanges between the North and the South. The Beijing-Hangzhou Canal was expanded on the basis of canal projects in previous dynasties. The earliest section is called Hangou, which was cut in 486 BC. The Sui Dynasty opened the Grand Canal, which connected Beijing and Hangzhou in a zigzag way. The most critical project on the existing route was built in Yuan Dynasty. 1293 runs through the whole line, and 1688 is basically finalized.

The Beijing-Hangzhou Canal spans the Yangtze River, the Yellow River, the Huaihe River and the Haihe River, and crosses the Shandong horst. Due to the undulating terrain and lack of water resources, a large number of steep gates, shiplocks, water tanks and reservoirs have been set up along the canal, which involve complex hydraulic technology and sediment engineering technology, and are highly praised by Chinese and foreign scholars.

Hongze Lake

Hongze Lake is the fourth largest freshwater lake in China and the largest and oldest artificial plain reservoir in the world.

At present, when the water level of Hongze Lake is13m, it covers an area of 2,350km2 and has a storage capacity of 4.2 billion cubic meters. When the flood level17m, the lakeside polder was destroyed, with the maximum water surface of 4,345 square kilometers and storage capacity 176 billion cubic meters. It dampens the Huaihe River and provides flood control barriers and irrigation water sources for 20 million people and 30 million mu of land in northern Jiangsu.

Hongze Lake levee is a homogeneous earth dam, and its predecessor is Gaojiayan. During the overhaul of 1578, Gaojiayan was only 4 meters high and about 60 miles long. In order to raise the water level of the Huaihe River, the levee has been raised to about 10 meter, and the longest levee is 67.25 kilometers. Founded in 1580, the stone wall near the water was once 60. 1km long and the vertical height was 7 ~ 10m. It is sturdy and durable, just like the Great Wall on the water, and it is extremely spectacular. Now, because of the wind and waves, most of them have been transformed into gentle slopes to meet the water.

sea embankment

Seawalls are dikes to resist tides and typhoons, which are widely distributed in the southeast coastal areas. The seawall in western Zhejiang on the north bank of Qiantang River is the seawall with the longest history, the largest scale and the most advanced technology.

Seawall in western Zhejiang appeared in Qin and Han dynasties, originally as an earthen pond; Construction and restoration of stone ponds in Song Dynasty; It was changed to Shitang in Ming and Qing Dynasties. Many seawalls in the Qing Dynasty are still functioning after renovation.

The size of the ancient seawall is rare in the world. The total length of the main seawalls in Jiangsu, Zhejiang and other places is about 935 kilometers. During the Ming and Qing Dynasties, fish scales were large stone ponds, about 6 meters high; Foundation compaction piles and compacted concrete; Joints between stones are filled with putty or glutinous rice juice and nailed firmly with a spade (butterfly iron). Because seawalls play an irreplaceable role in protecting coastal economic development, all previous dynasties spared no effort and material resources. According to literature statistics, from 7 13 to 1780, there were 35 large-scale projects, with more than 10000 workers and ponds over 1000 meters, and countless small-scale projects. However, the records of similar projects abroad in the same period are rare.

Protective dike in lakeside area

Wei, also known as Wei and Yuan, is a closed production activity area formed by building a circular dike near the water area. Flood control and drainage and diversion irrigation are the main functions of this kind of projects. Therefore, sluice culverts should be built on dikes, and irrigation and drainage canals should be built in polder areas.

Embankments have been the main engineering measures to develop lake areas and areas along the river since ancient times. From the Tang and Song Dynasties to the Ming and Qing Dynasties, polder fields rose in large numbers in the plain areas in the middle and lower reaches of southern rivers and developed continuously. Small polder fields are tens of acres, and the largest can reach 200,000 acres, and often dozens or even hundreds of polder fields are connected together. Tangpu, Jiangnan, Dongting Lake, Poyang Lake and Pearl River Delta all have famous polder fields. These areas later became the most developed agricultural areas in China due to the foundation of building dikes and building water conservancy projects.

First-class technology

Dam worker

In ancient times, retaining dams had many names, such as dam, weir, dam, dike, dike, pond and pond. , widely distributed in the main tributaries of China's major water systems. Dam projects in China have a long history, such as Shaobei Reservoir in Anhui Province, which was built from 598 BC to 59 BC1year and is the earliest existing water storage project.

The types of ancient dam construction projects are complete and adapted to local conditions. In terms of types, there are barrage and overflow dam; From the material point of view, there are earth dams, wooden dams, brick dams, lime-soil dams, rockfill dams, masonry dams, wooden cage rockfill dams, bamboo cage rockfill dams, pile foundation masonry brick-lined rammed earth mixed dams and so on. And the design and construction are very scientific. During the Northern and Southern Dynasties, the Fushan weir spanned the Huaihe River, with a height of about 32 meters, which was the highest dam in the world at that time. Gaojiayan, not far downstream of Fushan weir, has a long history. Hongzehu reservoir barrage was rebuilt in Ming Dynasty, with a length of about 37 kilometers (later extended to 67.25 kilometers), which was the longest dam in the world at that time.

Daigong

Building technology is a creation of China's hydraulic technology. The craft originated in the pre-Qin period, and the mature technology is represented by silk reeling in the Song Dynasty and box reeling in the middle of Qing Dynasty.

Generally, silk reeling is made up of several silk reeling bundles according to certain rules. Each bundle is spread evenly layer by layer with "soft materials" such as willow tips, straws and reeds. Gravel and earth materials are compacted layer by layer, put on big ropes, and finally rolled into bundles like roller blinds. The diameter of the big bucket can reach several feet, and thousands of people can move it at the same time.

Box barrel technology is to lay a row of box boats outside the dike, lay ropes between the boats and the dike, bind the buckets on site, add soil, and laminate them one by one until they reach the bottom of the river.

There are many kinds of workers and they are flexible to use. Using local materials, it can be made into a giant in a short time. Straw, grass and other "soft materials" are flexible and easy to slide and stop siltation, so they are often used for bank protection and mouth closure of muddy rivers such as the Yellow River, which is particularly effective for temporary rescue and mouth closure.

Weir dam and compound sluice

The invention of ship lock is an important achievement of ancient shipping engineering technology in China. The invention of ship locks in China has gone through several stages, such as weir dam, sluice, single sluice and re-sluice.

In order to save water, the initial method is to build a low dam to stop the river every once in a while, which is called weir or dike.

The dam project appeared at the latest in the Three Kingdoms period. The upstream and downstream slopes of the weir are very gentle, so the tugboat can cross the dam along the inclined plane. When towing a big ship, it is necessary to erect winches on both banks and apply aquatic plants and silt on the weir surface for lubrication. This is the original inclined plane ship lift.

There were many Doumen, or single doors, on the Canal in the Tang Dynasty. There is also a record of "the second branch of the Yangtze River Jindoumen", which seems to be a double door, not very clear. The second Doumen of Xihe River in Chuzhou, founded by Song Renqiao in 984 AD, has alternating switches and ships passing through the gates. The literature is very detailed and clear, and it is an out-and-out heavy door (that is, a lock). Xihe locks are five or six hundred years earlier than similar locks in Europe.

Flood control works

Various flood control projects appeared on the main rivers in ancient China, the most prominent of which was the Yellow River. About 2 1 century BC, there was a legend in Egypt and China that dams were built on the Nile and Yellow Rivers to prevent floods. During the Warring States Period (5th century BC), China built dikes along the Yellow River to prevent floods. In the historical records, Sima Qian recorded the famous project of blocking the Yellow River estuary in BC 132. Subsequently, from 69 BC to 66 BC, three sharp bends were dug in the lower reaches of the Yellow River, and a dike-like revetment structure was built. In Song Dynasty, there were dikes, wooden dragon revetments and sliding revetments. In foreign countries, the Rhine bend cutting project in Germany was established in 18 17. In the Tang Dynasty, China excavated and reduced the river course to the east of Yongji Canal (now a section of South Canal) in Haihe River basin, and added a waterway to the sea. To the west of Yongji Canal, a large number of depressions are used to store flood detention, which reduces flood pressure and ensures navigation. In the Ming Dynasty, a dike system consisting of remote dike, connecting dike and lattice dike was built in the lower reaches of Pan Jixun Yellow River. Flood detention reservoirs have been built in Roman Lake and Hongze Lake, and many flood diversion and overflow dams have been built on both sides of the Yellow River, which has gradually developed flood control from a single measure to a comprehensive management combining various engineering measures, and from the management of local river sections to the comprehensive management of river basins. Many rivers, especially the lower reaches of the Yellow River, have formed a relatively complete flood control engineering system. Hydraulic machinery and water lifting tools

Ancient hydraulic processing machinery included water hammer, water mill, drainer and water hammer. According to records, water pheasants appeared in the Western Han Dynasty. Du Fu's poems in the Eastern Han Dynasty invented the water platoon. During the Southern and Northern Dynasties, water mills and water tables were widely used. Guanzhong water mill was very popular in the Tang Dynasty, and this technology was introduced to Tibet. During the Song and Yuan Dynasties, the water-to-water spinning wheel came out. This is a major change in the industrial technology of hydraulic machinery rivals.

According to documents, China began to use water lifting tools such as oranges and windlass as early as 2500 ~ 3000 years ago. Some people think that the history of oranges can even be traced back to 3700 years ago. In the Eastern Han Dynasty, Bilan invented the dumper (also called Gulong Reservoir) and the gondola car. Since the Tang dynasty, there has been a keel reservoir driven by animal power, wind power and water power.

Ancient Egypt and ancient Greece used slings (similar to oranges in China) to lift water almost at the same time as China. Water pumps (simple reciprocating pumps), Archimedes spiral pipes (simple spiral pumps) and Persian wheels (webbed wheels) also appeared in ancient Greece.

First-rate theory

Guandu Zidi

The crystallization of science and technology in the great development of water conservancy in pre-Qin period. It is emphasized that eliminating floods and developing water conservancy are the primary problems in governing the country. In canal planning, surface water is divided into main stream, tributaries, seasonal rivers, tributaries, artificial rivers and lakes. , in order to treat and use differently. In terms of design, it is suggested that the slope of open channel should not be too steep or too slow, and should be one thousandth; The movement laws and characteristics of open channel flow and pressure flow are preliminarily summarized, and the reasonable shape and size of canal system buildings are designed for destructive water flows such as hydraulic jump and curved circulation. In the flood control project, it is pointed out that: it is necessary to assign special personnel to inspect and repair, prepare in autumn and winter, and construct in spring; Trees should be planted on the dike to protect the shelter; Saline-alkali depressions will become flood detention areas and so on.

The full text of Guan Zi Du Di is only 2,000 words, but it reflects the outstanding water conservancy technology in ancient China and occupies a high position in the history of world civilization development.

Jia rang San ce

Jia Rang suggested in the Western Han Dynasty that the best way to control the Yellow River is to open up flood storage and detention areas, relocate land, implement wide dike spacing, and prohibit indiscriminate reclamation, occupation and land competition with water. He thinks that it can last for thousands of years without much cost, so it is called the best policy. The middle policy is: open canals and build sluices, set sluices, open yellow river sluices for irrigation in drought, and open flood discharge sluices to kill water anger in flood. This has three advantages: first, warping irrigation can improve the soil; Secondly, changing dry land into paddy field can increase yield; Third, it can develop shipping. He thinks this plan costs the least, but it can't be done once and for all, and it can only last for hundreds of years, so it is called China Strategy. The best way is to maintain the old dike and increase its height and thickness. There is no end to tinkering, so it is called the worst policy.

Jia rang's three strategies are the most important exposition of river management by later generations. Jia Zhen used the concept of economic comparison to criticize the simple dike policy, which had a far-reaching impact on the water control thought of later generations and was called the pearl in the treasure house of human water control thought.

Sedimentary theory

In terms of sediment theory, China has maintained a leading position in the world since ancient times.

From the Warring States Period to the Ming and Qing Dynasties in ancient China, all those who talked about river management talked about sediment. For example, in Guandi, it is discussed that the bend will cause the change of riverbed erosion and deposition, and Zhang Rong first put forward the idea of using hydraulic erosion and deposition. What is particularly commendable is that people can actively use the theoretical knowledge of sediment to solve the sediment problem in practice. There are five main types of sand control in ancient times. The first category is upstream soil and water conservation. This was put forward in the Southern Song Dynasty. Soil and water conservation and sand prevention measures include agricultural planting measures, valley warping dams, flood warping irrigation and warping. According to legend, mountain flood siltation began in the pre-Qin period. The second category is downstream sand control. There are five commonly used sand control strategies: water distribution and uniform sand, water control and sand attack, siltation and embankment consolidation, flood diversion and siltation promotion, and mud cleaning. The most typical example is the regulation of Haihe River system in Qing Dynasty. In the Ming Dynasty, Pan Jixun systematically put forward the theory of controlling water and attacking sand, vigorously implemented "controlling water with dikes and attacking sand with water" in the lower reaches of the Yellow River, and built the hongzehu reservoir at the junction of Huanghuai, "storing clear water, brushing yellow water and clearing muddy water". From the late Ming Dynasty to the Qing Dynasty, silting, dike consolidation, flood diversion and sediment discharge irrigation were widely practiced on sandy rivers in the north, and the systematic experience was summarized. The third category is silt and silt irrigation. Farming with silt and fertile land has a very old origin. Natural siltation can be traced back to prehistoric times, and artificial siltation has a history of thousands of years. The fourth category is river sand control. In ancient times, in addition to manual dredging, sand was washed or settled by changing the cross section of the river. For example, in the Song Dynasty, a narrow embankment was built on the Bianhe River to prevent siltation, and muddy water was turned into clear water through a grit chamber (lake). The fifth category is gully sand control. During the Ming and Qing Dynasties, there was a theory of controlling sand by dividing water into rivers and dividing sand into fertile fields.

hydrology

China's ancient water cycle theory was recorded in Lu Chunqiu during the Warring States Period. The spring flows eastward day and night ... "It accurately reflects the objective law of water cycle in land and sea areas where China is located. Hydrological testing has a long history. Archaeological excavations show that Li Bing began to observe the water level with the stone statues of Dujiangyan project during the Warring States Period, and other areas also preserved the "water gauge" of past dynasties. Since the Tang Dynasty, there has been an inscription of low water (stone fish) on the "Baiheliang" of the Yangtze River in Fuling, Sichuan. As for flood marks or inscriptions, there are countless ones all over the country. In terms of rainfall observation, the Qin dynasty had a system of reporting rain to the central government; Qin, a mathematician in the Southern Song Dynasty, also put forward various methods to calculate rainfall and snow with rain gauges. In the Forbidden City in the Qing Dynasty, there was a record of rain on a sunny day. According to 12 o'clock, the precipitation in Beijing was recorded from 1724 to 1903. During the period, the data was 174, and it was around the clock. The origin of sediment measurement is also very old. " "One Shi Shui, six buckets of mud" is a common understanding of the Yellow River and Jinghe River in the pre-Qin period. As for the velocity, the cross section of the river was measured in square feet in the Song Dynasty, and the velocity was qualitatively described by the "turbulence" of the water flow, which initially formed the concept of velocity. In the Yuan Dynasty, one square foot was called "foot", and the amount of water calculated by foot was called "waterway" or "straight water". The method of measuring the water flow through a certain section in unit time was put forward by Huang Chen in Kangxi period of Qing Dynasty, and the emperor Kangxi himself described it more clearly: "Measure the width of the sluice first, and calculate the geometry of the flow in one second. "This is completely in line with the modern transportation concept.

The ancients have long summed up the ups and downs of rivers. Qin and Han dynasties were known as "peach blossom water" and "autumn water". In the Northern Song Dynasty, every month's flood and ebb had a special name. People thought that the flood and ebb of the river were regular, so they named it "faithful water" (trustworthy water). In the Ming and Qing dynasties, the concept of believing in water was replaced by the "flood season" and has continued to this day. The fast-horse flood reporting system began at the latest in16th century.

Hydrological tests in ancient China have a glorious history and solid records, so that experts at home and abroad will call the history of hydrological tests Egyptian and China. However, China's ancient hydrology theory is described qualitatively and quantitatively, and it has not been developed in measuring tools, mathematical calculation and model tests, so that it lags behind the West in modern times.

Water conservancy literature

China has the largest number of ancient water conservancy documents in the world. The existing water conservancy monographs include general history, special history, river course history, regional water conservancy history, canal pond history, dam history and so on. And it is roughly estimated that there are more than 300 kinds. There are also a lot of water conservancy records in official history, political books, various local chronicles, local chronicles, county chronicles and geography books. Coupled with the records of water conservancy deeds in various works, the number of words is above 1 100 million. The earliest water conservancy masterpiece in history is Shangshu Gong Yu, which was written in the Warring States Period (480-222 BC) and described the legend of Dayu's water conservancy. The earliest summary of water conservancy science is Guan Zi Du Du. China's first general history of water conservancy is Historical Records of Rivers and Channels. The first monograph describing water system in China was Water Mirror, which was written in 220 ~ 232 AD. The earliest existing monograph on river engineering technology is General Theory of River Prevention, written in 1048. The ancient water conservancy works have the most collections: Golden Mirror of Running Water, Golden Mirror of Continuing Running Water and Golden Mirror of Continuing Running Water, with more than ten thousand words 19 1 1 year, * * * 10. Other famous works include "Water Control Hooves", "A Survey of River Prevention" and "General Plan for River Regulation". Rich water conservancy documents record history, discuss theory and guide practice, which has played a vital role in promoting the development of water civilization in China.

First-rate water conservancy scientist

Li bing

Li Bing was a hydraulic scientist in the Warring States Period and the founder of Dujiangyan. He also studies astronomy and geography. In the last years of Qin Zhaowang (about 256 BC ~ 25 BC1year), he was responsible for the construction of Dujiangyan project at the exit of Minjiang River in Dujiangyan City, Sichuan Province, thus making the western Sichuan plain rich. According to the Records of Huayang National Records, Li Bing once installed a water gauge in Dujiangyan, which was an early water level observation facility in China. He also dug beaches and dredged waterways in today's Yibin and Leshan, built irrigation and shipping projects such as Wenjing River (now Xihe in Chongqing County), Mubai River (now Nanhe in Qionglai County), Luoshui River (now Shiting River) and Mianshui River (now Mianyuan River), and built cable bridges and opened salt wells. People miss his achievements and build temples to commemorate them. After the Northern Song Dynasty, there was a myth that Li Bing's son Li Erlang helped Li Bing to control water.

Wang Jing

At the beginning of the Eastern Han Dynasty (AD 69), after Wang Jing ruled the river, there was almost no record of the Yellow River flood in history books for hundreds of years, so there was the saying that "Wang Jing ruled the river for thousands of years". But whether it is "not bitter for a thousand years", Wang Jingzhi has really contributed a lot to the rivers and lakes. This time, hundreds of thousands of people were used to harness the river, stretching for more than 1000 miles from Xingyang to Haikou, and its scale was unprecedented in ancient times. In addition to conventional dredging and embankment construction, its outstanding measure is to build a sluice ten miles away to make it more attractive. Wang Jing is the inventor of "branch flow method" (lateral overflow weir flood discharge technology), which is also very close to the time when Jia Zhen put forward the idea of "adding more sluice gates to divide the Yellow River" (about 6 BC). Therefore, some scholars infer that Wang Jing partially turned Jia Rang's idea of China's middle policy into reality, and adopted the technology of building gates to control the diversion of the Yellow River, at least in the diversion of the Yellow River and Bianhe River. Many scholars believe that this is also the key to the success of water control in Jing Wang. Jing Wong built sluice gates on such a big river as the Yellow River to manually control the water flow, which is an unprecedented initiative in the history of human water civilization and a rare wealth.

Guo Shoujing

Guo Shoujing (1231-1316) was an outstanding scientist in Yuan Dynasty. He is good at water conservancy and astronomical calendar calculation, and he is "ingenious". He used to be the water supervisor, Taishiling. On the eve of the opening of the Shandong section of the Beijing-Hangzhou Canal, he did a lot of exploration and survey work in the Hetao area of Ningxia, the Beijing-Hebei-Henan area and the Wensihe area, put forward more than 20 water conservancy suggestions and managed hundreds of canals and ponds.

Near the Yuandadu (present-day Beijing), he presided over the reopening of Jinkou River to divert Yongding River, and presided over the construction of Tonghui River project that eventually opened the entire Beijing-Hangzhou Canal. Guo Shoujing has designed and manufactured 20 kinds of astronomical instruments, carried out astronomical geodesy in north-south 1 1000 Li and in east-west 6000 Li, and completed the chronicle of 1280. He first put forward the concept of "altitude", more than 560 years earlier than the German mathematician Gauss.

Pan jixun

Pan Jixun (152 1- 1595) was a famous river expert in Ming Dynasty. He was the "River of Prime Ministers" for four terms, presided over the management of the Yellow River, Huaihe River and Canal, and made great achievements in the theory and practice of river management. In view of the loose river regime at that time, he built dikes on both sides of the Yellow River below Xuzhou and pulled the river back into the trough to realize the attack of water and sediment; Block the breach of Gaojiayan, reinforce Gaojiayan levee, and force Huaishui to clear its mouth and yellow; Hongze Lake is used to store the Huaihe River flood and supply water for the canal. He also put forward measures to strengthen dikes by using the scouring and silting laws of the Yellow River itself. The Ming and Qing rivers laid the foundation by him have been maintained for 300 years. His theoretical contributions are mainly as follows: ① He raised sand control to the height of the general plan of harnessing the Yellow River, and realized the transformation of the general plan of harnessing the Yellow River from water diversion to water control, and from simple water control to attaching importance to sand control. (2) Three measures to solve the problem of sediment in the Yellow River are put forward and implemented, namely, pumping water to attack sediment, storing fresh water to brush the Yellow River, and silting beaches to reinforce dikes. (3) He wrote a book "Introduction to River Defense", which systematically summarized and improved a set of dike maintenance systems and measures. Later generations commented: "As long as the river management personnel can remember one or two sentences in his book, the measures proposed must be excellent."

Li Yizhi

Li Yizhi (1882- 1938) is a famous hydraulic scientist and educator in modern China. He studied in Germany to study water conservancy in his early years. 19 15 after returning to China, he worked as a professor and principal in Nanjing Hehai Engineering College, the first water conservancy school in China, and later served as director of Shaanxi Water Conservancy Bureau, chairman of Yellow River Water Conservancy Commission and chief engineer. In Shaanxi, he used modern technology to plan the "Guanzhong Eighth Meeting" irrigation area, and personally participated in the construction of Jinghui Canal, Luohui Canal and Weihui Canal. 1933 Established China No.1 Hydraulic Laboratory in Tianjin. Li Yizhi attaches great importance to the introduction of western advanced water conservancy technology. Through the regulation planning of the Yellow River, Huaihe River and Yangtze River, it introduced many advanced western water conservancy science and technology into China, and also trained a large number of modern water conservancy talents. 193 1 initiated the establishment of the first water conservancy academic group in China-China Water Conservancy Engineering Society, and was elected as its president until its death.

In modern history, China's ancient water civilization has lagged behind the West in some aspects. Li Yizhi is one of the representatives who promoted the integration of water civilization between the East and the West in this period.