Located in Hongze District, Huai’an City, Jiangsu Province of China, the Hongze Lake Irrigation System lies in the Huai River Basin, on the east of the Hongze Lake, the fourth largest freshwater lake in China. With an irrigated area of 32,087 ha, the System stretches from the Hongze Lake Levee in the west to the Baima Lake in the east, and from the sea-entering waterway of the Huai River in the south to the Subei Irrigation Main Canal in the north.

The Hongze Lake Levee helps store water for the Irrigation System. The construction of the Levee started in the Eastern Han Dynasty (25 AD-220 AD) and matured in the Ming Dynasty. By the Qing Dynasty, it had been largely finalized. Built with more than 2.7 million stone slabs each of which weighs more than 500 kilos, the Levee is 67.25 km long, and its storage capacity had reached over 1 billion m3 in the Ming Dynasty. The upright masonry, the gently sloping revetment, the dams and sluices for the purpose of flood discharge, and the leak-proof tabia dam surface are all major inventions applied during the construction of the Levee. Having protected the downstream of the Huai River from flooding since ancient times, the Levee is a comprehensive project used for irrigation, flood control, domestic water supply, and ecological functions. Currently, more than 2 million ha of farmland, 26 million people, and a dozen major cities are under its protection.

First built in 199 AD, the System has undergone three stages of development, namely the Pofu Lake Stage, the Baishui Lake Stage, and the Hongze Lake Stage. In 1128 AD, the Yellow River changed its course to flow southward and occupied the course of the Huai River. Depending on the downstream of the Huai River for water supply, the System was heavily affected by this incident, as its functions shifted from pure irrigation to flood control and irrigation, and its scope and size also altered radically.

As a historic and sustainable mega project, the System incorporates the functions of water storage, water diversion, water delivery, and drainage.

Flood Control: The Hongze Lake Levee ofthe System has protected the lower reaches of the Huai River from flooding since ancient times. When theits predecessor, the Gaojia Levee,was constructed in the late Eastern Han Dynasty under the command of Chen Deng, its  purpose is to prevent the flooding of the Huai River. Before the Yellow River occupied the course of the Huai River, the Gaojia Levee had effectively protected the downstream area. After the Yellow River changed its course in 1128, the outlet of the Huai River and the Hongze Lake to the sea was eventually silted and blocked. In 1577, the Gaojia Levee bursted, leading to severe flooding downstream. Later in 1578, Pan Jixun presided over the construction of a 35.9-km-long earth levee which stretched from Wujiadun to Yuecheng; in 1580, people began to build masonry revetment on the base of the earth levee; two and a half years later, the 10-km-long revetment (from the south of Wujiadun to the north of Gaoliangjian) was completed, greatly improving the Levee’s resilience to floods. During the Ming and Qing Dynasties (1368-1912), 26 sluices and spiilover dams were built along the Levee for the purpose of flood discharge. Together, the Levee and the spillover dams and sluices formed a complete flood control system which had reduced the impact of flooding on the upper and lower reaches of the Hongze Lake. 

After the founding of the People’s Republic of China, the Hongze Lake Levee has been further reinforced.New projects such as the Sanhe Sluice, Gaoliangjian Sluice, Erhe Sluice, and the Sea-Entering Watercourse of the Huai River have been constructed. As its resilience to flooding improves, the Levee has stood the test of multiple large-scale floods, releasing20 billion m3of flood water annually on averageand ensuring the sustainable development of local economy and society.

Ecological benefits: The Hongze Lake Levee has helped expand the Lake, forming a vast expanses of wetlands. With sound eco-system and beautiful landscape, the wetlands have improved the local environment, providing habitat for many protected animals and plants.

Since its inception in AD 199, the Irrigation System has constantly bolstered the development of local agriculture, economy and society. With its irrigated area growing from 12,000 ha to the current 32,087 ha, it has safeguarded the agricultural production in the north of Jiangsu Province, China. Having protected the downstream of the Huai River from flooding since ancient times, its Hongze Lake Levee is a comprehensive project used for irrigation, flood control, domestic water supply, and ecological  functions. Currently, more than 2 million ha of farmland, 26 million people, and a dozen major cities are under its protection. From AD 199 to the Ming Dynasty (1368-1644), the Irrigation System was where the troops were stationed to reclaim land for agricultural production. By helping feed the army and the civilians, it strengthened the process towards national unity. 

During the Ming and Qing Dynasties, the grain transport through the Grand Canal from the south of China to the capital Beijing was the lifeblood of the country, as it helped feed the north of China and served as the source of pay and provisions for troops stationed around Beijing and at the frontiers in the north. Standing at the intersection of the Yellow River, the Huai River, and the Grand Canal, the Hongze Lake Levee was key to keeping the boat sailing as it helped store clear water and prevent the watercourses from silting up.

The Hongze Lake Levee helps store water for the Irrigation System. The construction of the Levee started in the late Eastern Han Dynasty after AD 199 and matured in the Ming Dynasty. By the Qing Dynasty(1644-1912), it had been largely finalized. Built with more than 2.7 million stone slabs each of which weighs more than 500 kilos, the Levee is 67.25 km long, and its storage capacity had reached over 1 billion m3 in the Ming Dynasty. 

Since 1580, people began to build upright masonry to reinforce the Levee. The masonry has four vertical layers. Directly facing the water is the stone-slab wall. Next to the stone wall is a brick wall. The next layer is a loam wall. The brick wall serves as a buffer since its rigidity is between those of stone and earth. Between the brick wall and the loam wall, there is an additional layer of tabia for the purpose of seepage control. To prevent the masonry from collapsing due to foundation deformation, pile foundation was adopted: quincuncial piles or soldier piles were driven into the foundation for the purpose of reinforcement. The stone slabs were laid in a “block bond” way and sealed by lime mixed with glutinous rice paste. In addition, the slabs were joined together with iron ingots.

To reduce the impact of waves, two measures were adopted. First, a pile wall was set up in front of the stone-slab wall, and straw mats filled with grass and earth are laid between the two walls for the purpose of energy dissipation. Then gently sloping revetments were built next to the stone and pile walls; this kind of structure could not only reduce the impact of wind and waves, but also enlarge the cross section of the Levee and thus reduce the amount of earth work needed behind the Levee. When water is released through sluices or dams on the Levee, the flow could be so strong that the foundation of the sluices or the dams could be scoured and hollowed. To solve this problem, the ancients used culverts to divert some of the water to the immediate downstream of the sluices or dams to form a “water cushion” which could help dissipate the energy of the water released directly through the sluices or dams. In addition, tabia dam surface was adopted to prevent seapage, improve strength, and maintain a smooth passage for the overflow.

Throughout its long history, the Hongze Lake Irrigation System has formed a distinctive way of construction and management to maintain sustainability. For instance, the masonry of the Hongze Lake Levee was constructed in a segmented way, and each section was inscribed with the name of the person responsible for the construction, the date of construction, and the length of the section, which had been an effective way of quality control and ensuring accountability and responsiveness. For the management of the Levee, civil officials were responsible for regular operation and maintenance, while military officers were in charge of dealing with emergencies during flood season; apart from the government and the army, the civil society was also fully mobilized in times of floods. Such a comprehensive and mutually reinforcing system is similar to what China adopts now for flood control. The water level management and flood discharge mechanism of the Hongze Lake guaranteed the security of the Levee while ensuring agricultural production at the up-and downstream, which has been a good example of dam and sluice scheduling set by the ancients. In addition, in order to keep the officials in charge motivated for better quality of work and ensure adequate funding for management and maintenance, the officials responsible for the construction of the Levee would have to bear part of the cost of repairs and reconstructions once the Levee broke.

Since its inception in AD 199, Hongze Lake Irrigation System has constantly bolstered local agricultural and economic development, and safeguarded the agricultural production in the north of Jiangsu Province.

The System is located in the Huai River Basin, where precipitation fluctuates drastically between years and seasons, leading to frequent floods and droughts. In AD 199, Chen Deng, the chief of Guangling Prefecture, stationed troops near the Pofu Lake and diverted its water for irrigation. Later in AD 241, Deng Ai, another local official, connected the Pofu Lake with the Baishui Lake; he ordered the construction of 3 weirs and 8 watergates for the purpose of irrigation;and the irrigated area reached 12,000 ha. The agricultural development had continued. By the Yuan Dynasty (1279-1368), the farmland around the Hongze Lake had reached 35,300 ha. Historially, irrigation and land reclamation in this region provided the troops and civilians sufficient food supply, promoted local economic growth and social stability, and strengthened the process towards national unity.

After the founding of the People’s Republic of China in 1949, the System witnessed the construction of modern infrastructure such as the Sanhe Sluice, Gaoliangjian Sluice, Zhouqiao Culvert Sluice, Hongjin Culvert Sluice, Subei Irrigation Main Canal, etc. which have helped guarantee sufficient water supply for irrigation downstream. Currently,the irrigated area of the System is 32,000 ha.

The Hongze Lake Irrigation System has given birth to a variety of intangible cultural heritage, including customs, traditional dances, myths and folk tales, poetry, and great names in the history of water management, all of which have enriched local cultural life and further increased the cultural diversity of the Chinese nation.

Water Source: In 199 AD, Chen Deng, the Chief of Guangling Prefecture, selected the Pofu Lake as the water source and started the construction of the Irrigation System. In 241 AD, Deng Ai, another local official, connected the Pofu Lake with the Baishui Lake which functioned as the System’s water source thereafter till the Yuan Dynasty (1279-1368). Later, based upon the original Gaojia Levee, the embankment of the water body was enhanced and extended multiple times by the governments of the Ming (1368-1644) and Qing (1644-1912) Dynasties. By 1578, the Hongze Lake had taken shape, inundating the Lakes of Pofu and Baishui. Since then, Hongze Lake has served as the water source for the Irrigation System.

Water Storage Project: The Hongze Lake Levee helps store water for the Irrigation Sytem. The construction of the Levee started in the Eastern Han Dynasty (25 AD-220 AD) and matured in the Ming Dynasty. By the Qing Dynasty, it had been largely finalized. Built with more than 2.7 million stone slabs each of which weighs more than 500 kilos, the Levee is 67.25 km long, and its storage capacity had reached over 1 billion m3 in the Ming Dynasty. The upright masonry, the gently sloping revetment, the dams and sluices for the purpose of flood discharge, and the leak-proof tabia dam surface are all major inventions applied during the construction of the Levee. Having protected the downstream of the Huai River from flooding since ancient times, the Levee is a comprehensive project used for irrigation, flood control, domestic water supply, and ecological functions. Currently, more than 2 million ha of farmland, 26 million people, and a dozen major cities are under its protection.

Water Diversion Project: When the Baishui Lake was first used as the water source, 8 water gates were installed to divert water for irrigation. From the Ming Dynasty to the more recent times, the water gates were replaced by the culverts on the Hongze Lake Levee. By contemporary times, the culverts have been replaced by Zhouqiao Culvert Sluice, Hongjin Culvert Sluice and Gaoliangjian Sluice, and the remains of the old culverts are preserved. The Zhouqiao Culvert Sluice serves as the water intake for the Zhouqiao Irrigation Scheme which lies in the north of the Hongze Lake Irrigation System, while the Hongjin Culvert Sluice functions as the water intake for the Hongjin Irrigation System which stands in the south.

Water Delivery Project: During the Tang Dynasty (618 AD-907 AD), Baishui Lake was equipped with five main canals, namely the Qingzhou Canal, the Xuzhou Canal, the Zhuzi Canal, the Dafu Canal, and the Tangli Canal. They diverted water from the west to the east. Since the formation of the Hongze Lake in the Ming Dynasty, these irrigation canals had taken up other functions of flood discharge and drainage. Currently, the Qingzhou Canal is no longer in use, and its remains are preserved; the others mainly serve as drainage canals, but their irrigation function is performed by newly built canals. 

Drainage Project: During the Ming and Qing Dynasties, apart from the old canals from the Stage of Baishui Lake, new drainage canals had been excavated and dredged, including the Laosan Canal, the Jiangjiazha Canal, the Ren Canal, the Yi Canal, and the Li Canal. The Hongze Lake Levee was equipped with a complete water discharge system incorporating sluices, dams and culverts. After the founding of the People’s Republic of China, the old water discharge system of the Levee has been replaced by the Sanhe Sluice, the Erhe Sluice, and the Gaoliangjian Sluice.

Since the founding of the People’s Republic of China, the Chinese government has launched multiple rounds of rehabilitation for the Irrigation System. With fast economic development and accelerating urbanization, the System is facing changing water conditions and infrastructure status. There are some potential risks. For instance, some sections of the Hongze Lake Levee do not meet the seepage control standards, and improvements are needed; more wave protection works are needed, and the pile foundation of some sections of the masonry is rotten; at some sections of the Levee, the elevation of the levee crest does not meet the established standard; some area of the Levee is not covered by the existing surveillance system; as the number of tourists visiting the Hongze Lake grows, the surveillance system needs to be upgraded.