Xinghua Duotian Irrigation and Drainage System is located in the hinterland of the Lixiahe Plain on the eastern coast of Jiangsu Province, China, a region with a dense network of rivers and abundant water resources.

More than 7000 years ago, during the Neolithic period, the Lixiahe plain was a gulf between the Yangtze River and the Huaihe River. As the coastline moved eastward, this area formed into an enclosed lagoon and then gradually into a plain. To prevent seawater intrusion, Changfeng Weir and Fangong Dike were built during the Tang and Song Dynasties between the 8th and 11th centuries AD. This created a coastal barrier of about 300 km in length, laying the spatial foundation for future agricultural development within the plain.

From 1194 to 1855, the Yellow River encroached on the lower reaches of the Huaihe River to enter the sea, bringing frequent flooding and large amounts of sediment to the Lixiahe area and silting up the local lakes and swamps. During this period, in response to the frequent flooding, local people dug canals in shallow water and mounded the earth into elevated platforms, or Duotian as called by the locals. After years of hard work, these raised fields were gradually transformed into arable land. These elevated platforms are often built in strips to facilitate construction and later cultivation using a boat and to ensure smooth water flow.

In its early days, Duotian was formed to withstand flooding by virtue of height. Traditionally, Duotian could generally reach a height of around 5 m, and even the low ones could be 2 to 3 m high. To further protect the raised fields from floods, small dikes were built around them from the 18th century onwards. Gradually, they linked together to form larger dikes.

After 1949, the government began to build even larger dikes with gates and pumping stations for drainage and flood discharge, which greatly enhanced Duotian’s flood control capacity and stabilized its water level. Since the raised fields no longer need to rely on their height for flood control, their height is reduced to 1 m to expand arable land and for the ease of cultivation.

Duotian is irrigated using bailing buckets. When the water level is high, people stand on boats and irrigate the fields with water directly bailed from the canals. When the water level is low, people water the fields by forming a water-bailing cascade. For the highest field, the cascade would have 4 to 5 stages.

Due to its geographic uniqueness, Duotian is not suitable for modernized farming tools and thus largely maintains the traditional way of farming, such as bailing water for irrigation and using silt as fertilizer. Only a small part of the fields are irrigated using motor pumps installed on boats. Surrounded by water on all sides and with steep slopes, the raised fields are subject to erosion by both rain and river water, but local farmers have drawn a collection of soil and water conservation measures from centuries of hard work.

Duotian’s water level is high in summer and autumn and low in winter and spring. When the water level is low, people raise the height of the fields with the silt scooped out from the canals to prepare for possible flooding.

After the harvests in summer and autumn, people throw the rest of the crops into the canal to produce wet compost. In winter and spring, this natural and organic fertilizer is applied to crops.

The abundance of water combined with the high fertility of the soil has enabled the raised fields to produce high-quality fruits and vegetables since ancient times. Vegetable production has become one of the main sources of income for local farmers. The unique water landscape, sound ecological environment and varied folk customs and culture are all valuable resources for the local tourist industry. Famous scenic spots such as the rapeseed Duotian, the forest on water, the wetland park and the fishing eco-park serve as a key drivers for the local economy.

Duotian is a unique creation in the Lixiahe area. Adapting to and transforming nature at the same time serves as the basis for the local development of agricultural irrigation and water transport and as the source of rich culture. Today, it continues to provide fundamental support to local social and economic development and ecological security. As the cultural heritage of this agrosystem, the Duotian temple fairs, the stilted dragon dance of Gaojiadang, the Duotian singing festivals, farmer painting, and Shipohua painting all enjoy great vitality and local characteristics.

The structure made outstanding contribution to enhancing food production, livelihood opportunities, rural prosperity, and poverty alleviation in a region;

The establishment of the Duotian Irrigation and Drainage System has improved the regional natural environment and conditions of social and economic development, promoted the development of agriculture in the whole Xinghua region, and increased the grain output and population carrying capacity. According to the records of the Revised Xinghua County Annals, at the beginning of the Qing Dynasty, there were only more than thirty thousand residents, and the number increased ten times in two hundred years.

The structure is an example of attention to environmental aspects in its design and construction;

The Duotian system also has ecological functions, and the most prominent is the flexible allocation of water resources. The ditches and the inner rivers, as well as the surrounding lakes and rivers, constitute a perfect drainage network with a strong function of flood detention, drainage and irrigation. Secondly, Duotian, as a secondary wetland, has an obvious land-water edge effect and rich biodiversity. With agriculture, forestry and fishery as the central link, it builds a biological chain with very close internal connection and forms a complex and diverse ecosystem with land-water interaction.

The farmers in Xinghua Duotian have accumulated rich experiences in the development of shoal land and adopted the multi-level spatial and multi-sequence temporal structure in the utilization of the natural resources of shoal land. The multi-level spatial structure refers to the organic combination of forest, grain and fish so that the space above ground and underground can be fully utilized. The multi-sequence in time refers to the reasonable arrangement of planting crops in different seasons, which can help obtain relatively high economic returns on inter-crop under the premise of guaranteeing the good growth of trees. In order to make full use of the space resources, the farmers not only plant vegetables in a large area on the Duotian but also afforest some of the Duotian. In the area of Duotian forests, the radiation is generally 45%-52% lower than that on the farmland, the temperature is 0.8-1 lower than that outside the forest, and the humidity is 3%-5% higher than that of the farmland.

The structure was unique in some positive and constructive way;

Xinghua Duotian Irrigation and Drainage System is a unique irrigation and drainage engineering system for elevated dry farmland in China. Created by the Xinghua people in the long historical development process, it's a unique irrigation project tailored to local natural conditions. In the Ming and Qing dynasties, against the backdrop of frequent floods and gradual silting of the lakes, people dredged rivers for irrigation and turned lakes into farmland by digging out and piling up silt and mud.

With the improvement of water conservancy projects, the river network is increasingly refined, and the water system is controlled by grades: lakes - outer rivers - (water gates) - inner rivers - ponds - ditches - (water gates) – farmland. This is the fruit of the wisdom of the ancient water governance practices in low-lying lands.

The structure bears the stamp of a cultural tradition or a civilization of past;

The history of the Xinghua Duotian Irrigation and Drainage System exceeds 100 years (dating back to the 15th century). The System falls into the category of agriculture drainage structures. Its engineering form remains basically unchanged till today.

The landscape of Duotian has influenced the livelihood of the locals. The so-called “Duotian people” here not only refer to their living habits but also to their knowledge structures and perceptions of life. Within the territory of Duotian, the Lake of Victory, Eight-Diagram Tactics, the Water Margin Port, and the ancient stories of fighting against invasions by the nomadic people which had happened in these reed marshes were the origin of the famous novel Water Margin by Shi Nai’an. Zheng Banqiao, the representative of Yangzhou Eight Eccentrics, was born in Duotian. His unique style of calligraphy is said to be inspired by the cultivated fields of Duotian. The local religious belief has evolved from the primitive worship of water to the worship of its personification and then into the worship of both water gods and heroes with a great contribution to water governance. For example, the local ceremony of “sending the water god down into the river” is said to have the function of predicting the water levels during the flood season of the year.

Engineering utility vis-à-vis designed utility

At the beginning of its establishment, Duotian was protected from floods by its own height, which was about 5 meters. Later on, in order to improve the flood control capacity of the fields, small dikes were built around the fields. The small dikes were connected and transformed into large dikes equipped with water gates for the purpose of water level control both inside and outside the dikes. In this way, the demand for irrigation and flood control could be realized at the same time. After 1949, the government built even larger embankments and drainage pumping stations, solving the regional flooding problem. To make farming easier, the height of Duotian has been reduced to about 1 m.

Present State of Conservation

In recent years, due to fast urbanization, agricultural modernization, rising labour cost and the loss of rural population, the labour-intensive Duotian agriculture has been threatened in aspects such as landscape maintenance, the sustainable utilization of traditional farming techniques, and the maintenance of some engineering facilities.

(1) Part of the System needs to be further repaired and upgraded - In the past few years, the local farmers have implemented very extensive reconstruction of the original Duotian so as to expand the cultivated land area and make farming more convenient. This has unified the size and height of Duotian. The overall System is well preserved, but parts of the System are damaged, resulting in serious siltation and the degradation of the irrigation and water level regulation functions.

(2) The Duotian agricultural ecosystem is shrinking - With the expansion of population and the improvement of living standards, people began to use farmland to build houses, and the village construction expanded into the farmland. Duotian Town is located in a suburb of the city. With the southward and eastward expansion of the city in recent years, the Duotian System has been partly bought for urban and industrial development.

Part of the Hejiaduo Duotian System was used for urban development

(3) The ecosystem of soil and ditches has deteriorated - In recent years, due to the outflow of young labour, the traditional farming practices of desilting the ditches for fertilizers have been gradually abandoned, threatening the sustainability of the traditional farming techniques.

(4) The labour force of Duotian is shrinking and ageing, threatening the sustainability of the heritage - At present, the labour force of the Duotian System is shrinking and ageing, leading to a labour shortage for Duotian farming. Similar to other rural areas, the Duotian region is mainly cultivated by middle-aged and elderly people who are usually less educated and unable to meet the requirements of modernized agriculture.

In order to further protect Duotian, carry forward its traditional farming culture, and promote its sustainability, Jiangsu Province officially issued the Taizhou Duotian Protection Regulations on November 27, 2020, which further clarifies its protection planning protection management, utilization and inheritance.

Management

Duotian Irrigation and Drainage System, as the product of adaptation to local conditions, is a relatively complete irrigation and drainage system with strong sustainability. Its management, especially desilting and embankment enhancement, is both autonomic and coordinated. The traditional way of farming, such as bailing water for irrigation and using silt as fertilizer, has been retained and is still practiced today.