A historical perspective of river basin management in the Pearl River Delta of China
Introduction
The Pearl River (“Zhujiang” in Chinese) Delta, China, is located between latitudes 21°40′N and 23°N, and longitudes 112°E and 113°20′E (Fig. 1). It is the third largest river delta in the nation (next to the Yangtze and Yellow River Deltas), with an area of 17,200 km2. The delta has a subtropical climate with an average annual temperature between 21 and 23 °C, and an average precipitation from 1600 to 2600 mm. Because of the impact of the East Asian Moonsoonal circulation, about 80% of the rainfall comes in the period of April–September with a concentration in the months of May–July, when flooding is prone to occur (Ditu Chubanshe, 1977). Another hazard is typhoons, which occur most frequently from June to October. Since 1978, when the economic reform and open-door policy was implemented, a dramatic social, economic, and spatial transformation has occurred in China. This is particularly true in the coastal regions such as the Pearl River Delta, where economic growth has exhibited a two-digit rate over the past two decades and which has appeared as one of the most advanced regions in the nation (Xu and Li, 1990; Lin, 1997; Weng, 1998). The urbanization process has been speeded up due to accelerated economic development. Massive parcels of agricultural land are disappearing each year for urban or related uses. Because of the lack of appropriate land use planning and measures for sustainable development, rampant urban growth has created severe environmental consequences (Weng, 2001a, Weng, 2001b, Weng, 2002). The field surveys the author conducted in the summers of 1998 and 2001, sponsored by the National Geographic Society, witnessed the deteriorating environment. Fieldworks were carried out in different parts of the delta to provide “ground truth” data on current land use and land cover, and first-hand data on environmental changes induced by urbanization. Interviews with city planning officers, visits to contaminated sites, and literature and document surveys were also conducted.
Nothing was more important than water in shaping the civilization in the delta over the past 2000 years. The fertile alluvial deposits, the subtropical climate, and millenniums of exploitation have nurtured the region into one of the most diversified agricultural areas in China. Its paddy cultivation, sugarcane and fruit horticulture, and dike–pond agriculture–aquaculture have long been known to the nation and to the world. Innovations in water and soil conservation technology were crucial to these agricultural accomplishments. Recent environmental, socioeconomic, and demographic changes in the delta region urge us to re-examine the significance of these technological innovations from a historical perspective, in order to understand better the emerging relationship between the people and the environment.
The objective of this paper is to examine the history of the formation and development of three water and soil conservancy technologies, namely, dike building, land reclamation, and dike–pond systems, and their impacts on the delta's evolution in the Holocene period. Field survey data were applied in addition to the literature and documents in government gazetteers (di fang zhi), archeological discovery, agricultural history, geology, and geography. These data and materials were analyzed to demonstrate that the innovation of dike building, land reclamation, and dike–pond agriculture–aquaculture systems was a result of the dynamics of people and the environment and their interplay in the Holocene era. A major argument is that these water and soil conservation technologies were elegant in that they showed a great understanding of the people–environment interactions, and provided a good lesson for today's water resources and river basin management in the delta as well as in other areas of similar settings in the world.
Section snippets
The geomorphological setting and drainage system
Geomorphologically, the delta consists of three subdeltas: the West River (Xijiang in Chinese), North River (Beijiang in Chinese), and East River (Dongjiang in Chinese) Deltas. These subdeltas were formed by sediments, which originated approximately 40 thousand years ago (Department of Geography, Zhongshan University, 1988). There are hills surrounding the delta to the east, west, and north that have an average of 500 m above mean sea level (m.s.l.). Inside the delta itself, there are over 160
Increased flooding and dike building
Agricultural development in the delta region was strongly associated with dike building technology. The dikes were initially built to prevent low-lying lands from being flooded. Excess water could be drained from the enclosed fields by using waterwheels (for example), thus improving water conservancy and agricultural productivity. The first dike was built during the Tang Dynasty (Zeng and Huang, 1987), in response to a sharp increase in flood frequency. Statistics of flood frequency during
History of land reclamation
Sandy fields, located between the coast and the inland, are a special type of farmland that was reclaimed from sea beaches or river marshes. In the West and North River Deltas, sandy fields are distributed near the line linking Huangpu, Shiqiao, Longjiang, and Jiangmen. The formation of sandy fields is closely related to two factors: the extension of the delta by the deposition of sediments, and the development of land reclamation technology.
From the Ming to Qing Dynasties, the delta region
Origin and development of the dike–pond landscape
In the low-lying central delta, there were originally numerous waterways, and flooding and tide disasters were frequent. Waterways began to silt up one after another since dikes were built in the Tang and Song Dynasties. Silt from the upper reaches can only be deposited outside the dikes and the cofferdams. In time, a unique landscape was created, where the fields inside dikes and cofferdams were lower than the water surface of rivers outside the dikes and cofferdams. When a flood, a torrential
Discussion
While the Pearl River Delta appeared as one of the most rapidly advanced economic regions in the nation after 1978 and has now become known as the world's workshop, a series of environmental problems have emerged, including continued shrinkage of agricultural land, upstream deforestation and soil erosion, silting up of river channels, flooding, and the decline of water surface in the estuaries. Although it is one of the wettest regions, water crises have occurred in such cities as Guangzhou,
Conclusions
Water is one of the most important natural forces that have shaped the material cultural landscapes of the Pearl River Delta. The changing relationships between people and the physical environment have led to innovations in water and soil conservation technology. Three innovations in water and soil conservancy, i.e., dike building, land reclamation, and dike–pond systems, have been examined in this paper from a historical perspective. These technologies were found to best reflect local farmers’
Acknowledgement
The authors thank the National Geographic Society for providing a grant (Grant no.: 6811-00) to sponsor this research. The constructive comments and suggestions of three anonymous reviewers are greatly acknowledged to help improving this paper.
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