Abstract: China is home to roughly half the world’s large dams and probably a similar fraction of smaller ones. These structures alter the flow of thousands of the country’s rivers, creating hydroelectricity, providing irrigation and flood control, and flattening stretches of river that would otherwise be unnavigable. Yet dams are controversial: they can bring significant and often irreversible changes to ecosystems and human communities, from sediment trapping to human resettlement, tarnishing their image as green technology.
Citation: Brown (2022). Berkshire Encyclopedia of China. Great Barrington, MA: Berkshire Publishing.
Keywords: dams; hydropower; hydroelectricity; water; rivers; flood control; navigation; renewable energy; resettlement; sedimentation; fish
Any figures or illustrations or illustrations included here are not finalized for publication. Advance publication date as per post date. Copyright Berkshire Publishing Group.
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Dams (Dàbà 大坝, Shuǐbà 水坝)
In 1949, China had just a handful of large dams. Now, more than seventy years later, it boasts roughly half the world’s large dams; the World Commission on Dams (2000) estimated that more than 20,000 great walls of earth, rock, and concrete punctuated the country’s river systems at the turn of the twenty-first century. China’s official figures for large dams are more modest at around 5,000, a discrepancy likely arising from different ways of classifying a dam’s size—by height, reservoir volume, or installed power-generating capacity. Whatever the exact figure, China’s National Bureau of Statistics (2017) reports a staggering 98,795 reservoirs, all of which are, by definition, impounded by a dam or weir of some sort.
China’s dams have brought benefits such as irrigation to arid regions, flood control to cities in downstream floodplains, and hydroelectricity at scales from single households to entire regions. Yet those same dams and their reservoirs can displace and fragment human communities, destroy riparian and aquatic habitats, alter water flow and sediment transport patterns, and even increase the likelihood of tectonic events such as earthquakes. Moreover, as massive, complex, and expensive projects involving a wide array of contractors, they can be easy targets for unscrupulous officials who would siphon public funds into private pockets. As a result, China’s dams remain highly controversial for their social and ecological costs.
That China should be the world’s most dammed country is not surprising considering its size, topography, number of rivers, and wide seasonal and geographic variability of water resources. The Ministry of Water Resources and National Bureau of Statistics (2013) report some 22,000 Chinese rivers with watersheds larger than 100 square kilometers, and over 200 rivers with watersheds 100 times that size. Major rivers originating at elevations greater than 4,000 meters on the Tibetan Plateau, such as the Chang (Yangzi), Huang (Yellow), Lancang (Mekong), and Nu (Salween) give rise to much of the country’s tremendous hydroelectric potential as they flow eastward and southward. That potential, more than 500 Gigawatts (GW), far surpasses that of any other country; indeed, the installed hydropower in Yunnan Province alone already exceeds that of entire countries such as Russia, India, Norway, and Switzerland with substantial hydropower assets (Hennig et al. 2016). Yet those same rivers also bring seasonal flooding that can devastate farmland and destroy cities, especially since many of the forests in their headwaters—forests that would normally help hold rainfall in the soil and soil on the slopes—were severely degraded during the Maoist period (Shapiro 2001) and still face significant pressures, despite some evidence of slowed deforestation rates (Song et al. 2018).
Throughout most of the reform period, China’s economy and demand for electricity have grown in lock step with each other. So, too, have the justifications for building dams. Proponents of hydroelectric dams have gained even more traction in recent years as concerns about air pollution and climate impacts, stemming largely from China’s coal-fired economic development, have intensified. Most dams in China, especially the large ones, are designed to serve multiple purposes, with hydropower generation and flood control taking priority. They are also frequently constructed in cascades—one dam after another along the same river for hundreds of kilometers. Since a river’s hydropower potential depends solely on the gradient (steepness) of its channel and the volume of its flow, a cascade system can take advantage of the river’s continual ability to generate electricity for its entire journey from source to mouth, but also seriously alters the flow characteristics, sediment transport capabilities, and habitats of the river.
The Three Gorges Dam on the Yangzi River, completed in 2010, is a household name and a world record-holder, with its 600-km-long reservoir, 2-km-wide main dam structure, and 22.5 Gigawatts of installed hydroelectric capacity. Yet dozens of other megadams, a class in which China has an outsized presence, are outliers in their own right. The 1570-Megawatt (MW) Manwan Dam, completed in the mid-1990s, was the first dam on the main stream of the transboundary Mekong River, widely seen as the lifeblood of mainland Southeast Asia. Just upstream on the same river, the 4,200-MW Xiaowan Dam, completed in 2002, was the highest concrete arch dam in the world at 292 meters for a short decade until it was dwarfed by the 305-meter Jinping Dam on the Yarlung River. These two dams belong to two of several massive cascades planned or underway on the Lancang, Chang, Nu, and other western rivers, even as China’s supply of hydropower seems to be outstripping demand (Magee and Hennig 2017), a trend that will likely hold for some time if global economic growth stagnates.
The Three Gorges made international headlines for its displacement of more than a million people, yet dams and cascades all over the country have led to the displacement of tens of millions of people in the last half-century. If allowed to proceed, even the Nu River cascade, in a remote and sparsely populated border region of southwestern China, would displace roughly fifty-thousand, many of whom are members of ethnic minority groups particularly vulnerable to socioeconomic distress when their communities are disrupted and resettled (Brown, Magee, and Xu 2008). And even though compensation schemes for resettled communities have improved, much work remains to be done to ensure that those who are resettled have the resources needed to thrive in their new homes (Tilt 2015).
Water—and the control of “unruly” waters through hydraulic projects and engineering ingenuity—is far from only a twentieth-century priority in China. Indeed, it is woven into China’s creation mythology, most clearly through the legend of the Great Yu (Dà Yǔ zhìshuǐ, 大禹治水), who famously tamed the flood-prone Yellow River around 2100 bce through dredging, levees, and irrigation canals. Now, its national identity and reputation for hydraulic projects cemented, China has in recent years become a significant exporter of dam construction, technology, finance, and expertise around the globe. Consortia of Chinese companies, most of them subsidiaries of major state-owned enterprises (SOEs) such as Sinohydro, China Three Gorges Corporation, and Hydrolancang, have undertaken dam projects in Southeast Asia, Africa, and Latin America. Each will bring its own set of socioeconomic, biophysical, and geopolitical tradeoffs.