Water 2015, 7, 2349-2357; doi:10.3390/w7052349 OPEN ACCESS water ISSN 2073-4441 www.mdpi.com/journal/water Opinion China’s Policy on Dams at the Crossroads: Removal or Further Construction? Chiyuan Miao 1,2,*, Alistair G. L. Borthwick 3, Honghu Liu 1 and Jigen Liu 1 1 Changjiang River Scientific Research Institute, Changjiang Water Resources Commission, Wuhan 430010, Hubei, China; E-Mails: [email protected] (H.L.); [email protected] (J.L.) 2 State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China 3 School of Engineering, The University of Edinburgh, The King’s Buildings, Edinburgh EH9 3JL, UK; E-Mail: [email protected] * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel./Fax: +86-10-5880-4191. Academic Editor: Sharon Megdal Received: 2 December 2014 / Accepted: 12 May 2015 / Published: 19 May 2015 Abstract: During the past century, the number and scale of reservoirs worldwide has grown substantially to meet the demand for water and hydropower arising from increased population, industrialization, and urbanization. This is particularly the case in China, where reservoir construction increased rapidly after the Chinese economic reform and the introduction of open-door policies. On average, 4.4 large reservoirs with a capacity greater than 0.1 km3 were constructed per annum during the 1970s–1990s. This average reached 11.8 such reservoirs per annum in the 2000s. Considering the adverse impact of dams on rivers and riparian communities, various environmentalists and non-governmental organizations in China have begun to protest against the construction of dams. Now China’s policy on dams is at a crossroads: Removal or further construction? In this paper, we systematically assess the construction of reservoirs in China and discuss the benefits and drawbacks of large-scale reservoir projects on several major rivers in China: The Yangtze River, the Yellow River and the Mekong River. Lastly, we provide a perspective on the future of reservoir development in China, taking into account natural conditions, renewable hydropower resources, and greenhouse gas emissions. Keywords: reservoir; natural resource; eco-environment; China Water 2015, 7 2350 1. Introduction During the past century, the number and scale of reservoirs worldwide has grown substantially to meet the demand for water and hydropower arising from increased population, industrialization and urbanization. It is reported that an average of two dams with heights exceeding 15 m were completed each day throughout the latter half of the 20th Century [1]. To date, over 50,000 such dams have been constructed globally, contributing to a total storage capacity of more than 8300 km3 [2]. At present, more than 60% of the world’s rivers are dammed. According to the latest Global Reservoir and Dam (GRanD) database [3], the total capacities, by country, of the largest reservoirs capacity (>0.1 km3) are: Canada (860.7 km3), Russia (811.8 km3), USA (767.5 km3), Brazil (530.3 km3), and China (451.0 km3). China currently has the largest agricultural economy in the world, as well as the largest population. Dams and reservoirs have played an important role in the recent socio-economic development of China, especially since the Chinese economic reform and the introduction of open-door policies in the late 1970s. Statistics show that reservoir construction in China developed rapidly over the past 30 years. For example, an average of 4.4 large reservoirs (of capacity greater than 0.1 km3) were constructed per annum during the 1970s–1990s (Figure 1). The pace of construction accelerated after 2000, with an average of 11.8 large reservoirs constructed each year during the 2000s. By 2011, China possessed 552 large capacity (>0.1 km3) reservoirs, 3269 medium capacity (0.01–0.1 km3) reservoirs, and 84,052 small capacity (0.0001–0.01 km3) reservoirs—with a total storage volume of 692.4 km3 [4]. The total capacity grew at a rate of 4.43 km3 per annum between 1973 and 1999, and the rate increased to 20.63 km3 per annum after 2000 (Figure 1). Although almost all the rivers in China are now regulated by reservoirs, China still has considerable capacity for further exploitation of its residual water resources. According to the China Water Resources Bulletins from 2006 to 2010, on average about 22.34% of the total available water resources in China were being exploited and utilized. There are very significant differences among the river basins: The northern basins have >50% utilization and the Haihe river basin has even reached >90% utilization. (a) (b) Figure 1. Distribution of dams throughout China in 2011 (a); and growth in the number of large reservoirs and the total capacity of reservoirs in China over the past 30 years (b). Water 2015, 7 2351 2. Negative Impacts from Reservoir Development Reservoirs provide considerable socio-economic benefits by increasing the water supply available for municipal, industrial, and agricultural uses, controlling floods, and generating hydropower. At the same time, reservoirs also cause severe negative impacts, including biodiversity depletion, ecosystem degradation, and population displacement, etc. Illustrative examples are provided by the large-scale reservoir projects on the Yangtze River, the Yellow River, and the Mekong River in China. The Three Gorges Reservoir (TGR) on the Yangtze River is the largest river regulation and hydroelectric power station in the world [5]. It cost more than US $32 billion to construct and has an operational water level 110 m above the downstream river level. The TGR has a water surface area of 1080 km2, and the Three Gorges Dam controls a watershed area of over 1 million km2. The TGR has involved resettlement of more than 1.2 million local residents whose original habitations were located below the post-TGR upper water level. Although China has spent more than US $6.3 billion on resettlement programs [6], complicated social challenges have arisen in helping the resettled former residents to adapt successfully to their new surroundings [7]. Water retained in the TGR has submerged an estimated 1300 sites of cultural and archaeological interest [8]. Construction of dams along the Yangtze River has impeded the spawning migration of certain fish species, leading to considerable reductions in the numbers of Chinese sturgeon (Acipenser sinensis) and Dabry’s sturgeon (Acipenser dabryanus), and the possible extinction of the Chinese paddlefish (Psephurus gladius) [9]. Following the 156 m impoundment in 2007, the phytoplankton diversity index was observed to have decreased from 85.52% to 32.32% in tributaries in the TGR region. River flow in the Yangtze is generally slower than it was, leading to decreased scour of the river banks and blooms of toxic algae in tributaries. The vast area covered by the TGR has encouraged the spread of Oncomelania snails, which carry the parasitic disease schistosomiasis [10]. Another drawback of the TGR arises from its sheer scale—The immense hydrostatic loading created by the water behind the dam may induce seismic activity and the raised water level may result in landslides and erosional processes [11]. The potential risk of dam failure must also be considered because this would affect more than 70 million people living downstream. The dams also impaired the natural habitats of the now-extinct Chinese river dolphin Lipotes vexillifer [12]. The second example is provided by the cascade of more than 25 hydraulic projects along the Yellow River, with a total reservoir volume exceeding 55.75 km3. The Yellow River is the second largest river in China and contributes about 6% of global river sediment load [13]. Surface water evaporation from the upper and middle mainstream reaches of the Yellow River increased by approximately 68% after the construction of these reservoirs, resulting in a corresponding 2.3% decrease in water discharge [14]. The reservoirs in the Yellow River regulate both water discharge and sediment load, and control the amount of sediment deposited in the downstream channel. In the past, especially from the 1970s to the end of the 1990s, low flows in the lower Yellow River led to increased deposition that elevated the riverbed, prolonging the periods during which the river dried up. At Lijin, near the mouth of the river, no discharge was recorded for a total of 226 days in 1997 [15], which hastened the formation of the so-called ‘suspended river’ [11]. Moreover, the increased deposition aggravated the risk of major floods occurring in a river that has a long history of flood disasters. The cascade of reservoirs has greatly improved the water-sediment situation in the Yellow River: the occurrence of zero flow events has been reduced in recent years and the riverbed is no longer significantly rising. Consequently, most of Water 2015, 7 2352 reservoirs are gradually silting up, even after regular flushing. Furthermore, the barriers created by the dams have resulted in reductions in the numbers of certain indigenous species of semi-migratory fish [16]. It has been reported that about 13 fish species in the Yellow River are already almost extinct, including Cultrichthys erythropterus, Leiocassis crassilabris, Oryzias latipes, and Mastacembelus aculeatus [17]. The final and perhaps most contentious example is the dam cascade under construction along the Mekong River. For this case, we consider the river basin as a whole, rather than focusing solely on the upper reach in China. The Mekong River rises in Tibet and flows for 4800 km before eventually discharging into the Gulf of Thailand. The Mekong River Basin occupies a total area of 795,000 km2 and overlaps parts of China, Myanmar, Thailand, Laos, Cambodia, and Vietnam, and has a mean discharge rate of about 14,500 m3/s.