Environmental Consequences of Damming the Mainstream Lancang-Mekong River: a Review
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Earth-Science Reviews 146 (2015) 77–91 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Environmental consequences of damming the mainstream Lancang-Mekong River: A review Hui Fan a,b,⁎,DamingHea,b,HailongWangc a Asian International Rivers Center of Yunnan University, Kunming 650091, China b Yunnan Key Laboratory of International Rivers and Transboundary Eco-Security, Kunming 650091, China c Huaneng Lancang River Hydropower Company Ltd., Kunming 650214, China article info abstract Article history: Damming rivers to generate hydropower can help mitigate the world's energy crisis and reduce the risk of global Received 12 July 2014 climate change; however, damming can also produce enormous negative effects on the environment and ecosys- Accepted 27 March 2015 tems. The mainstream Lancang-Mekong River within China has been planned as one of the thirteen state hydro- Available online 3 April 2015 power bases. To date, there have been six operational dams along the mainstream Lancang River, and the 15 remaining dams of the proposed Lancang cascade will be completed in the next decades. In this paper, we exam- Keywords: ined several crucial environmental changes and ecological responses that have resulted from the construction Dam construction Environmental impacts and operation of the existing dams of the Lancang cascade. The current literature and observational data suggest Ecosystem responses that the commissioned dams have led to a decline in the flood season water discharge and annual sediment flux Lancang cascade dams within China's borders, reservoir aggradations, and water quality degradation in the reservoirs, which has nega- Mekong River tively affected riverine aquatic biological communities and fish assemblages. In contrast, the dams have only had Transboundary waterway small unfavorable effects on downstream environments and ecosystems outside of China. Because of the poten- tial environmental and geopolitical risks of the Lancang cascade dams, a long-term basin-wide terrestrial and aquatic monitoring program is urgently required to ensure that regional sustainable development occurs in the Lancang-Mekong River Basin. © 2015 Elsevier B.V. All rights reserved. Contents 1. Introduction............................................................... 77 2. ProfileoftheLancangcascadedams.................................................... 78 3. Post-damenvironmentalconsequences................................................... 80 3.1. Hydrologicaleffects........................................................ 80 3.2. Upstreamreservoirsiltationanddownstreamsedimentdischargedecline................................ 80 3.3. Changesinwaterquality...................................................... 83 4. Ecologicalconsequencesofdam-triggeredenvironmentalchanges....................................... 84 4.1. Responsesofphytoplanktonandzooplankton............................................. 84 4.2. Responsesofthezoobenthos.................................................... 86 4.3. Responses of fishresources..................................................... 88 5. Concludingremarks............................................................ 89 Acknowledgments............................................................... 89 References.................................................................. 89 1. Introduction Climate change is one of the greatest challenges of the 21st century (IPCC, 2011), and mitigating rising global surface temperatures requires ⁎ Corresponding author at: Asian International Rivers Center of Yunnan University, No.2 North Cuihu Road, Kunming, Yunnan 650091, China. Tel./fax: +86 871 65034577. additional renewable energy sources to satisfy the increasingly high pri- E-mail address: [email protected] (H. Fan). mary energy demand, which is driven by the global population and http://dx.doi.org/10.1016/j.earscirev.2015.03.007 0012-8252/© 2015 Elsevier B.V. All rights reserved. 78 H. Fan et al. / Earth-Science Reviews 146 (2015) 77–91 economic growth. As the second largest renewable energy vector and respectively, is underway (Yuan, 2010). Of the planned cascade dams largest source of renewable energy in the electricity sector, hydropower along the mainstream Lancang River, there are currently six large has a significant potential to reduce anthropogenic greenhouse gas commissioned dams: the Manwan, Dachaoshan, Jinhong, Xiaowan, emissions. In 2012, hydropower was estimated to account for approxi- Gongguoqiao, and Nuozhadu dams, with the Nuozhadu completed in mately 3.8% of the world's primary energy use and contribute approxi- 2013. According to the hydropower development plan proposed by mately 16.5% to the global electricity supply (REN21, 2014; Spänhoff, the Huaneng Lancang River Hydropower Company (also known as 2014). By the end of 2013, the total global installed hydropower capac- Hydrolancang), the remaining 8 dams of the planned cascade in the ity increased to 1000 GW, producing an annual power generation of Yunnan section of the Lancang River will be nearly operational by 3750 TWh (REN21, 2014). However, the total worldwide technical hy- 2016, and the hydropower installed capacity in the Lancang mainstream dropower potential and annual average energy generation are estimat- will total 30.0 GW by 2020 (Yuan, 2010). Several problems, such as land ed at 3721 GW and 14 576 TWh, respectively, which are roughly four inundation (He et al., 2004), hydrologic regime alteration (He et al., times the current hydropower capacity and generation (IPCC, 2011; 2006; Lu and Siew, 2006), sediment trapping (Fu and He, 2007; REN21, 2014). Of the total technical potential for hydropower, the unex- Kummu and Varis, 2007; Fu et al., 2008a,b; Kummu et al., 2010), ploited capacity varies from approximately 47% in Europe and North reservoir-triggered seismicity (Li et al., 2004, 2012), geological instabil- America to 92% in Africa (IPCC, 2011; REN21, 2014). This indicates ity (He et al., 2004), habitat fragmentation (Yi et al., 2014), and resettle- that there are large-scale opportunities for continued hydropower de- ment (Wang et al., 2013), have emerged with the unprecedented velopment worldwide, with the largest development potentials in advancement of extensive hydropower development. In particular, the Africa, Asia and Latin America. Lancang-Mekong River is one of the largest Asian international rivers China is a rapidly developing country with heavy energy consump- and a hot spot for biodiversity, and it links China with five downstream tion. Although China is ranked first in the world in terms of both total Southeast Asian countries: Myanmar, Laos, Cambodia, Thailand and installed hydropower capacity and generation, the share of its hydro- Vietnam; thus, the river has extremely high ecological, economic power towards the total electricity production and the development and sociological importance. Although only a small fraction of the level of its hydropower are relatively low (Huang and Yan, 2009). By Lancang-Mekong's discharge is input to the South China Sea from the the end of 2013, China's installed hydropower capacity and energy gen- upstream Chinese catchment, the downstream transboundary potential eration totaled 280 GW and 896.3 TWh, respectively, accounting for ap- impacts of hydropower development have attracted much attention proximately 22.4% and 16.8%, respectively, of China's total (Hu, 2014). since China planned the Lancang dam cascade along the middle and The share of hydropower in the total electricity production is only lower sections of the Lancang River. Hydrological effects with respect 17.2%, which is much less than the shares of 96.6%, 83.7% and 57.9% in to reservoir filling and water release have been maliciously exaggerated Norway, Brazil and Canada, respectively (Huang and Yan, 2009). To because of the scarcity of reliable data and knowledge (Lu and Siew, meet its goal of cutting carbon dioxide emissions per unit of gross do- 2006; Campbell, 2007; Adamson et al., 2009; Lu et al., 2014). This mestic product (GDP) by 40–45% before 2020, China will have to in- poses the most important threat to strengthening the geopolitical and crease its efforts to develop hydropower. Therefore, China announced economic cooperation in the Greater Mekong Subregion (GMS). To to mainly construct eight of the 13 planned hydropower bases eliminate much of the apprehension and discontent over the potentially (i.e., Jinsha River, Lancang River, Dadu River, Upper Huanghe River, Ya- adverse impacts of extensive hydropower development on the local and long River, Nu River, mainstream Changjiang River, and Middle Yarlung downstream environment, the environmental consequences of the Zangbo River) during the Twelfth Five-Year period (2011–2015) and commissioned dams along the Lancang mainstream must be examined further expand its installed conventional hydropower capacity to in detail. Therefore, the present study aims to provide a comprehensive 420 GW by 2020, which includes the current conventional hydropower overview of the environmental effects of damming in the mid-lower of 350 GW (CNEA and CNREC, 2012). This plan explicitly listed the mainstream of the Lancang River, and the planning and construction 60 key hydropower projects during the Twelfth Five-Year period, 13 of dams along the mainstream Lancang River are introduced first. We of which will be built along the mainstream Lancang River (CNEA and then analyze the environmental effects of the Lancang