PHILIP M. FEARNSIDE
Sedimentation and flooding in the upper backwater
Sediment deposition at the upper end of the Jirau Reservoir is of particular concern. When water from a river enters a reservoir, the velocity of the water suddenly slows and the largest suspended particles fall to the bottom. At the same time, the larger particles in the bed load (eg coarse sand) stop moving and form sandbanks. Large accumulations of material usually form at the upper ends of reservoirs, even in rivers where the amount of transported solids is only a small fraction of the amount found in the Madeira River. The accumulation of sediments acts as a kind of dam, damming the water in the stretch of river just above the reservoir itself.
Unlike sedimentation within the reservoir itself, which eventually reaches an equilibrium beyond which there is no more sediment accumulation, backwater deposition behind sediment accumulation at the upper end of the reservoir will continue to grow further and further upstream. , thus continually enlarging the backwater (eg, [1]). The backwater will have higher water levels than the river’s natural, causing flooding laterally from the upper backwater. This, for example, is one of the concerns with the Three Gorges Dam in China, where the upper backwater increases flooding in riverine parts of Chongqing, one of the largest cities in the world. [2].
In the case of the Madeira River, the city to be affected is Abunã. The floods would also affect land in Bolivia, located across the river upstream from Abunã, including the Bruna Racua/Frederico Román protected area. Both the EIA [3, 4] and the feasibility study [5, 6] they emphatically state that neither Abunã nor Bolivia will be affected, but they do not take into account any potential effect of expected sedimentation in the upper part of the reservoir.
Simulations with the HEC-6 model indicate substantial sedimentation in the binational stretch of the Madeira River after 50 years, even if the Jirau reservoir were operated at a normal level of 87 m above sea level, or 3 m below sea level. 90m expected for most of the year [7]. This sedimentation would raise the level of the Madeira River bed at the mouth of the Abunã River, thus creating a damming effect that would raise the water levels in the Abunã River as well. The Abunã River is binational, forming part of the border between Brazil and Bolivia. Effects on this river were not included in the feasibility study and EIA/RIMA.
Non-sedimentological impacts
The Madeira River sediment issue, which is the subject of this article, is just one of many controversies surrounding the decision to build dams on the Madeira River and the manner in which the works were licensed. One of the expected impacts of the dams, although not officially recognized, is the loss of a large part of the Madeira River’s fishing production, the most important being the large catfish (especially Brachyplatatystoma rougeauxii and B. vaillantii ) that go upriver each year to spawn at headwaters in Peru and Bolivia [8. 9]. The fishing population depends on the river, including 2,400 members of fishing cooperatives on the Brazilian part of the river alone. [10]. Other impacts include deforestation stimulated by dams, either by the population displaced by the reservoirs or attracted by the works, as well as by agriculture stimulated by planned waterways (e.g., [11, 12]).
Although waterways have been excluded from consideration in environmental impact studies, these dams are central to plans to make the Madeira River and its tributaries navigable for barge traffic. Waterways would be built up to soybean areas in the state of Mato Grosso and much of northern Bolivia. More than 4,000 km of waterways are planned in Bolivia, opening up vast areas of forest for conversion to soy (ie, [13, 14]).
Deforestation and the loss of aquatic and terrestrial habitats from flooding by the reservoirs affect biodiversity in this highly diverse area. [15]. Another concern is the methylation of mercury in anoxic sediments in the tributaries, where many tons of mercury were deposited during the gold mining boom in the 1980s. [16]. Methylation converts metallic mercury into a form that is extremely toxic to humans and other animals.
Both Santo Antônio and Jirau have pending applications for carbon credits under the Kyoto Protocol’s Clean Development Mechanism (CDM). These, like many CDM projects for hydroelectric dams, represent a setback in efforts to combat global warming, because the dams would be built independently of the carbon projects. [17]. The social consequences, in addition to eliminating the main source of livelihood for the local population, include relocating cities and rural residents. There are also urban migration impacts for the construction of the dam, as expected before the start of the work. [18]. There are potential additional impacts on Indigenous Peoples nearby, including several “isolated” groups [19, 20, 21].
GRADES
[1] Morris, GL & Fan, J. 1998. Reservoir Sedimentation Handbook: Design and Management of Dams, Reservoirs, and Watersheds for Sustainable Use. New York, USA: McGraw-Hill.
[2] Luk, SH & Whitney, J. 1990. Unresolved issues: Perspectives from China. In: Ryder, G. (Ed.) Damming the Three Gorges , P. 79-87, Toronto, Canada: Probe International, p. 83-84.
[3] FURNAS, CNO & Leme Engenharia. 2005. EIA- Environmental Impact Study Santo Antônio and Jirau Hydroelectric Power Plants, Rio Madeira-RO. 6315-RT-G90-001. Rio de Janeiro, RJ: FURNAS Centrais Elétricas SA, Construtora Noberto Odebrecht, SA (CNO) & Leme Engenharia. 8 Vol. Volume 1, Vol. 1, p. 7-103. Available in:
[4] FURNAS, CNO & Leme Engenharia. 2006. EIA- Environmental Impact Study Santo Antônio and Jirau Hydroelectric Power Plants, Rio Madeira-RO. Volume E. Complementation and Adaptation to IBAMA’s Requests. Service to Office No. 135/2006 of 02/24/06. 6315-RT-G90-002, Rio de Janeiro, RJ: FURNAS Centrais Elétricas SA, Construtora Noberto Odebrecht, SA (CNO), Leme Engenharia. 3 Vol., Vol. 1, p. 13. Available at:
[5] PCE, FURNAS & CNO. 2004. Madeira River Hydroelectric Complex: Feasibility Studies for AHE Jirau. Case No. PJ-0519-V1-00-RL-0001. Rio de Janeiro, RJ: Projetos e Consultoria de Engenharia Ltda. (PCE), Furnas Centrais Elétricas SA (FURNAS) & Construtora Noberto Odebrecht, SA (CNO). 4 vol. + annexes, Volume 1, Vol. 1, p. 1.6 & 7-103. Available in:
[6] PCE, FURNAS & CNO. 2005. Madeira River Hydroelectric Complex: Feasibility Studies for AHE Santo Antônio. Case No. 48500.000103/03-91. Final Report PJ-0532-V1-00-RL-0001. Rio de Janeiro, RJ: Projetos e Consultoria de Engenharia Ltda. (PCE), FURNAS Centrais Elétricas SA & Construtora Noberto Odebrecht, SA (CNO). 4 vol. + annexes, Tome A, Vol. 7, p. VII-15-16. Available in:
[7] PCE. 2007. Sedimentological Studies of the Madeira River . Rio de Janeiro, RJ: Projetos e Consultoria de Engenharia Ltda. (PCE).
[8] Barthem, R. & Goulding, M. 1997.The Catfish Connection: Ecology, Migration, and Conservation of Amazon Predators . New York, USA: Columbia University Press.
[9] Fearnside, PM 2009. Fisheries Resources. In Val, AL & dos Santos, GM (Eds.) Amazon Strategic Study Group (GEEA) Tomo II, Manaus, AM: National Institute for Amazon Research (INPA). P. 38-39.
[10] Ortiz, L., Switkes, G., Ferreira, I., Verdum, R. & Pimentel, G. 2007. The largest tributary of the Amazon River threatened: Hydroelectric plants on the Madeira River . São Paulo, SP: Friends of the Earth-Brazil & Ecology and Action (Ecoa). Available in:
[11] Vera-Diaz, MC, Reid, J., Soares-Filho, B., Kaufmann, R. & Fleck, L. 2007. Effects of energy and transport infrastructure projects on soy expansion in the Madeira River basin. Conservation Strategy Fund, CSFSeries no. 7. Lagoa Santa, MG: Conservation Strategy Fund. Available in:
[12] Escada, MIS, Maurano, LE & da Silva, JHG 2013. Dynamics of deforestation in the area of influence of the hydroelectric plants of the Madeira River Complex, RO. In: JR dos Santos (Ed.)XVI Brazilian Symposium on Remote Sensing, Foz do Iguaçu , Brazil 2013 . São José dos Campos, São Paulo: National Institute for Space Research (INPE). P. 7499-7507.
[13] PCE, FURNAS & CNO.2002. Madeira river hydroelectric inventory: Porto Velho – Abunã stretch. Case No. 48500.000291/01-31. Final Report: MAD-INV-00-01-RT . Rio de Janeiro, RJ: Projetos e Consultoria de Engenharia Ltda. (PCE), Furnas Centrais Elétricas SA (FURNAS) & Construtora Noberto Odebrecht SA (CNO). Available in:
[14] Killeen, TJ 2007. A perfect storm in the Amazon wilderness: Development and conservation in the context of the initiative for the Integration of the Regional Infrastructure of South America (IIRSA) . Arlington, Virginia, USA: Conservation International. Available in:
[15] Fearnside, PM 2006. Consultants’ opinions on the environmental impact study of the project for the Santo Antônio and Jirau hydroelectric development, Rio Madeira-RO. Technical Opinion on ecosystems. In: Technical Opinions from Sector Specialists—Physical/Biotic Aspects. Content Analysis Report of the Environmental Impact Studies (EIA) and the Environmental Impact Report (RIMA) of the Santo Antônio and Jirau Hydroelectric Power Plants on the Madeira River, State of Rondônia. Porto Velho, RO: Public Ministry of the State of Rondônia, 2 Vols. Part B, Volume 1, Opinion 8, p. 1-15.
[16] Forsberg, BR & Kemenes, A. 2006. Technical opinion on hydrobiogeochemical studies, with specific attention to the dynamics of Mercury (Hg). in Technical opinions from sector experts—physical/biotic aspects. Content analysis report of the Environmental Impact Studies (EIA) and the Environmental Impact Report (RIMA) of the Santo Antônio and Jirau hydroelectric plants on the Madeira River, Rondônia state. Porto Velho, RO: Public Ministry of the State of Rondônia. 2 Vol. Part B, Vol. I, Opinion 2, p. 1-32. Available in:
[17] Fearnside, PM 2013. Carbon credit for hydroelectric dams as a source of greenhouse-gas emissions: The example of Brazil’s Teles Pires dam. Mitigation and Adaptation Strategies for Global Change 18(5): 691-699. doi: 10.1007/s11027-012-9382-6
[18] Polis Institute. 2006. Opinion on the Role of the Municipality of Porto Velho in the face of Urban Impacts and the Environmental Impact Study of the Madeira River Hydroelectric Power Plant Project. São Paulo, SP: Instituto Pólis. Available in:
[19] Algayer, A., Vaz, A. & Silveira, E. 2008. Activities planned for regions where there are references to isolated Indians who will be influenced by the Santo Antônio HPP. July 14, 2008. Brasília, DF, Brazil: Assistance Directorate, General Coordination of Isolated Indians (CGII), National Indian Foundation.
[20] Zagallo, JGC & Lisbon, MV 2011. Human Rights Violations at the Madeira River Dams: Preliminary Monitoring Mission Report. São Paulo, SP: National Rapporteurship for the Human Right to the Environment, Brazilian Platform for Economic, Social, Cultural and Environmental Human Rights (Dhesca Platform). Available in:
[21] This text is a partial translation of Fearnside, PM 2013. Decision-making on Amazon dams: Politics trumps uncertainty in the Madeira River sediments controversy. Water Alternatives 6(2): 313-325. The author’s research is funded by the National Council for Scientific and Technological Development (CNPq) (proc. 304020/2010-9; 573810/2008-7), by the Fundação de Amparo à Pesquisa do Estado do Amazonas (FAPEAM) (proc. 708565). ) and the National Institute for Research in the Amazon (INPA) (PRJ1).
Philip Fearnside is a researcher at the National Institute for Research in the Amazon (Inpa), in Manaus, at CNPq and a member of the Brazilian Academy of Sciences. He also coordinates the INCT (National Institute of Science and Technology) of the Environmental Services of the Amazon. In 2007, he was one of the scientists awarded the Nobel Peace Prize by the Intergovernmental Panel on Climate Change (IPCC).
