Madeira-Sediments 4 river dams: Expert opinion and official scenarios

CMIO 19 de May de 2014

5 minutes read

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PHILIP M. FEARNSIDE

The high uncertainty about sediments and their impacts is indicated by the opinions of a number of experts who have examined the different reports. Carlos Tucci [1], in a consultancy report commissioned by IBAMA, found the results of the HEC-6 model in the EIA/RIMA to be “inconsistent”. For example, the model gives the “strange” result indicating that some stretches of the river to be flooded by the Santo Antônio reservoir would have more sedimentation in the undammed river than with the reservoir. [2]. He also considered “apparently arbitrary” a downward adjustment of 30% that the EIA/RIMA applied to the model output for sedimentation. [2]. He concluded that further studies of the sediments were needed and called for the formation of an international panel of experts to examine the problem. [1].

José Tundisi and Takako Matsumura-Tundisi [3], in an opinion for the Public Ministry of the State of Rondônia, drew attention to the inconsistency between the different estimates of suspended sediments versus the bed load of the Madeira River and the dependence of the EIA/RIMA conclusions on the single value that the authors of this document chose to use: All the sedimentation calculation performed by the designers is based on the proportion of 95% suspended load to 5% in the river bed”. Tundisi and Matsumura-Tundisi pointed out several factors that can increase sediment and asked for information on sediment sources across the basin upstream of the dams. Later, Jose Tundisi [4] endorsed Alam’s Brune curve analysis indicating that there would be no sediment accumulation [5].

Jorge Molina Carpio [6] criticized the report by consultant Alam [7] for having assumed that the Madeira River has a flow of more than 40,000 m³/s for 1.5 to 2 months per year [8]allowing sediments up to 3 mm in diameter to be taken from the reservoir [9]. However, Molina Carpio [6] pointed out that flows at this rate last, on average, only 1.5 weeks per year, and that these large flows are often absent for periods of several years, meaning that sediment would accumulate in the reservoir beyond the amount at which the brief peaks in flow could remove.

In March 2007, a review of the flow data substantially reduced the estimate of the frequency of occurrence of very high average monthly flows. [10]. Alam later claimed that a flow of just 18,000 m³/s would be enough to expel the sediments [11]. However, at 18,000 m³/s, only particles up to 0.5 mm in diameter would be transported through the reservoir [12].

Thomas Dunne [13]in an opinion for the NGO Rios Internacionales, stated that the Brune curve that Alam [7] used to conclude that reservoirs will not accumulate sediment on an annual basis is less adequate than the simulations of sediment movement done with the HEC-6 model, which were the basis for the conclusions of the feasibility study and EIA/RIMA.

Dunne also pointed out the high degree of uncertainty in information about the sizes of sediment particles, especially the percentage of sand in the suspended load, as well as the lack of information about sampling methods (e.g., measurements with an average for the vertical profile vs. a calculation from surface samples). He also emphasized the lack of an uncertainty analysis. Furthermore, with respect to Alam’s conclusion that all sediment accumulated during low flow periods will be carried away by peak flows, Dunne [13] states that “it is simply not adequate to make qualitative judgments about the net effect on sediment accumulation of many low-flow days and fewer high-flow days” [14].

GRADES

[1] Tucci, CEM 2007. Analysis of environmental studies of the Madeira River projects. February 2007, Report to the Brazilian Institute for the Environment and Renewable Natural Resources (IBAMA), Brasília, DF, p. 15. Available at:

[2] Op. cit. Note [1] (Tucci, 2007): p. 11.

[3] Tundisi, JG & Matsumura-Tundisi, T. 2006. Technical Opinion on Limnology, Water Quality and Sedimentology, Part B. Vol. 1, Opinion 4, In: Technical Opinions of 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. P. 1-50, Porto Velho, Rondônia: Public Ministry of the State of Rondônia. 2 Vol. Available in:

[4] Tundisi, JG, Carvalho, NO & Alam, S. 2007. Technical Note Sediments, Models and Water Levels. April 10, 2007. Annex III, p. 1-11 In: FURNAS, CNO. Answers to Questions Presented by IBAMA in the Framework of the Environmental Licensing Process for the Madeira Complex, Technical Information Nos. 17, 19 and 20/2007 COHID/CGENE/DILIC/IBAMA. Rio de janeiro Brazil. Furnas Centrais Elétricas SA (FURNAS) & Construtora Noberto Odebrecht SA (CNO), Available at:

[5] FURNAS & CNO. 2007. Answers to Questions Submitted by IBAMA in the Scope of the Environmental Licensing Process of the Madeira Complex, Technical Information Nos. 17, 19 and 20/2007 COHID/CGENE/DILIC/IBAMA. Rio de Janeiro, RJ: Furnas Centrais Elétricas SA (FURNAS) & Construtora Noberto Odebrecht SA (CNO), Annex III. Available in:

[6] Molina Carpio, J. 2007. About the preliminary report by Sultan Alam. La Paz, Bolivia: FOBMADE. Available in:

[7] Alam, S. 2007. Rio Madeira Project: Hydraulic and Sediment Management Studies. Brasília, DF: Ministry of Mines and Energy. Available in:

[8] Op. cit. Note [7] (Alam, 2007): p. 20.

[9] Op. cit. Note [7] (Alam, 2007): p.8.

[10] PCE; CNO & FURNAS. 2007. Madeira River Hydroelectric Complex: Feasibility studies for AHE Jirau. Supplementary report PJ0633-V-H00-GR-RL-002-0 March/2007. Engineering Projects and Consulting Ltd. (PCE), Construtora Noberto Odebrecht, SA (CNO). Rio de Janeiro, RJ: Furnas Centrais Elétricas SA (FURNAS), p. 11.

[11] Op. cit. Note [5] (FURNAS & CNO, 2007): Annex IV.

[12] Op. cit. Note [7] (Alam, 2007): p. 39.

[13] Dunne, T. 2007. Response to analyzes of flow and sedimentation at the sites of proposed Rio Madeira hydroelectric projects, 8 July 2007, Report to International Rivers, Berkeley, California, USA Available at:

[14] 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).

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Madeira-Sediments River Dams 1: Series Summary

Madeira-Sediments 2 river dams: The first official scenario

Madeira-Sediments 3 river dams: The second official scenario

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).

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