PHILIP M. FEARNSIDE
The second official scenario: no sedimentation
Questions about sedimentation prompted the Ministry of Mines and Energy to hire an international consultant to produce a report on the problem. [1]. When the report was released in April 2007, Dilma Rousseff (then Chief of Staff of Brazil and now President of the Republic) hailed the document as demonstrating that the sediment problem could be “discarded” [2]. Unfortunately, the report did not give such an endorsement, but suggested a complete overhaul of the Santo Antônio dam and recommended that a physical model of the dam and reservoir be constructed to test how sediment can accumulate. Furthermore, the report only concerns the Santo Antônio dam, not the Jirau dam, where the effects of sediments are even more controversial because of their potential impacts on Bolivia.
Sultan Alam [1] based his analysis on the Brune curve [3]instead of considering the model used in the EIA/RIMA: the 2001 version of the HEC-6 model (current version: [4]). The Brune curve provides a simple rule of thumb for assessing the mean potential for sedimentation in reservoirs. It is widely used for the calculation of trapping efficiency (the percentage of sediment retained in the reservoir) because of the simplicity of the curve: the only inputs required are the annual river flow, the volume of the reservoir and a rough classification of three levels of diameter of the sediment particles. Indeed, it is composed of a family of three graph curves on the retention efficiency as a function of the capacity-to-input ratio (eg, m3 of reservoir volume/m3 annual flow).
The upper curve represents coarse sedimentation, the lower curve represents fine sediments, and the middle curve, which is the most frequently used, represents a mixture of the two. The Brune curve is described by Dunne [5] as a “very approximate tool”, which he believes should clearly not serve as a basis for decisions on something as important as the dams on the Madeira River. The merits and uncertainties of different methods for predicting sediment retention by reservoirs are reviewed in Reid and Dunne. [6]. More complex models of sediment routing (such as RIVER-12 [7]) are necessary to account for non-linear effects such as those caused by irregularities in the channel path and vertical profile, as well as compartments and other features along the river banks. [5].
Sultan Alam [1] argues that the lower curve, corresponding to fine sediments (<0.25 mm in diameter), should be used for dams on the Madeira River. However, the Madeira River transports approximately 3.75 × 106 tons of sediment in the range of 1-3 mm in diameter, plus an additional value in the range of 0.25-1 mm [8]. Though not mentioned by Alam [1], if the standard Brune curve procedures were applied to these sediments, the middle curve or the upper curve would have to be applied to them, and in neither case would the amount of trapped sediments be zero in the Madeira dams. alam [1] uses a different justification for coarser sediments, namely that peak flows would release them. For the movement of the sand, Alam [9] used calculations based on Rouse’s equations. This procedure is criticized by Dunne [5]which writes:
“I didn’t find Alam’s Rouse equation analysis helpful in analyzing the likely fate of dams. Although based on a relatively well-established equation, Alam’s analysis does not take into account the amplitude and duration of the main controller over sediment transport, which is the flow regime.”
A technical note written to tenderers by Tundisi et al . [10] summarizes the results of the Brune curve as follows:
“The independent analysis performed by Dr. Sultan Alam corroborates the observation that the use of the lower envelope of the Brune curve applied to the case of fine sediments of the Madeira River predicts zero retention of sediments, that is, the absence of permanent siltation that causes future over-elevation of water levels due to sediment deposition”.
The technical note extends Alam’s conclusion to Abunan (i.e., including Jirau):
“The analysis carried out by consultant Dr. Sultan Alam made it possible to conclude that the stretch of the Madeira River between Abunã and Porto Velho has the capacity to transport practically all the sediment of the Madeira River, even with the construction of the Jirau and Santo Antônio projects. The fine sediments (clays, silts and part of the sands with a diameter of < 0.25 mm), even with reservoirs, will be transported in suspension or saltitation, continuously, due to the high transport capacity in all months of the year. Larger sediments will also be transported during the flood months (at least 4 months of the year) when they are mobilized, as is currently the case.” [11].
The new technical notes state that there would be no accumulation of sediment in the upper part of the Jirau Reservoir (and, consequently, the formation of a backwater affecting Bolivia):
“Due to the characteristics of the reservoirs, classified as ”reservoirs – gutters”, ‘deltas’ will not be formed by sedimentation upstream of the reservoirs. This condition occurs in accumulation reservoirs and not in typical ‘run-of-the-river’ reservoirs with high energy gradients. Thus, the correct prediction is that all sediments from the Madeira River will continue to be transported downstream, even after the construction of the Jirau and Santo Antônio dams” [11].
During the critical days in 2007, when pressure was building to approve the dams, Sultan Alam was asked to endorse the dams as free of sediment limitations. Correspondence, via e-mail, with Alam is reproduced as proof of its support, in the bidders’ response to IBAMA’s inquiries. [12]. Alam’s email says:
“TO WHOM IT MAY CONCERN. I, Sultan Alam, independent consultant, certify that I fully agree with the text in Portuguese by answering several questions asked by IBAMA. Sultan Alam, May 10, 2007”.
Although his email mentions that the document he was endorsing was written in Portuguese (which is not a language he speaks), it can be assumed that the content of the 239-page text was adequately explained to him, particularly the relevant technical notes.[13, 14]. The technical notes in question are largely dedicated to the Jirau dam (especially to issues involving Bolivia), rather than the Santo Antônio dam, which was the subject of consultant Alam’s report. [1]. The consultant’s report [15] indicates that the Alam visit (December 15-17, 2006) was confined to the first 17 km of the future Santo Antônio reservoir.
The endorsement made by Alam was a key factor in quashing the concerns raised by IBAMA. It should be noted that, despite Sultan Alam being repeatedly referred to in the Brazilian press as “the World Bank consultant”, he was not working in that capacity here (nor should his report be regarded as representing a Bank opinion). However, the World Bank lent the Ministry of Mines and Energy a US$250,000 “package” to hire consultants, one of whom was Sultan Alam. [16, 17].
See the Infoamazônia map of the Madeira River basin formed by the waters of the Beni, Madre de Dios, Mamoré and Guaporé rivers.
GRADES
[1] Alam, S. 2007. Rio Madeira Project: Hydraulic and Sediment Management Studies. Brasília, DF: Ministry of Mines and Energy. Available in:
[2] Peixoto, P. 2007. Dilma pressures Ibama over 2 plants: Minister says that the sediment problem of the Madeira River, in Rondônia, has been solved, but the threat to catfish continues. Newspaper , April 24, 2007, p. B-9.
[3] Brune, GM 1953. Trap efficiency of reservoirs. Transactions of the American Geophysical Union 34(3): 407-418.
[4] US Army Corps of Engineers. 2012. HEC-6: Scour and Deposition in Rivers and Reservoirs. HEC-6 V4.1. Available in:
[5] 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:
[6] Reid, LM & Dunne, T. 1996. Rapid Evaluation of Sediment Budgets . Reiskirchen, Germany: Catena Verlag.
[7] Chang, HH 2006. Generalized Computer Program. FLUVIAL-12: Mathematical Model for Erodible Channels. Users’ Manual . Rancho Santa Fe, California, USA: Chang Consultants. Available in:
[8] Op. cit. Note [1] (Alam, 2007): p. 8.
[9] Op. cit. Note [1] (Alam, 2007): p. 22.
[10] 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), p. 7. Available at:
[11] Op. cit. Note 10 (Tundisi et al ., 2007): p. 4.
[12] 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, Brazil : Furnas Centrais Elétricas SA (FURNAS) & Construtora Noberto Odebrecht SA (CNO), Annex IV. Available in:
[13] Carvalho, NO, Salgado, JCM, Cadman, JD & Madeira, EF 2007. Technical Note March 26, 2007. Subject: Technical Opinion No. 014/2007-COHID/CGENE/DILIC/IBAMA, of March 21, 2007. Annex II, p. 1-11. In: FURNAS & CNO. Answers to Questions Submitted by IBAMA in the Framework 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, Brazil : Furnas Centrais Elétricas SA (FURNAS) & Construtora Noberto Odebrecht SA (CNO). Available in:
[14] Op. cit. Note 10 (Tundisi et al ., 2007).
[15] Op. cit. Note [1] (Alam, 2007): p. 4.
[16] Salomon, M. 2007. Government does not clarify the impact of the dams: Technical notes sent by the Ministry of Mines and Energy to Ibama do not eliminate doubts about the dams. Newspaper , April 28, 2007, p. A-7.
[17] 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).
Read too:
Madeira-Sediments River Dams 1: Series Summary
Madeira-Sediments 2 river dams: The first official scenario
Madeira-Sediments 4 river dams: Expert opinion and official scenarios
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). Read more about his profile and others columnists here.
