Volume 6 hydro power 6 04 – large hydropower plants of brazil

Volume 6 hydro power 6 04 – large hydropower plants of brazil Volume 6 hydro power 6 04 – large hydropower plants of brazil Volume 6 hydro power 6 04 – large hydropower plants of brazil Volume 6 hydro power 6 04 – large hydropower plants of brazil Volume 6 hydro power 6 04 – large hydropower plants of brazil

6.04.1.1 Historical Evolution of the Electric Sector in Brazil

6.04.1.2 Main Hydroelectric Projects

6.04.2 The 14 000 MW Itaipu Hydroelectric Project

6.04.2.1 General Description of the Project

6.04.3 The 8125 MW Tucurui Hydroelectric Project

6.04.4.1 The Santo Antonio Project

6.04.5 The Iguaçu River Projects

6.04.5.1 The Foz do Areia Project

6.04.5.3 The Salto Santiago Project

6.04.5.4 The Salto Osorio Project

6.04.5.5 The Salto Caxias Project

References

6.04.1 Introduction and Background

Brazil is located in South America where it occupies 47.7% of the territory of this continent Brazil has the fourth largest territorial area in the world Its 8.5 million km2 spans from latitude 4° north to 33° south, and from longitude 75° to 40° west Its population

is of about 190 million people Economically, it is the eighth largest economy of the world with a gross national product equivalent

to about US$1.6 trillion [1] Politically, it is a federation of 27 states with a diversified legislation on the use of natural resources giving, in general, to the central government primary (but not exclusive) prerogatives on the licensing to build and operate infrastructure undertakings, including hydraulic and hydroelectric projects

The right to explore the use of water resources is granted to public and/or private agents through concessions In the case of hydroelectric projects, concessions for selected projects are offered by the federal agency for electric power (Agencia Nacional

De Energia Elétrica, ANEEL) for interested parties under a competitive tendering process The concessionaires are supposed to sell the electric power to the retailing companies with a preestablished tariff, which is the basis for the competitive tendering process The National System Operator, which manages the National Interconnect Transmission System, daily defines the generation level of each plant, so as to optimize the overall availability of hydrological resources and the use of regulating reservoirs The compensation for the concessionaire is not dependent on the power produced by his plant but he receives a fixed amount coresponding to a virtual

‘firm energy’ associated with his plant which was established by ANEEL prior to the concession tendering process

Brazil is a country extremely rich in water resources Although certain areas of the country can be classified as having a semiarid environment, for its seasonal intermittent rainfall pattern, the Brazilian territory is well endowed with tropical and subtropical humid climates, with a predominance of perennial drainages projected by tablelands and lower plateaus This of course favors the rather extensive use of water resources for the development and well-being of its population, with hydroelectric power generation, urban water supply, and river flow regulation being the main objectives of projects carried on

Figure 1 depicts schematically the main river basins on the Brazilian territory

As a result, the construction of hydroelectric projects, dams, and reservoirs was the object of an important effort by the Brazilian people, through both government and private initiatives The most important dams in Brazil were built in relation to hydroelectric projects Presently (August 2009), 74.3% of the electric power installed capacity in the country originates from hydroelectric

are responsible elsewhere by the bulk of the electric power generation needs

developments This, of course, reflects not only the abundance of hydroelectric potential but also the scarcity of fossil fuels, which

Figure 1 Main Brazilian river basins 1, Amazon Basin – 3.8 million km2

; 2, Paraná-Uruguay Basin – 1.4 million km2

; 3, Tocantins-Araguaia Basin – 0.97 million km2

; 4, San Francisco Basin – 0.63 million km2

; 5, Eastern Atlantic Basin – 0.57 million km2

; 6, Northeastern Atlantic Basin – 1.0 million km2

; 7, Southeastern Atlantic Basin – 0.23 million km2

Actually the hydroelectric prevalence and the existence of different hydrologic regimes in different areas of the country and the existence of an interconnected, countrywide, HV transmission system make the Brazilian generation system different from that of any other country in the world In July 2009, the total installed capacity of hydroelectric generating plants was 78 126.3 MW, not considering 7000 MW, which is the Paraguayan share of the Itaipu project, which however is mostly sold to the Brazilian system [2] The total production of electric power generated from hydroelectric projects offered to the Brazilian market in 2008 was 363.8 TWh, corresponding to 73.1% of the total from all sources These figures are expected to grow at an annual rate of 3–4%, in spite of the fact that efforts toward building more fossil-fueled plants, mainly using natural gas, are underway The main reason for the accelerated growth of thermal plants is the increasing opposition of environmentalists to the realization of hydraulic regulating reservoirs

6.04.1.1 Historical Evolution of the Electric Sector in Brazil

The first hydroelectric plant in Brazil was built in the industrial state of Minas Gerais, in southwest Brazil in 1889 It was a 252 kW power plant, which provided electric power for public lighting for the town of Juiz de Fora [3] In the early 1900s, electricity utility companies controlled by private foreign capital started developing the hydroelectric potential to supply electric power to São Paulo and Rio de Janeiro, the main urban and industrial centers of the country In 1901, the Canadian company São Paulo Light and Power Company inaugurated the first major plant in the São Paulo area, in the Tietê River, a dam that today is practically located within the boundaries of the city (Edgard de Souza dam) In 1907, the Rio de Janeiro Light and Power Company completed the construction of the Fontes hydroelectric project, with dam and power plant generating 24 000 kW, then one of the largest hydro­electric projects in the world

From the beginning of the century to the mid-1930s, the construction of dams and plants for electric power generation remained with private companies, practically without government interference In 1934, however, the federal government issued new legislation considering the country water resources as public property and started to issue concessions for the use of these resources

by private agents, for any purpose including power generation, urban supply, and irrigation

With the end of World War II, in Brazil as elsewhere, the idea of a direct participation of governments in the economic activities related to infrastructure works, creating conditions for an accelerated industrial development, started to flourish within government planning offices and leading industry entrepreneurs The first major centrally formulated economical development plan for the country was created by the federal government administration that took office in 1946 This prepared the setting for the following administration, which started in 1950 with a deep nationalistic view of government and public participation in promoting development, to act and implement a number of public-owned companies that were given the responsibility of building infrastructure works in such diverse areas as electric power, oil, roads and highways, irrigation, and land development The first major state-owned company established to develop the electric power potential of Brazilian hydroelectric resources, Chesf (Companhia Hidrelétrica do São Francisco), was created in 1948 with the specific responsibility of building a major dam and power plant at the Paulo Afonso Falls, in the São Francisco River, in the southern limits of the Brazilian northeast The Paulo Afonso plant began operation in 1954 and presently four powerhouses have been built in the site, with a total installed capacity of

3400 MW

of power in the major industrial southcentral and southern states of the country By the end of the 1950s, a new and important central government-owned company – Furnas – was created to build a new and large plant in the Grande River, between Minas Gerais and São Paulo This company eventually grew to build a large number of dams and generating plants and was a key player in developing and securing dam and hydroelectric technologies required to implement larger and more powerful plants in rivers of the southcentral region

In São Paulo, the most industrialized state of the Brazilian Union, by the mid-1950s, dam construction and electric power generation was primarily done by São Paulo Light and Power Company, which, as mentioned above, was established in the area since the beginning of the century To promote further development in the more distant areas of the interior of the state, the state government set up companies with responsibilities of developing the hydro potential of the main state river basins, following to a certain extent the successful example of the American TVA – Tennessee Valley Authority – that during previous decades was the major example of the government interference in a private-dominated sector of the economy The development of the three major rivers of the state, the Tietê, the Paranapanema, and the Paraná, was assigned to new companies, and these rivers, in less than

20 years, were completely transformed with dams, reservoirs, and hydro plants, some of which were benchmarks in the develop­ment of dam engineering in Brazil

Until the end of the 1950s, the expansion of generation and transmission facilities in Brazil, as in many parts of the world, was carried out by separate utilities operating on a local basis As the better hydro sites close to the local loads were developed, and annual growth began to approach 400 MW or more, regional planning of the expansion of generating became important, and some

of the state utilities began to realize that a broader survey of hydro resources in their area became mandatory [4, 5] In 1961 a survey

of the hydro potential of the south central area of the country, followed by a similar survey of the southern region, was carried out This resulted in one of the major systematic surveys of hydro resources ever carried out anywhere in the world with specific technological and methodological procedures developed for the study The study covered an area of about 1.3 million km2 and identified and appraised hundreds of potential hydro sites Most of them were implemented during the following 40 years and became the backbone of the Brazilian electric system

The growth of public utilities in Brazil had, by the early 1970s, in practical terms completely eliminated the private competitors, which were either absorbed or extinguished along the process Each state created its own public company responsible for supplying electric power, either by purchasing from other state-owned companies or building their own hydraulic projects On the federal level, the central government assigned Eletrobras as their holding company, with four subsidiaries – Chesf, Furnas, Eletronorte, and Eletrosul – covering the whole of the Brazilian territory and responding for the construction and operation of large dams and power projects and for the interconnected transmission system

Major projects built between the early 1950s and 1980s, under the sponsorship of state-owned companies, are among the most important ever built in the country Among these were the 14 000 MW Itaipu project, then the largest hydroelectric project in the world; the 2500 MW Foz do Areia project, with a 160 m high dam, at the time the highest concrete-face rockfill dam in the world; the

3200 MW Ilha Solteira project; the pioneering 1216 MW Furnas project; and the 2680 MW São Simão project are significant examples of the diversified engineering and construction achievements of the Brazilian hydro engineering of the period

By the beginning of the 1980s, the Brazilian economy entered into a period of stagnation resulting from various factors, including increases in the international price of oil, of which the country was extremely dependent, and instabilities in the world financial markets, in general This period caused the halting of about a dozen dam projects that suffered a lack of funds for proceeding with construction already started while some others, in spite of concessions to some utilities, could not even have their works started

In spite of this unfavorable situation some major dam projects, such as the 8000 MW Tucurui project, the first large dam project

in the Amazonian area, had their first phase (4000 MW) completed Other important projects, such as the 5000 MW Xingó project and 1200 MW Segredo project, proceeded and were completed during the decade However, the poor financial and economical situation of some of the state-owned utilities prevented the increased raising of capital resources required to keep up with the very large needs of the country in hydropower and dam construction The consequence was the return to the private market to finance the expansion of the sector

Privatization of the electric power sector and dam construction in Brazil, during the 1990s, actually meant the complete reformulation of rules of operation and access to concession of hydropower sites One major federal electric generating utility and some large state-owned power companies were sold to private parties, some of them belonging to international corporations This has brought in a reasonable inflow of badly needed capital and, as a consequence, the resumption of dam and power plant projects previously halted

Presently, the rules for owning and operating electric power plants in Brazil allow the participation of private and public parties, either independently or in association The federal government produces an inventory of possible sites, evaluates their technical feasibility and defines the technical and environmental requirements, and organizes the priorities for development Concessions for building and operating plants during 30 years are granted to interested parties under competitive dispute on public auctions in which the winner is the party that offers the lowest price for selling the energy (kWh) to the integrated system that is responsible for transmitting and distributing, through local companies, the electric power

6.04.1.2 Main Hydroelectric Projects

Presently (2009), there are 517 hydroelectric projects in operation in Brazil with an aggregated installed capacity of 78 218.4 MW There are also 91 hydroelectric projects under construction that will have a combined capacity of 11 537.8 MW [6] These figures do not include projects that are being studied and for which concessions have not been granted It does not include, for example, the

11 000 MW Belo Monte project that will be offered for concession early in 2010

In continuation, some representative hydroelectric Brazilian projects are presented as samples of the type of projects built in the country

6.04.2 The 14 000 MW Itaipu Hydroelectric Project

The Itaipu hydroelectric project is presently the second largest hydroelectric generating installation in the world It is a joint undertaking between Brazil and Paraguay, located in the Paraná River, in a reach in which this river constitutes the international border between the two countries (Figure 2) Construction of the project started in May 1975 and the first 700 MW unit entered into commercial operation in May 1984 The installation of 18 units was carried out from 1984 to 1991 and the last 2 units were only added in 2006 completing the full capacity of the project

The realization of this major binational hydroelectric project, which until recently was the largest in the world, was made possible by extensive diplomatic negotiations between Brazil and Paraguay These negotiations culminated with the signing

by the two countries, in 1966, of a document setting up the intention of jointly studying and evaluating the hydroelectric potential of the international reach of the Paraná River Furthermore, the agreement established that the hydroelectric power produced in this stretch would be equally divided between the two countries and that each country would have the preferential right to acquire the power owned by the other country that it would not use for its own domestic consumption Based on the Brazil–Paraguay agreement, a Joint Technical Commission was created in 1967 and feasibility studies were carried out that concluded by the recommendation of a single project to be implemented to develop the full power potential of the international reach of the river As a result a treaty was signed in 1973, and a binational entity – Itaipu Binacional – was formed by both countries to conduct the construction of the project and, subsequently, operate it [7]

The project was essentially financed by international loans guaranteed by the Brazilian government It has been in continued and very successful operation since the first unit entered on line in 1984 About 95% of the energy produced is fed into the Brazilian electric system and the 5% balance represents the domestic Paraguayan consumption

6.04.2.1 General Description of the Project

The information and description that follows is essentially based on the book The Paraná River basin covers an area of about

3 million km2, of which 899 000 km2 are in the Brazilian territory with the remaining in Paraguay, Argentina, and Uruguay The drainage area at the Itaipu site is 820 000 km2 The upper stretches of the Paraná basin are located in the central mainland of Brazil, with elevations between 600 and 700 m When the river reaches the international border, at Guaira, the elevation is about 215 m and from this point onto the Itaipu site it drop 140 m Practically, all this drop was concentrated at the Sete Quedas Falls, now flooded by the Itaipu reservoir

Figure 2 Project location

The average natural annual flow at the Itaipu site, computed without consideration of the existing upstream reservoirs, is

9700 m3 s−1 Most of the upstream reaches of the Paraná River and of its main tributaries are already developed for hydroelectric generating projects and this has created a significant regulating capacity that naturally influenced the power studies Another important factor in these studies is the fact that Iguaçu River discharges into the Paraná immediately downstream of the Itaipu site, creating large variations on the elevation of the water level depending on the flow regime of both rivers, and therefore affecting the head available for power generation

The final basic installation was defined with 18 units with a nominal capacity of 700 MW each, corresponding to 12 600 MW Two additional units were considered to allow more flexibility in the plant operation and maintenance These units were installed in

2006, and presently the plant has a total capacity of 14 000 MW

The Itaipu site has rather good geological characteristics for the construction of a hydro project It is located in an area underlain

by the basalt flows that cover the upper Paraná basin The basalt flows at the site are essentially horizontal with thickness varying from 20 to 60 m with breccia layers between the flows, with thickness from 1 to 30 m The massive basalt rock has excellent mechanical properties and is suitable both as foundation for the structures and as construction material The breccia, however, is relatively weak and heterogeneous The formulation of the project involved very extensive studies and investigations, including more than 30 000 m of core drilling, almost 400 m of shafts, 1600 m of tunnels, and 660 m of trenches

The extensive hydrologic studies performed were based on data collected from 59 stream gauging stations and 65 meteorological stations located in Brazil, Paraguay, and Argentina and on data from the 136 planned and existing reservoirs that affect flow at the site Flood studies were computed during feasibility studies based on the Probable Maximum Flood (PMF) concept and were eventually recomputed and confirmed with data from the unprecedented high floods that occurred in 1982–83 over the Paraná basin The maximum peak inflow at the site was established as 72 020 m3 s−1 and the hydrograph was routed through the reservoir to define the spillway design flood For the design of the river diversion structures, the 100-year flood corresponding to 35 000 m3 s−1 was selected The layout locates the powerhouse at the middle of the river that is flanked on the right bank by a curved (in plan) concrete buttress dam up the spillway site, continuing after the spillway by an earthfill dam closing the valley (Figure 3) On the left bank the powerhouse is crossed by the diversion channel, where three units are located, continues with a concrete buttress dam followed by a rockfill dam and an earthfill section closing the valley

River diversion was done through a channel excavated on the left bank A concrete gravity structure aligned with the main dam, and ultimately becoming part of it, housed the 12 sluiceways, 6.7 m wide by 22 m high, controlled by diversion gates Concrete arch cofferdams were built for the construction of the diversion structure These cofferdams were later blasted and removed to allow the flow of the river through the sluiceways The sequence and key dates of the river diversion scheme are depicted in Figure 4 The whole sequence and features of the diversion operation were tested in hydraulic models carried out by the Federal University

of Paraná hydraulic laboratory, in Curitiba, Brazil Final closure of the diversion gates was carried out on 13 October 1982 and was completed successfully in 8 min The flow of the Paraná River was 12 000 m3 s−1 and the reservoir was filled in 15 days As provided

by the design, the diversion gates were recovered and used for the power intake Storage in reservoirs on the Iguaçu River provided the riparian flow for downstream reaches of the Paraná River, during the filling of the Itaipu reservoir

Figure 3 Project general layout 1, Right bank earthfill dam; 2, Spillway; 3, Right bank hollow gravity dam; 4, Main dam and power intakes; 5, Diversion channel dam and intakes; 6, Left bank concrete dam; 7, Left bank rockfill dam; 8, Left bank earthfill dam; 9, Powerhouse at river channel

4728 m, adding up to a total length of 7750 m The maximum height of the dam is 196 m, measured from the foundation at the central part of the river

The central stretch concrete dam is formed by 18 hollow gravity blocks The 16 blocks located immediately upstream of the powerhouse support the power intake The blocks are monolithic cells, each consisting of an upstream head supported by two

near the crest and the foundation, there are no major openings crossing the buttress dam portion

The closing portion of the dam at the right side of the valley and a part of the left wing dam (numbered 7 in Figure 3) are earth-core rockfill dams The earthfill stretch of the dam on the left bank was selected because of the availability of adequate soil material in the area The maximum height of this stretch is 30 m and its length is 630 m

6.04.2.3 The Spillway

The Itaipu spillway is a gated surface chute spillway with capacity of passing 62 200 m3 s−1 with the reservoir at the full supply level at

El 223 It is located on the right bank of the Paraná River and is divided into three independent chutes to allow operational flexibility and capability to safely handle emergencies, and for that, each chute can discharge about twice the average natural flow of the river The spillway has an ogee-shaped control structure with 14 segment-type (tainter) gates, 20 m wide by 21.34 m high supported by

5 m wide piers Its total width is 380 m and maximum length is 483 m Each chute has a different length and longitudinal profile, fitted to the location and foundation surface The chutes end in a flip-bucket configuration to provide energy dissipation without damage to permanent works and without significant surcharge of the powerhouse tailwater The specific discharge of the spillway is

183 m3 s−1m−1 and the exit velocity is 40 m s−1 The design of the spillway including the geometry of the buckets was extensively tested with hydraulic models in Curitiba, Brazil

The hydraulic performance of the spillway was satisfactory and essentially free of major problems Some lateral erosion in the rock was observed in the downstream plunge pool This was, to a certain degree, forecasted in the model studies, although in one case it did affect the left side of the chute immediately downstream of the bucket [8] This has been associated with the unusually intense operation of the spillway in the first years after its commissioning In fact, due to the schedule of the installation of generating equipment, during the first 3 years all three chutes of the spillway operated almost continuously after reservoir impounding Thereafter, for the next 3 years one or two of the chutes operated continuously This is rather unusual in hydroelectric projects, but it represented a unique opportunity to check spillway design and the result confirmed the excellence of it It is estimated that during the five initial years of operation about 500 TWh of energy passed over the Itaipu spillway

6.04.2.4 The Power Plant

The Itaipu power plant is formed by 20 generating units, each with a capacity of 700 MW The powerhouse is located immediately downstream of the dam, in the central part of the river The power intake is located on top of the hollow gravity dam and allows short penstocks to reach the generating units

A special characteristic of the Itaipu power plant is that half of the units generate power in 60 Hz and half in 50 Hz, respectively, according to frequencies of the Brazilian and Paraguayan electrical systems The power generated at 18 kV is transformed at the GIS step-up substation, located immediately upstream of the powerhouse, to 500 kV, and from there connected to the respective systems in each country As mentioned earlier, each country has the right to purchase and use the excess power not used for domestic supply For that reason the Brazilian side is also connected to the 50 Hz generating system and in Brazil is converted into direct current, transmitted to the São Paulo area, reconverted to AC 60 Hz and fed into the country integrated transmission system

Figure 5 depicts a typical transversal section of the powerhouse with indication of its main installation features

All power intakes are identical in configuration, design, and equipment The Itaipu plant was planned to operate as a run-of-river plant, with a normal maximum drawdown of 1 m with possibility, in an emergency situation at the spillway, to deplete the reservoir level to the elevation of the spillway sill Figure 6 shows a typical cross section of the power intake

The penstocks are made of welded steel, with an internal diameter of 10.5 m, and feed directly to the turbines as indicated in

Figure 5 They are anchored to the dam and embedded in second-stage concrete placed in a large blockout in the face of the dam The powerhouse is an independent 968 m long structure located at the toe of the main dam It contains the 20 bays of the units, along with two equipment erection and maintenance areas, and miscellaneous areas for technicians and operators The central control room is located downstream from the powerhouse in an independent building Figure 7 shows a sketchy representation of the powerhouse arrangement and an external view of the powerhouse and administration building

Each unit bay is 34 m wide and is 94 m high, from El 50 to El 144 It houses a turbine-generator unit, three main unit single-phase step-up transformers, switchgear, and mechanical and electrical auxiliary equipment

The right-bank erection area has an unloading, unpacking, and preassembly area at El 144 and is served by two 2.5 kN cranes accessing the main assembly area at El 108 This main assembly area is 141.3 m long and 29 m wide The central erection area has also an unpacking and preassembly area at El 144 with another two 2.5 kN cranes that can also access the main assembly area The central control room is located downstream at El 135, between units 9A and 10 with a viewing area above El 139 The turbines are of Francis type, and were specified to develop 715 MW at the rated head of 112.9 m The head for overall best efficiency was 118.4 m Performance of the turbines so far has been excellent They have been commissioned without any problem

Figure 5 Typical section of the Itaipu powerhouse 1, Upstream road; 2, elevators; 3, transmission line take-offs; 4, downstream road; 5, powerhouse upstream ventilation rooms; 6, GIS; 7, electrical equipment gallery; 8, electrical cable gallery; 9, ventilation equipment gallery; 10, battery room; 11, local unit control room; 12, generator hall; 13, main transformers gallery; 14, penstock; 15, electrical auxiliary and excitation equipment gallery; 16, generator;

17, turbine; 18, spiral case; 19, draft tube; 20, drainage gallery; 21, mechanical equipment gallery; 22, pumps, strainers, and piping gallery; 23, anti-flooding gallery; 24, draft tube stop-log storage; 25, main powerhouse crane (10 MN); 26, gantry crane 1.4 MN; 27, main transformers crane 2.5 MN;

28, GIS equipment crane

Figure 6 Typical cross section of the power intake 1, Trashracks; 2, stop logs; 3, intake gate; 4, gate maintenance chamber; 5, air vent; 6, 1100 kN gantry crane; 7, trashrack cleaning machine; 8, penstock; 9, bypass valve; 10, intake-gate servomotor; 11, transmission line

Figure 7 Powerhouse layout and external view 1, Equipment unloading building; 2, right-bank erection area; 3, transformer unloading area; 4, auxiliary service transformers; 5, vertical circulation access; 6, transmission line take-offs; 7, central control room; 8, central erection area; 9, draft-tube stop-log hatches; 10, penstocks; 11, upstream road; 12, downstream road; 13, tailrace; 14, dam and power intakes; 15, operation and administration building; 16, river-bed powerhouse; 17, diversion-channel powerhouse

and have operated in a satisfactory way for many years The only repair work carried out was related to minor cavitation damage in the runners, probably associated with low load operation

Because of the need to produce electric current at different frequencies, half of the generators generate at 50 Hz and the other half

at 60 Hz, all of them driven by identical turbines of 715 MW rated capacity The 60 Hz generators have a rated power factor of 0.95, which corresponds to a rated output of 737 MVA considering a generator efficiency of 0.98 The power factor of the 50 Hz generators

is 0.85, corresponding to a rated output of 823.6 MVA

6.04.3 The 8125 MW Tucurui Hydroelectric Project

The Tucurui project is the second largest hydroelectric project in the Brazilian territory and the largest installation that is 100% Brazilian [9–11] It is located in the Tocantins River in the state of Pará, in northern Brazil It was built, is owned, and is operated by Eletronorte – a federal government public utility for electric power responsible for the bulk supply of electric power in the northern region of Brazil The project was designed by the Brazilian consulting firms Engevix and Themag and built by contractor Camargo Correa The construction supervision was done directly by Eletronorte

The Tocantins River and its main tributary, the Araguaia River, is one of the major river systems in the Brazilian territory (see Figure 1) Its total drainage area is 967 059 km2, of which 758 000 km2 are upstream of the Tucurui site The Tocantins River headwaters are located in the central part of Brazil, at an elevation of about 800 m above sea level (m asl), where the country’s capital, Brasilia, is located Its course runs essentially in a south–north direction for a length of about 2500 km discharging in the estuary of the Amazon River near the city of Belém, capital of the state of Pará

The Tucurui project is the furthest downstream hydroelectric project contemplated in the cascade of projects of the Tocantins River, which include five other projects presently in operation (Serra da Mesa, 1275 MW; Canabrava, 465 MW; São Salvador,

243 MW; Peixe Angical, 452 MW; and Lageado, 903 MW), one under construction (Estreito, 1087 MW), and four being studied (Ipueiras, 480 MW; Tuparitins, 620 MW; Serra Quebrada, 1328 MW; and Marabá, 2160 MW)

Figure 8 General layout of the Tucurui project

The Tocantins River at Tucurui has a wide valley with low topography The project layout displayed the structures in sequence, with the spillway followed by the power plant on the riverbed area near the left bank and the remainder of the valley closed to the right and to the left by rockfill dams This arrangement has allowed the isolation of the area for the second-stage power plant and provided initial structures for the future incorporation of navigation locks Figure 8 shows the general layout of the project The full installed generating capacity of the Tucurui project is 8125 MW, which was achieved in two stages The works corresponding to the initial stage included the rockfill dams in both margins, the spillway, and half of the power plant with an installation of 12 units, each with rated output of 330 MW and two 20 MW auxiliary ones, totaling 4000 MW This was done between 1976 and 1984 To the left of the first-stage power plant, an area was isolated by cofferdams to allow the later second-stage power plant, which was completed in 2007, increasing the project capacity to 8125 MW

For the construction of the project, river diversion and control during the works posed major challenges, not only because of the magnitude of the flows to be managed but also because the river bottom was found to be extremely irregular with rock channels and sand deposits that complicated considerably the construction of impervious cofferdams The initial construction sequence considered a two-phase diversion, which consisted of earth-rockfill cofferdams isolating areas in both margins, the construction of the spillway structure with sluiceways underneath to handle the river during the second phase and final closing of sluiceways to start reservoir impounding The initial studies, including the project basic design, considered that cofferdams were to be designed for the 50-year recurrence flood of 51 000 m3 s−1 However, in

1980, with cofferdams built in the left margin and construction in progress, a major flood of 68 400 m3 s−1 occurred, exceeding by 33% the diversion design flood This size of flood had never occurred in the historical record of 100 years

[12] Exceptional circumstances as the widening of the constricted river channel due to previous flood erosions on the opposite margin and a conservative freeboard in the cofferdams luckily prevented the construction site to be flooded The event forced a modification of the river diversion scheme, which was changed from a two- to a three-phase sequence The flood event changed the hydrologic series and the 50-year design flood was recalculated to be equal to 58 600 m3 s−1 Except for this exceptional event, which fortunately did not affect the construction area and did not change the construc­tion schedule, the realization of the project was accomplished successfully

The Tucurui spillway is one of the largest in the world, with a design capacity of 110 000 m3 s−1 It is a gated spillway structure incorporated into the mass concrete of the dam It is equipped with 23 radial gates, each 20.0 m wide by 20.75 m high The discharge

of the spilled flow into the river is done through a cylindrical shaped bucket that issues a jet hitting the water surface between 80 and

130 m away from the toe of the structure and over an excavated plunge pool The maximum specific flow over the bucket, 207.0 m3 s−1m−1, is also a very high figure in comparison with other projects elsewhere

Underneath the spillway, there were 40 diversion sluiceways, 6.5 m wide by 13.0 m high, which were used to close the river and start reservoir impounding Figure 9 shows a view of the spillway structure with the diversion sluiceways Closure operation used

20 steel recoverable gates to close the upstream entrance of each sluiceway and precast concrete stop logs to close the downstream end These were lowered from the downstream bridge after the flow in each passage was interrupted by the upstream recoverable steel gate

Figure 9 View of the Tucurui spillway during construction

The Tucurui power plant has two powerhouses Figure 10 shows the cross section of the first power plant

The first power plant built with the initial project works includes 12 main units and 2 auxiliary ones, as indicated before The second one that was built while the first one was operating contains 11 units with an individual capacity of 375 MW Except for the difference in unit capacity, the arrangements of the two powerhouses are similar

The power intake is a gravity-type structure divided into blocks corresponding to the generating units The penstocks are imbedded in the structure as shown in Figure 10 The powerhouses, located at the toe of the power intakes, are essentially similar

to each other and are of the sheltered type with auxiliary service galleries placed downstream whose structure supports the power transformers

The Tucurui project incorporates locks that allow the navigability of the river linking the agriculture productive areas of the central plateau of Brazil to the port of Belém

Figure 10 Typical section of the Tucurui first power plant

The Tucurui power plant is linked to the interconnected Brazilian transmission system through 500 kV lines and has been, since the commissioning of the first powerhouse, a key factor to ensure the adequate supply of electric power to the country

6.04.4 The 6450 MW Madeira Hydroelectric Complex

The Madeira hydroelectric complex is formed by two projects located in sequence on the Madeira River, in the state of Rondonia in northwest Brazil These two projects are presently (2009) under construction and are expected to be on line by 2012 The upstream project is the Jirau project, with an installed capacity of 3450 MW and the other is the Santo Antonio project with an installed capacity of 3150 MW

The Madeira River is the main tributary of the southern bank of the Amazon River Its course is 1450 km long Its headwaters are located on the Andes Mountains in Bolivia, with the name of Beni River Its course follows initially the south–north direction changing to the SE–NE direction after receiving the waters of the Guaporé River and entering the Brazilian territory first as a border river and then traveling inland

The hydroelectric potential of the Madeira River was evaluated by a comprehensive study carried out under the sponsorship of Eletrobras, the Brazilian federal agency for electric power with a view to developing power projects and extending inland navigation along the river The intention was to define these projects in the context of the Initiative for the Integration of the Regional Infrastructure of South America (IIRSA), a combined effort by several South American countries [13] As a result of this study, two projects were defined to develop the head between El 90, where the river starts to run inside Brazil, and El 50 downstream of the Santo Antonio rapids This stretch of the river is 250 km long and after its lower end it will still run for about 1000 km before reaching the main course of the Amazon River

Figure 11 shows a map with the location of the Jirau and Santo Antonio projects, which constitute the Madeira hydroelectric complex The Santo Antonio project is located 10 km upstream of the city of Porto Velho, capital of the state of Rondonia, and Jirau

110 km upstream Both undertakings are very low head projects and were designed to have a minimum increase in the natural flood level of the river They incorporate navigation locks and separate passageways for migrant fishes that abound in the river The concession for construction and operation of the projects was the object of a competitive tendering process in two independent auctions As a result the Jirau project was awarded to a group of private- and state-owned companies led

by GDF-Suez Energy and including Camargo Correa – a Brazilian contractor – and Chesf and Eletrosul – state-owned utilities Similarly, the Santo Antonio project was awarded to a consortium led by Odebrecht – a Brazilian contractor – and Furnas – a state-owned utility

JIRAU PROJECT

SANTO ANTONIO PROJECT

STATE OF AMAZONAS

Figure 11 Location of the Madeira hydroelectric projects

Intertechne Its construction started in September 2008 and the program calls for the first generating unit be on line in May 2012 and the 44th unit, in June 2015, encompassing 81 months to complete the whole project

The Madeira River at Santo Antonio has an average flow of 18 000 m3 s−1 The spillway design flood is 84 000 m3 s−1, which makes it the second largest in Brazil, after the Tucurui spillway

The project utilizes the head of 13.9 m created by the dam It contains 44 generating units of the bulb type each driven by horizontal-shaft turbines The project layout was defined taking into consideration, besides local topographical and hydrological consideration, the construction sequence and the maximum possible anticipation of the production of power The layout placed the various structures in a linear sequence but considered three separate powerhouses, one near the right bank, one near the left bank, and one in the middle of the river (Figure 12) Since the project head is low, and its dams are of course of modest height, it will be possible to generate power (and income) before the third powerhouse is completed while being protected by cofferdams The two powerhouses close to the left bank will have 24 units (units 9–32) and three assembling areas for the equipment installation Following these powerhouses is the main spillway with 15 passages controlled by radial gates, each 20.0 m wide by 24.18 m high, supported by 5.0 m wide pillars In sequence the third powerhouse located at the middle of the river contains 12 units (units 33–44) and 2 assembling areas This third powerhouse is connected to the main spillway on its right side To the left side, concrete gravity dams make the connection to the complementary spillway This last spillway will have three passages also controlled by radial gates of the same size as the main spillway After this spillway, in the direction of the right bank, the fourth powerhouse will contain eight units (units 1–8) and one assembling area On both margins the concrete structures are comple­mented by earth dams to close the section

The total installed capacity of the project is 3150 MW, formed by 24 units with nominal capacity of 73.28 MW and 20 units with 69.59 MW The powerhouses are formed by typical modules, each including four units sharing the same step-up transformer and formed by two structurally independent blocks Each four-unit module is 85 m wide by 72.9 m long by 58.2 m high Figure 13

depicts a typical section of the unit block

The river diversion and control during construction took into consideration the marked seasonality of the Madeira River, which has wet and flood period from July to November concentrating, on the average, 45–60% of the larger annual floods The river diversion sequences were programmed with isolating areas on both margins, and, after the construction of the main spillway, divert the river through it The construction sequence and the natural river conditions allowed the selection of different design floods for the protection of different parts of the works, from 100-year recurrence flood for channel and major excavation works to 300-year floods for relevant concrete structures The 100-year flood is of the order of 40 000 m3 s−1 (June–November) and the 300-year flood, for the same period, is approximately 45 000 m3 s−1

Figure 12 General layout of the Santo Antonio project

Figure 13 Typical section of the Santo Antonio powerhouse

Figure 14 View of the construction site of the Santo Antonio project in September 2009

The main construction quantities involved in the construction of the Santo Antonio project (Figure 14) are the following: Soil excavation 38.4 million m3

Rock excavation 21.2 million m3

Concrete (conventional) 2.3 million m3

RCC (rolled compacted concrete) 0.8 million m3

6.04.4.2 The Jirau Project

The Jirau project, located upstream of the Santo Antonio project, is being built, under direct owner coordination, by Brazilian contractor CamargoCorrea Main electromechanical equipment is being supplied by an association of major suppliers, including Alstom, Voith, Andritz, and DEC Engineering design of the works is being carried out by Brazilian consulting firm Themag Leme Engenharia is acting

as Owner’s Engineer Its construction started in April 2009 and the first unit is programmed to be on line in March 2012

Figure 15 General layout of the Jirau project

The project site is located in a wider stretch of the river where an island in the middle of the river will be used to facilitate the river diversion during construction Figure 15 shows the project layout

The project layout displays the various structures aligned, forming a ‘V’ with its vertex on the river island The project will utilize the maximum head of 19.9 m created by the dam and install 46 generating units with unit capacity of 75 MW driven by bulb turbines with horizontal axis The total installed capacity will be of 3450 MW

The project will have two powerhouses: one (PH 1) in the main course of the river, on the right-hand side of the island, with 28 units; and the other (PH 2) on the channel excavated on the left bank, with 18 units There will be only one spillway to discharge the maximum design flood of 82 600 m3 s−1, with 18 passages controlled by radial gates 20.0 m wide by 21.82 m high Between the spillway and PH 2, there will be an earth-rock dam 575 m long and with a maximum height of 53 m

River diversion will be done isolating the area between the right bank and the middle-river island by two roughly parallel cofferdams In this area the spillway and powerhouse PH 1 will be built while the river is flowing on the channel close to the opposite margin The second-phase diversion will be through the spillway, while the left bank is being protected by cofferdams

Figure 16 shows a view of the construction stage in November 2009

Figure 16 View of the construction site of the Jirau project in November 2009

6.04.5 The Iguaçu River Projects

The information for this section was based on material compiled in Reference [14] The Iguaçu River is one of the main tributaries of the middle course of the Paraná River It drains a basin of about 69 000 km2 and runs essentially in an east–west direction through a length of about 1000 km, from its headwaters, near the city of Curitiba, in the state of Paraná, to its mouth in the Paraná River, immediately downstream of the Itaipu project Along its course it drops more than 800 m, frequently through concentrated steps, among which the internationally famous, Iguaçu Falls For about 90% of its length, it runs inland in the Brazilian territory, in the state of Paraná, but for the last 120 km downstream it constitutes the border between Argentina and Brazil

The natural conditions of the basin favor the hydroelectric development The topography of the area with concentrated drops of the rivers, a geologic configuration formed by basalt flows, and a subtropical climate with no definite dry seasons allowing an average of more than 1300 mm of annual rainfall throughout the basin provide a substantial power potential that was implemented in six major projects cascading along the Brazilian reach of the river There are no projects in the international reach that is relatively flat upstream of the Iguaçu Falls At the site of these falls, so far no project has been seriously considered as well, and surely there will never be one The hydroelectric projects built on the Iguaçu River are the following:

Project name

Ultimate capacity (MW)

Present installed capacity

Foz do Areia Segredo Salto Santiago Salto Osorio Salto Caxias

All the Iguaçu River projects are connected to the Brazilian National Interconnect System mainly through 500 kV links

6.04.5.1 The Foz do Areia Project

The Foz do Areia project is the most upstream of the Iguaçu River projects It was built and is owned by COPEL the electric power utility of the state of Paraná It was designed to generate power at the site and to provide a regulating reservoir to benefit downstream projects Presently, its full regulating capacity is no longer used because the integrated system provides electrically this regulation and the avoidance of extreme depletion of the reservoir allows a larger generation of energy

The project was built between 1975 and 1980 It was designed by the Brazilian firm Milder-Kaiser Engenharia and built with two sequential construction contracts, one for diversion by Andrade Gutierrez S.A and rest of the project by CBPO – Companhia Brasileira de Projetos e Obras – of the Odebrecht Group

The project is located in the upper part of the middle course of the Iguaçu River at about 240 km from the city of Curitiba The local topography of the site does not present a concentrated step, as in other sites of the river The river, at the site, is relatively narrow and the abutments rise in step-type features, reflecting the superposition of basaltic flows The local sequence of rocks has a marked predominance of dense basalts with basaltic breccia making up the balance The soil and weathered rock mantle is unusually thick in the area This would have favored a soil-rockfill dam, but the excessive humidity of the site would have made

it expensive and would have affected the project schedule

Figure 17 shows a view of the completed project and Figure 18 depicts the general project layout The Foz do Areia project includes a concrete-face rockfill dam, a spillway and a power plant formed by a power intake, and six power tunnels feeding the external powerhouse containing six bays for 418.5 MW units, of which only four have been installed, and a GIS step-up substation River diversion for constructing the dam was done through two unlined tunnels, 12 m in diameter, excavated in the right abutment

A significant feature of the Foz do Areia project is its dam When it was completed in 1980, it was a world record for concrete-face rockfill dams, with its height of 160 m, and remained as such until the mid-1990s, when Aguamilpa, in Mexico, reached the height

of 190 m The dam included many engineering advancement details in the concrete-face design and construction that made it a reference milestone for this type of structure A view of the dam and appurtenant facilities immediately before reservoir impounding

is shown in Figure 19

The spillway of the Foz do Areia project is a gated chute spillway, located on the left abutment, designed for a discharge of

11 000 m3 s−1 corresponding to the 1/10 000 year maximum project flood The chute is 70.6 m wide and 400 m long, ends in a flip bucket to dissipate energy in the plunge pool excavated in the channel downstream The chute was provided with three aeration devices to prevent cavitation, which showed excellent results both in model and prototype tests and along the life of the structure As

a result of revised hydrological studies carried out after very large floods observed during the 1980s, the reservoir has been systematically operated below the normal operating level to provide additional volume to allow the safety discharge of the spillway

Figure 17 The Foz do Areia project

Figure 18 General layout of the Foz do Areia project

The power plant is depicted in Figure 20 The power intake is 72 m high, deeply excavated in the rock and sustained by a rock ledge left between the intake and the deep powerhouse excavations The power tunnels were excavated below this rock ledge reaching the external powerhouse downstream An extensive system of drainage was provided to assure the stability of the rock ledge

The powerhouse is an external structure, of the semi-outdoor type with four installed Francis-driven units, each with 418.5 MW capacity adding up to 1674 MW The powerhouse contains also two additional bays for future installation, which so far have not been equipped The GIS substation, as shown in Figure 20, is installed immediately upstream of the powerhouse

The performance of the project during almost 30 years of continuous operations has been excellent without any major problem