The Serra da Mesa Dam, once known as Sao Felix, is an embankment dam

Embankment dam

An embankment dam is a massive artificial water barrier. It is typically created by the emplacement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay and/or rock. It has a semi-permanent waterproof natural covering for its surface, and a dense, waterproof...

 on the Tocantins River

Tocantins River

The Tocantins is a river in Brazil, the central fluvial artery of the country. In the Tupi language, its name means "toucan's beak" . It runs from south to north for about 2,640 km. It is not really a branch of the Amazon River, although usually so considered, since its waters flow into the...

 near Minaçu

Minaçu

Minaçu is a small city and municipality in the north of the state of Goiás, Brazil. There is a large asbestos mine in the municipality.-Location and climate:...

 in Goiás

Goiás

Goiás is a state of Brazil, located in the central part of the country. The name Goiás comes from the name of an indigenous community...

, Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

. The dam serves an associated hydroelectric power plant with a 1,275 MW installed capacity. The dam creates the largest reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

 by volume in Brazil.

Background

Eletrobrás Furnas began studies of the upper Tocantins River in 1981 and proposed constructing two large dams, one was at Serra da Mesa which had good geomechanical conditions. After years of studies, construction on the dam and power station began in 1986. On October 24, 1996, the dam began to inundate and create its reservoir and it was full in 1998; around the same time, the power station's generators became operational.

Dam and reservoir

The Serra da Mesa Dam is a 1500 m (4,921.3 ft) long and 154 m (505.2 ft) tall earth-fill embankment dam with a clay core and in total contains 12057558 cubic metre of material. The reservoir created by the dam has a capacity of 54400000000 cubic metre and surface area of 1784 square kilometre. Of the reservoir's volume, 43250000000 cubic metre is active (live or "useful") storage. The dam supports a spillway

Spillway

A spillway is a structure used to provide the controlled release of flows from a dam or levee into a downstream area, typically being the river that was dammed. In the UK they may be known as overflow channels. Spillways release floods so that the water does not overtop and damage or even destroy...

 with five floodgates that are 15 m (49.2 ft) wide and 20.4 m (66.9 ft) high each. In total, the spillway has a 15000 m3/s discharge capacity.

Power station

The dam supports an underground power station

Underground power station

An underground power station is a type of hydroelectric power station constructed by excavating the major components from rock, rather than the more common surface-based construction methods....

 and hydraulic circuit

Hydraulic circuit

A hydraulic circuit is a system comprising an interconnected set of discrete components that transport liquid. The purpose of this system may be to control where fluid flows or to control fluid pressure...

. Before reaching the turbines, water enters the intake near the dam's left abutment and proceeds along three 24 m (78.7 ft) long intake tunnels before reaching three 126 m (413.4 ft) long and 10 m (32.8 ft) diameter penstock

Penstock

A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....

s. Water then reaches the Francis turbine

Francis turbine

The Francis turbine is a type of water turbine that was developed by James B. Francis in Lowell, Massachusetts. It is an inward-flow reaction turbine that combines radial and axial flow concepts....

s which power three 425 MW generators. After exiting the turbines, the water is discharged from the power house via one 500 m (1,640.4 ft) long tailrace tunnel. The power house is 137 m (449.5 ft) long, 67 m (219.8 ft) high and 30 m (98.4 ft) wide. To mitigate water hammer

Water hammer

Water hammer is a pressure surge or wave resulting when a fluid in motion is forced to stop or change direction suddenly . Water hammer commonly occurs when a valve is closed suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe...

 when starting and stopping the turbines, it contains a 69 m (226.4 ft) long 20 m (65.6 ft) wide and 65 m (213.3 ft) tall surge chamber with a 91000 cubic metre capacity.

Environmental impact

The Serra da Mesa Dam was sharply criticized by environmentalists before and during construction. Organizations, such as the International Rivers Network criticized the dam and its reservoir for destroying a vast area of flora and fauna along with destroying the habitat of endangered species. In addition, the dam was criticized for flooding archeological sites and $15 million worth of timber that was not removed prior to flooding.