Serra da Mesa Dam

The Serra da Mesa Dam, once known as Sao Felix, is an embankment dam on the Tocantins River near Minaçu in Goiás, Brazil. The dam serves an associated hydroelectric power plant with a 1275 MW installed capacity. The dam creates the largest reservoir 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 long and 154 m tall earth-fill embankment dam with a clay core and in total contains 12057558 m3 of material. The reservoir created by the dam has a capacity of 54400000000 m3 and surface area of 1784 km2. Of the reservoir's volume, 43250000000 m3 is active storage. The dam supports a spillway with five floodgates that are 15 m wide and 20.4 m high each. In total, the spillway has a 15000 m3/s discharge capacity.

Serra da Mesa Hydroelectric Power Station
The dam supports the Serra da Mesa Hydroelectric Power Station, an underground power station and hydraulic circuit. Before reaching the turbines, water enters the intake near the dam's left abutment and proceeds along three 24 m long intake tunnels before reaching three 126 m long and 10 m diameter penstocks. Water then reaches the Francis turbines which power three 425 MW generators. After exiting the turbines, the water is discharged from the power house via one 500 m long tailrace tunnel. The power house is 137 m long, 67 m high and 30 m wide. To mitigate water hammer when starting and stopping the turbines, it contains a 69 m long 20 m wide and 65 m tall surge chamber with a 91000 m3 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.