Porce III Dam

The Porce III Dam is an embankment dam on the Porce River 90 km northeast of Medellín in Antioquia Department, Colombia. The dam was constructed between 2004 and 2011 for the primary purpose of hydroelectric power generation.

Background
Between 1974 and 1976, hydrological studies were carried out on the Porce River and between 1982 and 1983, studies regarding the river's hydroelectric development were completed. The study recommended the five projects, Porce I, Porce II, Porce III, Porce IV and Ermitaño. In December 1984, the feasibility report for Porce III was submitted and complementary studies were carried out between 1986 and 1996. In 2002, the design and consultancy contracts were awarded along with the environmental license issued. In 2004, construction on the dam began and the river was diverted by 2007. By 2010, the dam began to impound the reservoir and was complete by 2010. Between 2011, all four generators were commissioned.

Design and operation
The Porce III Dam is a 151 m tall and 426 m long concrete-face rock-fill type embankment dam. Its base width is about 400 m and it has a fill volume of 4155000 m3. The dam's spillway is a chute-type and is located on its left side. It is controlled by four radial gates and has a maximum discharge of 10850 m3/s. The reservoir created by the dam has a 170000000 m3 capacity of which 127000000 m3 is active capacity. The reservoir has a surface area of 4.6 km2. The catchment area for the dam and reservoir is 3756 km2. A submerged intake on the reservoir's left bank conducts water to the power station initially via a 12 m long and 10.2 m diameter upper headrace tunnel. At the terminus of this short tunnel, the water drops 149 m vertical shaft to the lower headrace tunnel which has the same diameter of the upper but is 304 m long. At the end of the lower headrace, it converts into four penstocks to supply each of the underground power house's 211 MW Francis turbines with water. Once ejected from the power plant, it enters over 1000 m of tailrace tunneling and is returned to the Porce River.