Aldeadávila Dam

Aldeadávila Dam is a concrete arch-gravity dam on the Douro River (also known as the Duero River) on the border between Spain and Portugal. The Douro River forms the international boundary between Portugal and Spain. The nearest Spanish town is Aldeadávila de la Ribera in the Province of Salamanca, about 11.3 kilometres (7.0 mi) to the east. The nearest Portuguese town is Fornos in Bragança District, about 8 kilometres (5.0 mi) to the southwest. The Portuguese side of the river around the dam site lies within the International Douro Natural Park.

About the dam

In 1864, Portugal and Spain signed the "Treaty of Limits" (ratified in 1866), which established the present international boundaries of the two nations. A treaty on transboundary rivers clarifying issues regarding the use of such rivers was signed and affirmed in 1912. A treaty regulating the development of hydroelectric facilities on the Douro River was signed in 1927. The Aldeadávila Dam was built by Spain pursuant to these treaties, and was the final dam to be built by Spain on the section of river alloted to that country.

The dam is 140 metres (460 ft) high and its cost was estimated in 1962 at US$60,000,000 (about $443.5 million in 2010 inflated-adjusted dollars). It was one of a series of very high dams built in Europe in the two decades after World War II which incorporated a downstream face inclined toward the upstream flow. This simplified the dam's design and construction (although it required more concrete to build), and more readily incorporated the spillways into the dam face. Indeed, the dam's face is nearly vertical. Design work on the dam began in 1956, and construction completed in 1963. The structure was built by the Iberdrola Ingeniería y Construcción construction firm. Pedro Martínez Artola was the design engineer. The dam was built on high-quality granite rock. During construction, grouting was used to fill cracks in the rock which ran parallel to the dam's foundation, and on the Portuguese bank where two fractures in the rock occurred. The underground power station and tunnels were excavated using a mining procedure known as large-chamber stoping, and the dam's use of this technique is considered a textbook example. The turbine and generator hall and the transformer hall were both cut from solid granite as well. The turbine and generator room is 140 metres (460 ft) long, 18 metres (59 ft) wide, and 40 metres (130 ft) deep. The total volume of excavated material for all halls, rooms, and abutments was 600,175 cubic metres (785,000 cu yd).

The structure has eight overflow gates which channel water into four spillways. The spillways incorporate side piers on the upstream face to more correctly channel water over the dam so that each spillway discharges the same amount of water. The spillways release their water slightly above the actual bed of the river, creating a waterfall effect when they are fully open. A spillway tunnel carved from granite in the right bank of the river augments the spillways and provides for additional overflow. The total spillway capacity is half that of Grand Coulee Dam. The Export-Import Bank of the United States provided $8.9 million (about $67.2 million in 2010 inflation-adjusted dollars) in credits in 1958 to Iberduero to enable it to purchase six 120 Megawatt (MW) turbines and other electrical equipment for the power generating station, all of which was supplied by American firms.

The dam won Spain an international reputation as a builder of very large dams. The dam's eye-catching, "ski jump" style spillways are its most noted feature, and have been called "outstanding" by leading dam engineers.

The canyon through which the Douro River flows is exceptionally deep and narrow, leaving behind a reservoir that has a relatively small surface area for its immense size. In some ways, this limits use of the reservoir for recreational activities. However, the Aldeadávila Dam reservoir is a popular one for boating.

Power plant

The Aldeadávila Dam has a 422 MW pumped-storage capability. The dam's power plant contains 2 x 211 MW pumped-storage generators than can generate power in the normal way by allowing water to flow through its turbines. However, during periods when the demand for electricity is low (such as evenings, weekends, or during seasonal fluctuations), the dam can use its excess power generating capacity to pump water back into the reservoir—enhancing reservoir capacity and storing water for periods when the demand for electricity is high. At the time it was constructed, the Aldeadávila Dam had the largest pumping station in Europe.

The Aldeadávila Dam has two diversion tunnels, each 1,400 metres (4,600 ft) in length. Each tunnel has a 53-metre (174 ft) high surge tank. The dam also contains more than 12 kilometres (7.5 mi) of tunnels which divert water to the electrical generation turbines. There are six penstock tunnels, each about 5 metres (16 ft) in diameter. The design of the penstocks and auxiliary spillways using these tunnels has proved to be an issue, however. Cavitation problems have damaged these tunnels in the past. Until the Alcantara Dam was built in 1969, the Aldeadávila Dam was the largest hydroelectric power plant in Europe. As of 2010, it remains the largest in Spain. The dam's hydroelectric power station originally housed six 170,000 horsepower Francis turbines which generated 718 MW, about half that of Hoover Dam. In 1987, the Aldeadávila II power station extension was completed, boosting generating capacity by 400 MW.

In popular culture

A 30-minute documentary about the dam, La presa de Aldeadávila, was produced by Iberduero (the power company that built the dam) in 1963. Several scenes in the 1965 David Lean film Doctor Zhivago were filmed at the Aldeadávila Dam. The dam's famous spillways were opened for the filming, and are shown in the motion picture open at full force. Another scene depicts workers walking into one of the dam's enormous tunnels. The final scenes of Antonio Mercero's 1972 film, La cabina (The Telephone Box) were also filmed inside the dam.