Castelo do Bode, 1951: the dam that lit Lisbon and now fills its taps

On Sunday 21 January 1951, people came in their thousands to a gorge on the River Zêzere, between Tomar and Abrantes. Across the valley stood a curved wall of concrete 115 metres high. Behind it, a lake that had begun filling the previous April already covered fields, mills and the old footpaths that had linked the villages of the two banks.3 sources3 sources

The two men who ran the country came to open it: Marshal Óscar Carmona, head of state since 1926 and elected President of the Republic in 1928, and António de Oliveira Salazar, President of the Council of Ministers. That month the first generating set in the power station at the foot of the dam had started to turn. Carmona was 81, and he died in Lisbon three months later, on 18 April 1951.3 sources3 sources

The local paper called it a festive day for all the Portuguese, a great national aspiration justified by the burden of importing coal. The dam was one of the first two large projects of a plan to light the country with its own rivers. It also drowned a valley, and seventy-five years on, its reservoir is where most of Lisbon's drinking water comes from.3 sources3 sources

Portugal came late to electricity. The first official statistics counted 314 power stations in 1927 and 395 at the end of 1928, only five of them with more than 7,000 horsepower. In 1927 hydropower made only about a quarter of the country's electricity. Most of the rest came from steam plants burning coal shipped from Britain, while Portugal's own mines and rivers lay largely unused.2 sources2 sources

Electricity was also scarce. In 1928 Portugal produced a third as much per head as Spain and about a ninth as much as Italy. Consumption was concentrated around the two big cities: in 1937 the districts of Porto and Lisbon used 60 per cent of the country's electricity, though in 1940 they held only 26 per cent of its people. In 1940 Portugal produced 460 GWh, of which only 40 per cent came from water.1 source1 source

Lisbon's light came largely from the Central Tejo, a coal-fired power station on the riverbank at Belém owned by the Companhias Reunidas de Gás e Electricidade (CRGE). It supplied the whole Lisbon region and ran continuously from 1909 to 1954. After the Second World War broke out, coal prices rose fivefold.2 sources2 sources

The engineer José Nascimento Ferreira Dias Júnior (1900–1966), a professor of electrical engineering at the Instituto Superior Técnico, spent the 1930s saying so in print. As head of the state's electrical services from 1931 and of the Junta de Electrificação Nacional from 1936, he wrote reports on what he called the four evils of Portuguese electricity: scattered production, narrow distribution, poor consumption and dependence on foreign energy.1 source1 source

Ferreira Dias got his chance in August 1940, when he joined the government as under-secretary of state for Commerce and Industry. With the backing of the economy minister, Rafael Duque, he carried his own project into law as Lei n.º 2002, on the electrification of the country, published in the Diário do Governo on 26 December 1944.1 source1 source

The law set out a national grid and a clear rule: electricity would be produced “mainly from hydraulic sources”, with thermal stations kept for reserve and support. Generation was to be concentrated in large plants, the transmission network extended, and consumption encouraged with tariffs that fell as use rose. The state would take a share in the companies given the big river concessions.3 sources3 sources

The government first cancelled two old concessions whose holders had missed the deadlines for starting work: the Cávado and Rabagão rivers in the north, and the Zêzere, held by a Lisbon transport and electricity company. In 1945, according to the historian José Martinho Gaspar, a British commission of seven technical experts came to study the schemes, and Castelo do Bode interested them most.2 sources2 sources

Two companies with mixed state and private capital were then created by deed: the Hidro-Eléctrica do Cávado, known as HICA, on 24 October 1945, and the Hidro-Eléctrica do Zêzere six days later. A third, the Companhia Nacional de Electricidade (CNE), founded on 14 April 1947 with Ferreira Dias as its chairman, was to build the high-voltage lines carrying their power to Lisbon and Porto. Marshall Plan aid paid for almost a third of its first stage.2 sources2 sources

Work began in March 1946 on the last stretch of the Zêzere, upstream of its confluence with the Nabão, on the border between the municipalities of Tomar and Abrantes. For five years the valley was a building site. Engineers chose a concrete arch-gravity dam, a curved wall that resists the water partly by its own weight and partly by pushing it sideways into the rock of the gorge, here gneiss and mica schist.4 sources4 sources

Some of the machinery had to come by road. The March–April 1950 issue of the magazine of the Automóvel Club de Portugal told how a lorry carrying a 64,500 kg rotor took 30 days to crawl from Lisbon to the dam. Centenarian trees were cut down, roads reinforced and bridges improvised; the truck knocked down walls and posts and broke down more than once. People organised outings to watch it pass.1 source1 source

The design changed along the way: the power station was planned for five turbines and received three. Newspapers of the 1950s put the total cost at 600,000 contos, the old unit of a thousand escudos. How many people built the dam, and how many were hurt doing it, is not recorded in the sources used here.2 sources2 sources

The scale was new for Portugal. In 1943 all 54 of the country's commercial hydroelectric stations, leaving aside factories' own plants, together had about 89,000 kW of capacity. Today Castelo do Bode alone is rated at 139 to 159 MW, between one and a half and nearly twice as much, though in January 1951 only the first of its three sets was turning.4 sources4 sources

When the dam was finished in 1950 the water rose fast, surprising people who had watched the works for years and still doubted there would be a lake. To make room for it, about 3,500 hectares of land, 1,000 urban buildings in several villages and 250 rural works such as mills and presses were expropriated. Some 1,400 landowners on the two banks were compensated.2 sources2 sources

In the municipality of Abrantes alone more than 30 water mills and presses went under, on the Zêzere and on tributaries such as the Brunheta, Souto and Ferraria streams. Families from Foz da Ribeira, Conqueiro, Pombeira, Videiral and Casal da Barca lost their houses. Others kept their homes but lost the fertile riverside fields, called nateiros, that the winter floods of streams such as the Codes had enriched.2 sources2 sources

The lake also cut old crossings. A week before the inauguration, on 14 January 1951, a resident of Souto complained in the Jornal de Abrantes that the rising water had severed paths, left villages almost isolated and that no real alternative routes had been built. A few ferries ran, but loading animals on them was hard and had already caused accidents.1 source1 source

Many people left the region with the money from expropriations that were, Gaspar writes, sometimes unclear. Some went to the Alentejo or the Tagus lezírias, the flat farmland of the Ribatejo, and some to South America. Those who stayed turned scrubland into fields and had to look for the water their riverside land had never lacked. Gaspar, who was born in Água das Casas beside the reservoir, found that some old people still preferred not to talk about it six decades later.1 source1 source

The first aim of Castelo do Bode was to supply Lisbon. The CNE's first line from the Zêzere to the capital had entered service in October 1949, and the Zêzere substation and the first transformer at Sacavém, on the city's northern edge, were working in January 1951. A line from the Zêzere to Porto followed in October 1951. From 1954 the Central Tejo stopped running continuously and stayed in limited service until the 1970s.3 sources3 sources

Castelo do Bode was the lowest step of a cascade. Upstream, the Cabril dam, also built by the Hidro-Eléctrica do Zêzere, opened in 1954, and the Bouçã dam in 1955. In the north, HICA's Venda Nova scheme in the Cávado basin opened in the same year as Castelo do Bode. A 2015 talk to Portugal's water-resources association called the 1950s the golden decade of hydroelectricity.4 sources4 sources

The result showed in the national figures. Hydropower, about 40 per cent of production in 1940, made about 95 per cent of Portugal's electricity in 1960. Its share then fell, to about half by 1980, and since 1990 it has swung with the rainfall from about a tenth (2005) to more than two-fifths (1996).3 sources3 sources

In 1969 the Zêzere, Cávado and Douro companies were merged with others into the Companhia Portuguesa de Electricidade. Today EDP runs the power station. Between 2020 and 2025 it produced an average of 305.6 GWh a year, according to the Portuguese Environment Agency (APA), equal to the consumption of about 230,000 people. In 2025 its output was about 1 per cent of the electricity Portugal used.4 sources4 sources

It still matters in a crisis. Hydro stations need little power to start and can do so in minutes, so Castelo do Bode is one of the plants kept ready to restart a dead grid. After the Iberian blackout of 28 April 2025 it helped re-energise the network, restoring power first around Abrantes.2 sources2 sources

For more than three decades the dam's main job was electricity. Lisbon drank from the Alviela aqueduct, opened in 1880, and from the Tagus at Valada, piped to the city from 1932. In the 1980s the reservoir's main purpose changed. In 1987 EPAL, Lisbon's water company, opened the Castelo do Bode system: an intake on the reservoir, a treatment plant at Asseiceira, near Tomar, and about 90 km of mains 1.8 metres wide to reservoirs at Vila Franca de Xira.4 sources4 sources

Estimates of how many people depend on it vary with what is counted. The regional planning body CCDR-LVT says more than 2 million in Greater Lisbon and neighbouring towns, about a fifth of the population; LNEC says about 2.5 million. In 2021 EPAL's innovation director told the Lusa news agency, in a report carried by Observador, that the Asseiceira plant supplies 3.5 million people; the report put that at Lisbon and more than 80 municipalities, about a third of the country.3 sources3 sources

The APA calls Castelo do Bode the largest source of public water supply and the second-largest reservoir in Portugal by storage. Only Alqueva, filled from 2002, holds more, about 4,150 million m³. Releases from the dam also push back the salt water that the spring tides carry up the Tagus in summer, which helps farmers irrigating downstream.4 sources4 sources

The lake that ended a way of life on the Zêzere is now a place people drive to for fun. River beaches line its shores at Aldeia do Mato and Fontes in Abrantes, Lago Azul and Dornes in Ferreira do Zêzere, Alverangel and Montes in Tomar, Trízio in Sertã and three more in Vila de Rei. There are wakeboarding stations at Dornes, Castanheira, Trízio and Aldeia do Mato.1 source1 source

The road along the top of the dam is one of the busiest crossings of the Zêzere, linking Abrantes and Tomar. Even so, the reservoir cut many of the old links between the two banks. The reservoir is classified as a protected public reservoir because its water supplies the population, a status set out in a Council of Ministers resolution of 2003.2 sources2 sources