Barragem de Maranhão, Hydroelectric dam in Alcórrego e Maranhão, Portugal

The Barragem de Maranhão is an earthfill dam on the Ribeira de Seda, completed in 1957. Its crest is about 204 m long and 10 m wide, carrying a pale concrete roadway with a low wall and dark metal railing; the left slope is grey gravel, the right face steeper and rocky. It rises 49 m above the natural ground and holds a 205.4 hm³ reservoir.

The dam was built in 1957 as part of Portugal's modernization plan to boost electricity generation during the mid-twentieth century. It became an important project for expanding hydropower use in the Portalegre region.

The reservoir is popular for sport fishing, a use that draws anglers to the water. The dam belongs to the Associação de Regantes e Beneficiários do Vale do Sorraia and, with the Montargil and Magos dams, feeds the Sorraia Canal, which carries water to farmland in the valley.

Visitors can enjoy views across the water and surrounding landscape from the dam, with access usually available from local roads. Keep in mind that safety regulations apply around the facility and some areas may not be freely accessible.

The dam is an earthfill structure: its volume of 592,000 m³ is gravel and crushed stone, not concrete, as the grey slope visible from the crest shows. Its crest road runs 204 m at an altitude of 133 m, and the Francis turbine supplied by VA Tech Escher Wyss sits in a powerhouse at the foot of the dam.