Breaking down physical and social barriers to connect the Alviela River.
The Alviela River, with a length of 45 km, once flowed freely to the Tagus. Today, 33 barriers block the passage of fish and sediments, transforming the natural landscape and contributing to biodiversity loss and coastal erosion, loss of connectivity and other forms of habitat degradation, including pollution, have a negative effect on fish species. As a result of these pressures in the fish species present in the Alviela river, one endemic species, the Portuguese arched-mouth nase (Iberochondrostoma lusitanicum) is considered critically endangered, and two native species, the European eel (Anguilla anguilla) and the Southern Iberian chub (Squalius pyrenaicus) are identified as endangered.
This project contributes to improving longitudinal connectivity, reversing the decline of migratory fish, reducing coastal erosion, improving water quality, engaging people, and promoting climate action.
| Project status | Completed |
|---|---|
| Project type | Dam removal: demolition |
| Country | Portugal |
| River | Alviela |
| Removal date | November 2025 |
| Km to be opened | 4.3 km |
| Focal species | Portuguese arched-mouth nase, European eel, Southern Iberian chub |
| Organisation | GEOTA |
| Website | rioslivres.geota.pt |
GEOTA is implementing the Rollin’Rivers project, funded by DIMFE (Jan 2023 – Dec 2025), which includes, in the Alviela sub-basin, the mapping and characterisation of barriers to river connectivity and other preparatory work aimed at developing river rehabilitation projects. This includes communication, outreach, stakeholder mapping and engagement, and a public participation process.
A barrier in the Alviela River was already removed in 2023 as part of this project. After developing a methodology for characterising and prioritising obsolete dams, it was applied to the Alviela Basin. The analysis concluded that, to increase longitudinal connectivity and ecological benefits, the removal of five obsolete dams is recommended. The Sourinho dam, which will be removed with support from the Open Rivers Programme, is one of these five.
The objective of this project is to develop a river restoration project in the Alviela River through the removal of the obsolete Sourinho dam, thereby improving hydrological connectivity, engaging people, and promoting climate action.
The project’s team expects the removal of the Sourinho dam to represent a significant step toward the implementation of the National Plan for the Removal of Obsolete Dams and to help dismantle not only physical but also cultural, social, and political barriers.
The project, led by the GEOTA through the Rios Livres Programme, successfully removed the Sourinho dam in the Alviela River, previously defined as a priority for dam removal in a basin-scale assessment.
At the ecological level, this dam removal resulted in an improvement of ecological conditions, increasing the connectivity for water, sediments and migratory fish. The connectivity was restored for a total of 4.3 km upstream along the Alviela River, including tributaries. Key species benefiting from these efforts include the Portuguese arched-mouth nase (Iberochondrostoma lusitanicum), the European eel (Anguilla anguilla), and the Southern Iberian chub (Squalius pyrenaicus).
At the social level, the project was developed emphasising community engagement and stakeholder integration (including local governments, local environmental associations, regulatory entities, and academic entities), using effective communication strategies and a science-based approach to promote effective public participation.
Overall, the project contributed to improved river connectivity, to an increase in public awareness regarding the importance of dam removal, and to the sustainable management of Portuguese rivers.
Funded by
