CASE-STUDY
By reconnecting the Alviela, the Rolling’Rivers project is not only improving ecological health but also fostering collaboration, awareness, and action for rivers and communities.
Alviela River
The Alviela sub-basin, situated in the Tagus Basin approximately 100 km north of Lisbon, is home to unique geological features and a diverse array of fauna and flora.
Through the Rolling’Rivers project, GEOTA is developing an integrated approach to river restoration that combines science, society, and activism to promote healthy, connected river ecosystems.
GEOTA is focused on the removal of obsolete dams that fragment the river and threaten biodiversity. After mapping and assessing all barriers in the Alviela sub-basin, they established prioritisation criteria and created intervention scenarios.
Fish
Macroinvertebrates
The Connect team is conducting intensive fieldwork focused on benthic macroinvertebrate sampling during the pre-removal phase. Samples are collected and analysed from reference points along the Alviela River study site to obtain detailed baseline data on community structure, abundance, and functional diversity. This targeted methodology enables precise tracking of ecological responses and changes in macroinvertebrate communities after dam removal. The resulting findings will offer insights into river ecosystem recovery and inform both scientific understanding and sustainable management practices.
Sourinho weir
The Sourinho weir is a concrete structure measuring 2 m in height and 30 m in width. In the past, it was likely used for industrial purposes (such as olive oil mills and tanneries) and for agriculture and irrigation. Today, however, the dam is obsolete and no longer in use.
The Alviela River, where the dam is located, is home to threatened species such as the Iberian chub (Squalius pyrenaicus) and the European eel (Anguilla anguilla). Currently, there is no functional fish passage. Although the weir is partially destroyed, allowing limited flow continuity, it still poses a significant barrier to fish migration and river connectivity.