Vaqueiros Weir, Portugal

A project that transformed community and political perspective towards barrier removal in Portugal

The River Alviela
The River Alviela basin is located in the central-east Portugal (Figure 1) and is characterized by high biodiversity and encompasses three important and protected/classified areas: the Serras de Aires e Candeeiros Comunitarian site of interest, the Natural Park of Serras de Aires e Candeeiros and the Natural Reserve and Special Protection Area for Avifauna of Paúl do Boquilobo, located about 4.9 km east of the Alviela. This sub-basin inhabits several endemic and rare or vulnerable species of flora, such as the Butomus umbellatus and the Hydrocharis morus-ranae. The latter species is present only in the River Alviela sub-basin and not in the entire basin.

Figure 1. Location of the River Alviela sub-basin in central-east Portugal

The River Alviela rises from the Serra da Mendiga and flows into the River Tagus (Figure 1), covering a length of approximately 51 km. The hydrographic basin of the River Alviela, with an area of about 333 km², covers several municipalities, including Alcanena and Santarém. Historically the River Alviela was of great importance for the River Tagus basin but on a national level as well. Local communities remember it as a river of clean, fresh, transparent waters and with plenty of fish from various species. More specifically, the river, once navigable by small rowing boats, was abundant with barbels, cyprinids, and eels, much appreciated by the riverside populations.

Due to various anthropogenic pressures, including degraded water quality caused by agricultural, livestock and industrial pollution (mainly tannery industries), and hydrogeomorphological alterations that affected the connectivity of the river system, fish populations have been declining. The fish species under most pressure in River Alviela are: the European eel (Anguilla anguilla), the Portuguese-Boga (Iberochondrostoma lusitanicum) and the Southern squalius (Squalius pyrenaicus) (Figure 2). Declines have been observed also in autochthonous riparian vegetation, such as ash, willow and alder trees.

Figure 2. Main fish species of River Alviela

The River Alviela basin is also considerably fragmented by artificial barriers. Up to date there have been identified 33 such structures, including 13 weirs, 14 road crossings and 2 levees (Figure 3).

Figure 3. Identified barriers within the River Alviela basin

The Vaqueiros Weir 
One of the barriers that used to fragment River Alviela was the Vaqueiros Weir (Figure 4). This 1.1-m-high and 14-m-long structure (Figure 5) was built to support infrastructure of the leather processing industry that used to operate in the area. The date of the weir construction is unknown, but the associated factory ceased to operate in the 1980s. In the past, the weir had multiple “functions”, as it was used by the local community for leisure, passage between riverbanks, artisanal fishing and washing of clothes.

Figure 4. The location of the Vaqueiros Weir at River Alviela

Figure 5. The Vaqueiros Weir at River Alviela © GEOTA

Dam removal
In Portugal the national agency that supervises the application of the law and regulates the framework of rehabilitation actions and removal of barriers is the Portuguese Environment Agency (APA). The riverbanks in the country are mostly privately owned and infrastructures built on the riverbed are property of those who build them (provided that their construction is licensed). The Portuguese legislation that regulates the water resources management is generally based on the Water Framework Directive, the Water Law and the Public Water Domain. At the moment, there are no specific regulations for the removal of barriers in Portugal, in which case the general law applies.

The project that led to the removal of the Vaqueiros Weir began in June 2022 with preparatory meetings between the Rios Livres GEOTA Team and the municipalities involved (Video 1). After extensive talks, the weir owners’ consent to its removal. In September 2022, the development of the project began, and in the following three months (October-December) the process to acquire the necessary licenses started.

Video 1. The Vaqueiros Weir removal project at River Alviela © GEOTA

The demolition works of the Vaqueiros Weir (Figure 6) started in April 2023 and were completed during the same month (Picture 7; Video 2). This project aimed to reestablish connectivity of River Alviela, but also to promote a National Program for Dam Removal. The project was initially conducted within the framework of the RIR (Reconnecting Iberian Rivers) program, which was funded by the MAVA Foundation and was then developed and finalized within the ROLLIN’ RIVERS project – People, Knowledge and Action to Enhance River Restoration in Portugal, funded by DIMFE (The Donors’ Initiative for Mediterranean Freshwater Ecosystems). The cost of the total project was 50000 €.

Video 2. Removal works of the Vaqueiros Weir at River Alviela © GEOTA

Figure 6. Removal works of the Vaqueiros Weir at River Alviela in April 2023 © GEOTA

Figure 7. The removal site after the demolition of the Vaqueiros Weir at River Alviela © GEOTA

Challenges
The major challenge the project managers faced from the start was the difficulty in communicating the scope of the project to the local community. Since barrier removal is a rarely implemented practice in Portugal, a cultural resistance was observed towards the idea of removing this barrier, as barriers are still concerned countrywide as beneficial structures for the communities. That also made the active engagement of the local community and the relevant stakeholders a difficult endeavor. The fact that the percentage of elderly in the local community was significant, as well as that three municipalities had to be involved, made things more challenging. Multiple field visits and sessions (Video 1) were needed to start persuading the involved parties for the detrimental effects of river fragmentation, for the benefits the barrier removal would provide and the overall necessity of the project.

Ecological and community benefits
The removal of the Vaqueiros Weir restored the connectivity and ecological continuity at River Alviela for a significant proportion of the river. Fish migration, natural sedimentation and water flow were reestablished. An additional ecological benefit provided by the project was the consolidation of the river banks adjacent to the former barrier by using natural engineering techniques. The riparian vegetation was also reformed by replacing invasive species with native ones (Figure 8).

Figure 8. Planting of native species at the demolition site of the Vaqueiros Weir at River Alviela © GEOTA

Beside the ecological benefits of the project, a significant achievement was the transformation of the perception of the local community and the political authorities towards barrier removal. GEOTA views the removal of physical barriers and the restoration of river connectivity as an opportunity to also remove social barriers and reconnect people and rivers. This project promoted curiosity, dialogue and participation. By its completion, the project was greatly accepted by locals and stakeholders alike.

In a country where most municipalities see river barriers as an asset, this project was a pioneer by including two municipalities and sharing a vision of a restored river. The impact of this project was evident by the presence of the central government at the celebrating event of the barrier removal, where they publicly announced a National Program for the removal of obsolete dams.

The removal of the Vaqueiros Weir project was crowned winner of the Dam Removal Award 2023 during a ceremony held Tuesday, April 16, at the Free Flow Conference, in Groningen, The Netherlands (Figure 9). After being pre-selected as one of the top three projects by an independent jury of international experts, an open voting round took place in which the public voted on their favorite finalist project. The jury’s and the public’s opinions were considered on a 50-50 ratio and the final count of votes elected the Vaqueiros Weir project as the Dam Removal Europe Award 2023 winner. The award is hosted by Dam Removal Europe, the World Fish Migration Foundation, the European Investment Bank, The Nature Conservancy, and supported by the Dutch Postcode Lottery and Forest Peace Foundation.

Figure 9. The removal of the Vaqueiros Weir project crowned winner of the Dam Removal Award 2023 on April 16 2024 at the Free Flow Conference in Groningen, The Netherlands

Before & After photo pair

The removal site at: (left) before and (right) after the demolition of the Vaqueiros Weir © GEOTA

With many thanks to GEOTA for providing the information and the visuals presented herein.

Prepared by Foivos A. Mouchlianitis