Restoring 50 km of connectivity in the Côa River, Portugal

Introduction

The Greater Côa Valley is a culturally rich and biodiverse area close to the border between Portugal and Spain, in the district of Guarda in Portugal. Its broad range of habitats and species make it one of the most exciting wild areas of Portugal. The rural exodus and consequent abandonment of marginal land present an unprecedented, large-scale opportunity for rewilding and the comeback of wildlife, with more than 210 species of vertebrates already present, including several keystone species.

The Côa River flows 140 km from Serra das Mesas in the Malcata Mountains running into the Douro River and connecting Malcata Nature Reserve to the Douro International Park. Along its course, there are a great diversity of habitats and conditions, from the rich riparian forest and large flood plains in the south to spectacular gorges home from cliff nesting raptors and vultures, in the north.  Its basin, mostly granitic, covers an area of 2520 km2 and comprises 25 sub-basins. This project is focusing on the Côa River and the Massueime Stream tributary.

In the upper Côa, there are more than 80 sites of rock art and around 1200 engraved outcrops, including the most important collection of Palaeolithic open-air figurations, which led to the creation of the Côa Valley Archaeological Park in 1996 with the mission of managing, preserving, researching and showing to the public the rock art. The Great Route of the Côa Valley runs along the entire river allowing visitors to discover the spectacular natural, archaeological and cultural heritage of the region.

Project context and opportunity

In the early 90s, dam construction in the Upper Côa started but was suspended after the discovery of several ancient rock-art sites. Civil society claimed the significance of conserving the sites and saved the most important collection of Palaeolithic open-air art from being flooded. The great artistic and scientific value of the engravings earned recognition by UNESCO as a World Heritage Site in 1998. One year later, the upper Côa and Massueime rivers were included in the Natura 2000 Network as a Special Protection Area due to the importance of the river canyon for cliff-nesting birds, such as the Egyptian vulture, black stork and the golden eagle.

However, the obsolete walls of the dam, today known as Ensecadeiras do Côa, remain. They obstruct the connection of the Côa River and the Massueime Stream to the Douro River. The National Water Council identifies the Ensecadeiras do Côa dams as priority obsolete barriers to be removed and an aim in the Catchment Plan of Douro River. Removing these structures is both a symbol of civil society power and the recognition of the natural and cultural heritage of the Côa Valley.

Project aims

This project focuses on completing those activities that are necessary to prepare for the removal of two barriers, the two walls of Ensecadeiras do Côa, from a legal, technical, ecological and social perspective. These activities include an environmental assessment, a civil engineering feasibility study, studies to determine sediment-related effects of barrier removal as well as measuring fish diversity and dynamics to determine fish populations in the impounded area and below the dam, assess the effects of removal on native species and the potential risk invasion by exotic fish species. Relevant stakeholders will be engaged to assess the social and economic impacts of removing the barriers. If proven feasible, removing these barriers would restore connectivity in approximately 50 km of the Côa River and Massueime Stream, including recovering the connectivity of both rivers with the Douro.

This project also aims to advance dam removal in Portugal, raise awareness of its need and disseminate guidelines on replicating it in other catchments and therefore contribute to meeting national targets for the EU Restoration Law and the Water Framework Directive.