Pre-demolition project for the removal of consecutive barriers in the Tajuña River, Spain

A project aimed at preparing and facilitating the future demolition of three weirs, thereby reconnecting nearly 13 km of river stretch in the main tributary of the Tagus basin.


The Tajuña River, the second longest in the Tagus basin, flows through the interior of Spain. The section containing the three weirs is classified as a “Mediterranean calcareous mountain river” (R-T12) within an 86.56 km long water body that remains permanent and naturally unregulated by large reservoirs. This stretch, protected by the Natura 2000 Network, is surrounded by forests of oaks, holm oaks, and gall oaks, and features riparian vegetation primarily composed of poplars (Populus nigra) and willows (Salix sp.). It supports various aquatic species of interest, including vulnerable fish such as common trout and several endemic cyprinids like the common barbel, chub, boga, and chub.

At a glance

Project typeDam removal: pre-demolition
Project statusLive
Km to be opened18
Focal speciesSalmo trutta, Luciobarbus bocagei, Achondrostoma arcasii, Pseudochondrostoma polylepis, Squalius pyrenaicus

Project context and opportunity

The three weirs presented in this project are obsolete and were abandoned decades ago, yet they continue to seriously impact the river ecosystem. These weirs fragment the habitat of protected native and endemic species, disrupt the transport of water and sediments, and alter the hydrogeomorphology of the river both upstream and downstream. The project is supported by the managing body of the hydrographic basin through the Environmental Management Area of the Tajo Hydrographic Confederation (CHT), which has cooperated in the selection and characterization of the barriers to be eliminated and will collaborate in drafting the technical projects in this phase. Additionally, the regional administration, which has the authority to evaluate demolition projects’ environmental impact, supports the proposal.

Project aims

The demolition of the three barriers will restore the natural dynamics of 12.8 km of the river in good ecological condition upstream of the La Tajera reservoir. This will facilitate migratory movements and genetic exchange of species, improve habitat conditions, and rectify negative impacts on hydrogeomorphology, promoting the creation of differentiated habitats key to biodiversity. Reestablishing ecological connectivity will directly contribute to the conservation of the fish farming community, enhancing its resilience to the effects of global warming already impacting the area.

The project includes several activities, beginning with an information, consultation, and participation process to gather local opinions about the infrastructure and its potential dismantling. This will involve meetings, educational, expository, and participatory sessions. Concurrently, technical projects for dismantling the three dams will be prepared, including studies on river topography and sediments, hydrological and hydraulic conditions, potential environmental impacts and corrective measures, monitoring and surveillance, and economic budgets. The project will integrate recommendations and conditions from competent administrations regarding future demolition authorizations and consider feedback from the participation process, incorporating proposals for preventive and corrective measures to ensure social acceptance of the demolition projects.