A disused weir comes down in Spain's Cantabria, freeing 24 km of river for salmon

A disused weir that blocked salmon on a river in northern Spain has been partly demolished, opening about 24 km of river upstream to migrating fish, elDiario.es reported on 26 October. The work on the Valverde weir, on the Bullón River in Frama, Cabezón de Liébana, in Cantabria, was carried out by the local conservation association Red Cambera.

A 1.7-meter wall from a closed fish farm

The stone and masonry weir was about 1.7 meters high and spanned 24 meters between the banks. It once fed water to the Frama fish farm, which had been abandoned for years and officially dismantled, and it no longer had an operating concession. Its central fish pass did not work, and the drop of about 1.5 meters between water levels made it “practically impassable” for fish such as salmon, the association said.

On the advice of the Cantabrian river basin authority, the Confederación Hidrográfica del Cantábrico, 14 meters of the structure were taken out. Besides the 24 km upstream, the work reconnects about 42 km of channel downstream. The Bullón is part of the Deva basin, and this is Red Cambera's fifth demolition there since 2021, according to the report.

Paid for by a European dam removal fund

The project cost €83,228 and was funded by the Open Rivers Programme, which gives grants for removing small dams and restoring river flow and biodiversity across Europe. Before the work, Red Cambera ran feasibility studies, drew up technical plans and obtained permits from national, regional and local authorities. Noel Quevedo Aja led the initiative for the association. The programme, funded by the foundation Arcadia, is especially interested in projects that let at least 10 km of river flow freely again, and it recently backed 33 new projects in its 13th grant round, according to the Open Rivers Programme.

Spain is among the leaders in clearing old barriers

Europe's rivers are fragmented by roughly 1.2 million barriers, more than 150,000 of which are considered obsolete, according to Wetlands International Europe, Mongabay reported. Nearly 2,300 dams have been removed across Europe since 2020, mostly in Sweden, Finland and Spain, and 603 barriers came down in 2025 alone, reconnecting more than 3,740 km of river, according to the Dam Removal Europe report.

Removing a barrier does not by itself bring fish back, which is why the next step on the Bullón is monitoring. Over the coming months, Red Cambera will run a monitoring plan with a set scientific method, studying the river and the weir's impact before, during and after the demolition, to judge in the medium and long term whether the project worked. In the United States, Chinook salmon reclaimed 88% of their old Klamath River range within two years of the dams there coming down.