Tama Dam, Spain

Introduction

The source of Deva River is in Fuente Dé (Cantabria), more than one thousand meters in altitude and 62 kilometres long until its mouth in the Tina Mayor estuary. Throughout its course, it crosses eight municipalities, occupying an area of 648.207 km2 and supporting an average annual flow of 10 m3/s. The Tama Weir is located in the middle course of the Deva River.

The fluvial course is part of various environmental protection areas, including a national park, a Special Protection Area of Birds, a Special Area of Conservation and a Natural Monument area.

Project context and opportunity

Hydraulic infrastructures in the Deva River basin fragment the fluvial ecosystem and disrupt water flow, material transport, energy dynamics, and the movement of aquatic fauna, limiting their habitat range. Of particular significance is the Tama Dam, which, stands as the primary barrier for migratory fish in the Deva River. It is an impassable obstacle because it lacks a fish ladder to aid fish passage.

Removing the Tama Dam is a crucial opportunity to restore river continuity, subsequently revitalising the biological and physical diversity of the fluvial ecosystem. Additionally, this restoration aligns with the hydromorphological criteria outlined in the Water Framework Directive (2000/60/EC).

This demolition is expected to expand the distribution areas of numerous species in the Deva basin, especially those of community interest, such as Salmo salar and Petromyzon marinus, along with other culturally significant species like Salmo trutta. Enhancing the population dynamics of these species will also benefit other community-relevant aquatic species like the kingfisher and otter. Moreover, the demolition is expected to restore the Deva River’s natural sediment dynamics and contribute to the region’s overall ecological and landscape health.

Project aims

This project will focus on the pre-demolition work needed to finally remove the dam. The main objective of this demolition is to improve the longitudinal connectivity of the river network of the Deva basin, demolishing a hydraulic infrastructure that is currently in disuse and without an exploitation concession.

With this, the following specific objectives are expected to be achieved:

1. Restoration of a favourable conservation status of the aquatic habitats and species of Community Interest (those included in Annex I, II and IV of the Habitats Directive).
2. Reaching a favorable conservation status of Salmo salar, Petromyzon marinus, Austropotamobius pallipes and Galemys pyrenaicus, in the Atlantic Spanish region.
3. Improvement of habitat and reduction of risks for five species of CI (earlier mentioned) through eliminating pressures that reduce their population numbers and migration capacity.
4. Avoiding the isolation of confined populations due to the effect of anthropogenic infrastructures or the absence of appropriate ecological corridors that facilitate their dispersion.
5. An improvement is expected in alder and ash riparian forests (priority habitat 91E0*).

Project achievements

In October 2023, the successful removal of the Tama weir achieved the project’s goal of restoring river connectivity in the Deva River basin. This work has opened 27 km of the main channel toward the Deva River and an additional 25 km along the Bullón River, a significant tributary.