Nalón River, Spain
Ness River, United Kingdom
August 15, 2017


The University of Oviedo leads an AMBER case study on the Nalón River. The dams in the system provide essential services but also threaten biodiversity and sites of cultural importance. University of Oviedo will use eDNA to monitor various species and assess social variables related to dams and reservoirs.

Area in economic decline


Nalón River, located in the central part of the province of Asturias (Bay of Biscay, North Iberia, Spain), belongs to the largest basin of this region. The area is in economic decline due to the closure of coal mining and the abandon of agriculture/husbandry activities after the entrance to the EU common economic space in the 80s. The Nalón valley shelters the most famous mining zone of the region, especially in the middle part of the river. This part was and still is degraded.

The Cantabric Hydrographic Confederation has carried out several restoration programs in the river valley and main tributaries. The water quality has improved in the middle zone in the last decade but is still bad downstream, where the river hosts numerous species of exotic fish. Archaeological excavations on Neanderthal sites are carried out in the valleys (i.e. Cueva del Conde, Trubia stream). Upstream tributaries are located inside protected spaces, such as the UNESCO (United Nations Educational, Scientific and Cultural Organization) Biosphere Reserve and Natural Park of Redes (a Site of Community Importance, and a Special Protection Area for migratory birds with three natural monuments as well). Besides the exotic fauna, Nalón River holds an aquatic biota composed of a variety of high interest species as the Eurasian otter, the Pyrenean desman (Galemys pyrenaicus), catalogued respectively as near threatened and vulnerable by IUCN 3.1 (international Union for the Conservation of Nature 2016). Amphibians, such as the classified vulnerable, Iberian endemic fire-striped salamander (Chioglossa lusitanica), find numerous water sources to live such as drinking troughs and old fountains. There are also abundant groups of invertebrates (an essential part of the trophic chain) and four fish species including brown trout (Salmo trutta) and the European eel (Anguilla anguilla), almost extinct in the zone due to the dams. Several elements of cultural heritage catalogued as ‘Bien de Interés Cultural (BIC)’ (translated ‘Patrimony of Cultural Interest’), a special category of heritage patrimony in Spain, are situated in the Upper Nalón. Amongst them there is one located in Caleao, where the new reservoir is projected.


Problem description

There are seven dams interrupting connectivity along the river system. They were built principally in the 60s & 70s and have diverse uses: water supply, hydro-electrical power, control of flood risks, recreational activities (fishing, canoeing). Two of them have fish passages (Furacón and Valduno), and one small weir (El Machón) was demolished in 2013. In addition, a new dam (in Caleao) is projected upstream for water and energy supply, and for compensatory flows to maintain biodiversity (enhancing water quality for salmonids downstream).


  • Dam construction
  • Habitat loss
  • Habitat alteration

    Stakes & stakeholders

    The projected dam construction promoted by the Regional Government of Asturias, the Asturias Water Consortium and CADASA has been much contested by ecological and conservationist associations (Ecologistas en Accion, at Spanish national level; Asociacion Asturiana de Amigos de la Naturaleza (ANA); SEO-Birdlife.) because it will affect the protected area previously cited (Natural Park of Redes) and several protected species within. The different stakeholders maintain an open conflict since 1992 when the dam project was declared of national interest (RDL 3/ 1,992 of 22 May, BOE 27 May 1,992).

    EDP-Energía (international company) manage the main reservoirs present in Nalón River. Fishermen associations (Amigos del Nalón; El Banzao; Real Asociación Asturiana de Pesca) participate in river management (i.e: being in charge of Brown trout supportive breeding).

    There are also some local stakeholders like the Asociación de Comerciantes e Industriales del Valle del Nalón (ACOIVAN); Asturcentral (association of rural tourism); councils of Caso, San Martin del Rey Aurelio, Trubia, Santo Adriano de Tuñon, Teverga, Quiros, Proaza, Aller, who are affected by the ecologic circumstances and economic activities derived from dam’s construction, demolition or maintenance.


  • Water supply
  • Hydro power
  • Flood control
  • Angling
  • Biodiversity

    Approach & tools used

    University of Oviedo developed and applied an eDNA molecular kit to assess the biota present in different hydrographic sections. This also includes the use of sequences obtained from eDNA to determine population connectivity; detect invasive species along the river and check if its presence is associated to dams, and how barriers affect their distribution; and monitor macroinvertebrate species as fish trophic resources and as bioindicators of water quality. University of Oviedo also developed and validated a questionnaire to model social attitudes towards dams and reservoirs. The implementation of this tool in some affected areas by dams and reservoirs in the region of Asturias (Caleao, Rioseco, Tanes, etc) will contribute to identifying social variables that have a great impact on the moderation of barriers.


  • eDNA
  • Questionnaire
  • Ecosystem services
  • Costs and benefits of dam construction
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