Rivers without Barriers

Sociedad Ibérica de Ictiología (SIBIC)

Centro Ibérico de Restauración Fluvial (CIREF)

Asociación Ibérica de Limnologia (AIL)

Asociación para el Estudio y Mejora de los Salmónidos (AEMS – Ríos con Vida)

Asociación Galega de Investigadores da Agua (AGAIA)

Sociedad Española de Ornitología (SEO/Birdlife)

World Fish Migration Foundation (WFMF)

World Wildlife Found (WWF)

The rivers in the Iberian Peninsula have more than 1230 large dams and several thousand small dams and weirs, built for a variety of purposes, that have promoted the economic development of our society for centuries. The dams and the weirs are instrumental in allowing us to exploit both the power (e.g. watermills, ironworks, fulling mills, hydroelectric power stations, etc.) and the water from the rivers (e.g. drinking water, irrigation systems, industrial purposes, etc.). Nevertheless, we need to be aware that scientific evidence has showed that dams and weirs act as barriers within rivers, and have several negative effects on the aquatic plants and animals as well as on the functioning of the river ecosystems. They also impact several ecosystem services to society such as water self-purification, natural flood control, and microclimate and/or landscape stability that are particularly valued in more arid regions.

Given this apparent conflict, society must move towards a balance between hydroelectric exploitation and river ecosystem functioning (to the extent possible), and based on well-grounded scientific knowledge. Changes in current river management strategies and plans must be made to achieve this balance, making use of the large amount of information available on river ecosystem functioning and on the high predictive power of its dynamics. Based on this knowledge, specific actions should be developed and implemented to minimize the negative effects of the barriers posed by dams and weirs on the fauna (and particularly on the fish), flora, habitats, river flow and river morphology. Such actions include fish passages, the maintenance of environmental flows, habitat recovery, etc.

Plans to remove dams and weirs should be developed for those structures reaching the end of their lifetime or their concession period, given the associated benefits of dam/weir removal towards river ecosystem functioning as well as to the reduction in maintenance costs and in the risks that abandoned or old dams and weirs pose to society. Dam removal allows the re-establishment of natural flow regimes and of physical and chemical connectivity along rivers (e.g. in temperature, oxygen), while trapping and accumulation of fine sediments upstream the dam/weir and erosion of downstream areas also ceases. Thus, rivers are allowed to regain their natural hidromorphological dynamics of sediment transport and distribution, which also promote the recovery of the natural river habitat diversity and its fauna and flora.

Improving river connectivity through dam/weir removal enables fish and other aquatic species to re-establish their natural movement behaviors associated with feeding and with the search for habitats providing shelter/protection or optimal breeding conditions, while also facilitating colonization of unoccupied areas. Several native migratory species in the Iberian Peninsula (e.g. salmon, eel, shad, lamprey, etc.) are affected by the barriers imposed by dams and weirs, and some of them have been driven to extinction (e.g. sturgeon).

Removal of dams and other barriers in rivers also avoids risks associated with their abandonment or collapse, reduces maintenance costs of obsolete structures, and above all it reduces the risks of floods upstream the dams.

Based on all the above considerations, the signatory entities request an action by the authorities and other stakeholders involved water management towards restoring the ecological connectivity in rivers, and support this statement and the immediate implementation of the actions proposed herein regarding the improvement of the physical connectivity within rivers and, particularly, the removal of all river barriers.

Signatory societies