Almost half of Spain’s rivers are in poor condition due to dams, climate change and invasive species

Almost half of Spain’s rivers are in poor condition. With their courses fragmented by thousands of constructions, overrun with invasive species and devoid of riparian forest, 45% of these water bodies are degraded, according to the draft National River Restoration Strategy.

Of the 4,000 courses reviewed, more than 1,800 have a negative global status. “Despite the improvements, the environmental targets have not been met,” which were to be completed by 2021, the Ministry of Ecological Transition said in a document.

The river map of Spain shows that among the basins that cross several autonomous communities, the worst data are the Duero – 483 in bad condition 163 good, Guadiana -170 in 71 – and Jucar – 178 in 135.

Of the basins that are spread over only one community, the Catalan river basin district has 154 in poor condition and 96 in good condition. In Andalusia, the Tinto-Odiel-Piedras basin has 25 bad masses and 23 good ones.

“It’s good that there is a strategy, it’s better not to have one, but it seems insufficient, because the rivers in Spain are very affected. They are in very bad shape,” says Santiago Martín Barajas, from Ecologistas en Acción. “It’s a pretty significant leap from what it was before,” analyzes Octavio Infante, SEO-Birdlife.

When asked for examples, Martín Barajas lists almost without pause: “There is the Siurana, which is the tortured river, the Genil, which passes through Granada, the Guadalmedina in Málaga, the Zapardiel, when it reaches the Medina del Campo… They do not end: the river Viñalopo in Elche… “, he continues. There are 100,000 kilometers of rivers in Spain and they are not good at all.

River restoration involves restoring rivers as rivers: restoring their ecological integrity and ecosystem services. And this “requires the elimination, modification or management of all pressures that alter it and deviate from its original state,” the strategy states. “The community demands the restoration of the river and will not tolerate acts of degradation,” he says.

But what is affecting Spain’s rivers? “National-level land-use changes, stream modification, and invasive species proliferation.”

In addition, Infante also focuses on the “invisible”, such as diffuse pollution diluted in water. “It’s not easy to discuss, but it’s very important” and applies to sectors such as agriculture and the pharmaceutical industry. Infante explains that “Nicotine and caffeine are two indicators of how far people go, and the amount of these compounds found in rivers is incredible.”

The large number of structures that cut rivers is one of the most important aggressions caused by human activity, the project notes. In the analysis of the Ministry, it is called “the change in the continuity of the longitudinal flow”. There are still 18,500 barriers – “transverse works” – in the form of dams, dams and culverts.

To this must be added another 14,000 lateral obstructions, which are usually walls, ridges or breakwaters built with the idea of ​​preventing the flow of water or stabilizing the banks.

WWF’s Europe-wide study concluded that around 50,000 kilometers of river flows could be freed up on the continent, 17,000 of them in Spain, if these obstacles, which they called “permanent litter”, were removed.

what causes

The fragmentation of rivers by these barriers means fragmentation of habitats “with a very negative impact on migratory fish” but also leads to “an imbalance in sediment transport”. To understand this, it is enough to look at the Ebro delta, which has remained vulnerable to the storm of the sea, because these sediments do not reach it.

Lateral dams prevent the flow from moving to the sides, which changes its course, making it impossible for water to reach the banks or floodplain ecosystems (a Donana marsh is a marsh from which water does not receive water from rivers. , only from rain).

Spain’s rivers – and reservoirs – are teeming with invasive alien species. Both plant and animal. “The introduction of invasive species poses a threat to river ecosystems,” describes the strategy.

There are well-known cases such as the “spread” of the zebra mussel, which affects the water supply network or the Camalotti factory, which forced the investment of more than 50 million euros in just one shock plan for the Guadiana.

In addition, of the 18 river fish species classified as “invasive”, 15 are species associated with sport fishing (either because they were introduced as trophies or because they were released as food for the former). A legal modification approved in 2018 by PP, PNV, Ciudadanos and PDeCAT allows all these species to be kept where they were before 2007, despite the ecological damage, sometimes “devastating”, they continue to cause.


Each species has its own effects, but in general “causes very significant losses both economically and in biodiversity”.

For example, fishing trophies are usually predatory species that, according to files in the Spanish catalog of invaders, have caused “local extinction” of the populations they prey on. For this reason, anglers turn to the “grass” species released in the rivers to eat the trophies. Some of them are also invasive species.

Water hyacinth is so bushy that it blocks sunlight and reduces dissolved oxygen in the water, causing “devastating” effects on aquatic life. It also “reduces water available for irrigation and human consumption” and promotes mosquito breeding.

The context of the climate crisis has a direct impact on Spain’s rivers. Scarce, more torrential and accumulated precipitation in less time will cause rivers to “change their temporal regime, moving from permanent to seasonal and from seasonal to ephemeral”. And it’s not a harmless process, the document explains, but it will lead to “changes in biogeochemical cycles and loss of biodiversity.”

Riparian vegetation offers a first line of defense in the face of climate change, but it is under attack from “water catchments, flow regulation, livestock and agricultural use, and the presence of invasive exotic species.”

what causes

Its reduction or disappearance prevents it from reducing the effects of flooding and reducing soil loss due to erosion. Without these forests and bushes, the banks are destabilized and sediments pass through. In addition, riparian vegetation is able to change the microclimatic conditions of the environment, retain atmospheric carbon and mitigate the spread of forest fires. But if they are not there, these functions evaporate.

For the public to be able to access the benefits provided by rivers, courses must be in a “good state of conservation”, the strategy recalls. And he emphasizes that none of the work done in them can be called restoration. “An action cannot be considered restoration if its purpose is to change a river system for human use without improving its conservation status.”

When asked how he will expand the action of the strategy, Martin Barajas chooses a measure: “to double the 75 million budget for the renaturalization of urban stretches of rivers.” The ecologist explains: “It not only provides natural benefits, but also social ones. Cities and people need it.”

Source: El Diario





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