the technical imbalance that is silently killing Spanish reservoirs
In a window of just 72 hours, Spain’s water reserve has experienced unprecedented growth. The data has gone from 693 cubic hectometers in one day, shooting up to 2,349 hm³ in just three days. However, behind this photograph of abundance and a blue-tinted map of Spain, Greenpeace has warned that we are facing an optical illusion. What we see shining in the sun is water, yes, but what accumulates at the bottom, invisible and silent, is mud. And there are more and more. The denunciation of silent death. The environmental organization Greenpeace has issued an alert: The useful life of Spanish reservoirs is running out. This is not an imminent risk of the concrete walls collapsing – the dams are sound from a civil engineering point of view – but rather what they call a “dramatic loss of operational efficiency.” The underlying problem is the calendar. The bulk of our hydraulic infrastructure was built during the dictatorship (1950-1975). This means, according to the data managed by the organization, that “a large part of the dams is now crossing the threshold of their theoretical project useful life”, estimated between 50 and 75 years. The concrete holds, but the steel mechanisms, such as valves and drains, suffer the passage of time. The physics of “solid avenues.” To understand why reservoirs are losing capacity, we must look at the violence of recent rains. As explained by the organizationthe new explosive storms fall on highly eroded basins. The water carries tons of earth, stones and debris into the reservoir. Older infrastructures lack the agility to manage this mix. The technical data is alarming. According to reports from the Ministry for the Ecological Transition (MITECO) and the CEDEX (Center for Studies and Experimentation of Public Works), the Ebro River has radically changed his behavior. Before the dams, the river transported 5.16 million tons of sediment per year to the Delta. Today, trapped by concrete walls, it only allows 0.37 million tons to pass through. The rest remains trapped, reducing the useful space for water. Chronicle of an ignored obsolescence. This is not an unforeseen accident; It is the result of managing the climate of the 21st century with tools from the mid-20th century. Greenpeace insists the dams operate under “climatic pressure for which they were not designed.” In the province of León, iconic reservoirs such as Villameca (inaugurated in 1946) or Barrios de Luna (1956) were designed under stable climatic parameters that have little to do with with the current extreme variability. Experts have been warning for years: geologists from the University of Barcelona They already warned in 2018 that the uncertainty about the real amount of sediment is high, because monitoring the bottom of all the swamps is complex and expensive. When the mud becomes a threat. This accumulation of materials is not just a capacity issue; It is a physical security risk that is already showing its most dangerous side in the south. While we celebrate the rain, a silent battle is being waged in Huelva against toxic sludge. Just a few days ago, the Military Emergency Unit (UME) has had to be deployed in “anticipation” in the mining ponds of the province. There, torrential rains—which have tripled forecasts in some areas—have saturated the terrain to the limit. The risk is no longer just that the reservoir will lose site, but also the liquefaction of the sludge: that the pressure of the water converts the solid waste into an uncontrollable tide. It is the most graphic reminder that our infrastructures, whether water dams or waste ponds, are suffering stress for which they are hardly prepared. From the dredge to the forest. If the reservoirs are full of mud, logic would dictate removing it; but the economic reality makes it unviable. CEDEX technical notes cited in the context of the Greenpeace complaint show that the cost of extracting The sediment “far outweighs the cost of preventing it.” Cleaning a small reservoir of just 10 hm³ could cost between 50 and 150 million euros. If the sludge needs pretreatment before going to the landfill, the price skyrockets. For its part, the MITECO has started “pilot tests” to mobilize sediments in the Mequinenza-Ribarroja section, with a budget of 1.2 million euros, but they are surgical interventions in a systemic problem. For Greenpeace, the solution is not in concrete, but in the mountains. “The solution does not end at the dam or reservoir, it begins in its surroundings,” they say. The organization demands an urgent hydrological-forest restoration, where a healthy riverbed and a basin full of trees act as a “sponge.” The roots retain the soil and prevent the mountain from falling apart when it rains heavily and ending up at the bottom of the swamp. The risk of illusory guarantee. The EU Nature Restoration Regulation, approved in 2024, obliges Spain to present a National Plan by August 2026. It is the last opportunity to change the strategy. Julio Barea, head of water at Greenpeace, issues a final warning that should resonate beyond the current rain: “The technical obsolescence of our reservoirs will make us increasingly vulnerable to the next great water crisis.” If the bottom drains are not modernized (so that the mud can leave) and the headwaters of the rivers are not reforested (so that the mud does not reach), the “water guarantee” will be a statistical fantasy. Image | freepik Xataka | Far from Grazalema and the reservoirs, Andalusia has another serious problem: completely collapsed mining ponds
