MARE researcher demands transparency over Girabolhos Dam decision
Researcher Pedro Proença Cunha (MARE|ARNET, University of Coimbra) raises doubts over whether the Government had all the technical and scientific evidence it needed when it decided to move forward with the Girabolhos Dam.
In an opinion piece for Jornal Público, the researcher points out that the Minister of Environment and Energy has publicly referred to only one of the independent studies commissioned by the Portuguese Environment Agency (APA) following the floods that hit the Mondego basin in February 2026.
The three reports, submitted to APA on May 15th, came from separate sources. The first was drawn up by five engineers appointed by the Ordem dos Engenheiros do Centro. The second, focused mainly on the Ceira river, was the work of Professor Rodrigo Maia, from the University of Porto. The third was authored by Proença Cunha himself: a 167-page document examining in detail the benefits, limitations and environmental costs of the planned dam. The researcher notes that it remains unclear whether the other two studies were taken into account before the decision was announced and the tender for the project launched.
Proença Cunha places this episode within a broader pattern of territorial decision-making in Portugal. "Portugal has a tradition of solving territorial problems with concrete, and of being surprised when, years later, those problems persist in a new form. The Mondego case illustrates this pattern with painful clarity," he writes.
According to the author, the figures recorded over the past two and a half decades repeatedly contradict the assumptions behind the Mondego Hydraulic Regularisation project. That project assumed the existing dams would keep the flow in Coimbra below roughly 1200 m³/s for hundred-year events and 2000 m³/s for thousand-year events, the threshold above which the lower part of the city would start to flood. Yet four floods, in 2001, 2016, 2019 and 2026, have already produced attenuated flows between 1942 and 2185 m³/s, showing that what was designed as a thousand-year scenario is being reached or exceeded, on average, every six years.
Proença Cunha also questions what purpose this infrastructure actually serves. Girabolhos covers just 15% of the Mondego basin, a limitation that political enthusiasm tends to overlook: the rainfall recorded over that area in February 2026 would have been enough to fill the future reservoir almost instantly, exhausting its retention capacity at exactly the moment it would be needed most. Behind this weakness lies a deeper trade-off, the researcher notes: a dam built for electricity production operates with water levels kept high, while one built to contain floods needs the opposite, space available to absorb peak flows. These two logics, he writes, rarely coexist within the same project.
The piece also highlights what stands to be lost in ecological and heritage terms: this stretch of the Mondego remains one of the least altered in the entire basin, with its own biological richness and sediment dynamics that building a reservoir would change irreversibly. "This very negative environmental cost exists, it is measurable, and it deserves to be explicitly factored into the equation," the researcher stresses.
The researcher concludes that a decision of this scale cannot rest on hydraulic engineering criteria alone. It should draw on, among other fields, geomorphology, ecology, environmental impact assessment, landscape heritage, risk management, and social and economic factors. For the process to be credible, he argues for three requirements: full disclosure of the studies carried out, guaranteed access to information held by entities such as APA, and active involvement of municipalities, the scientific community and civil society in the final decision.
Text: Patrícia Chaves