What are the impacts on the Tagus River, in Portugal, of the two hydroelectric projects in the Spanish dams of Alcântara and Valdecañas? Pedro Serra and Rodrigo Oliveira tell Jornal Água&Ambiente that it is necessary to negotiate flow levels that protect the interests of both countries. Otherwise, there will be damage to Agriculture and ecosystems.
There are many concerns among environmental movements, especially with regard to ecological flows, which may not be met, particularly in the Cedillo dam, in Spain. To the Jornal Água&Ambiente, Pedro Serra, former president of the Water Institute, confesses that he looks at the issue “with concern”. “Although the Spanish ensure compliance with the flow regime of the Albufeira Convention, what happened until now is that Alcântara was just a plant with ‘turbination’, without pumping, to produce turbine energy, with the water being released as far as Cedillo ( which has a relatively limited retention capacity and arrived in Portugal quickly)”, he explains. But now, the situation is a little different, “because Alcântara has a large reservoir, with around 3 billion m3which will be pumping and boosting between Cedillo and Alcântara, and the Spanish will only launch downstream when they understand that it is not justified to be in this closed circuit regime”.
“Accentuate asymmetry”
In this way, the water resources specialist understands the concerns that have been made public, which, in itself, “justifies that the Portuguese and Spanish administrations negotiate and decide which regime should be adopted, safeguarding mutual interests”, not calling into question the needs of Portugal, namely the downstream flow regime, especially during drought, “precisely where they are needed in the national part of the basin”.
If the two countries do not come to an understanding, Pedro Serra anticipates serious problems such as “the accentuation of asymmetry”, that is, in the wet season, there will be a lot of water, but in the dry season “we could have very little water and be reduced to flow rates of the Albufeira Convention”. “In the summer season, we may have less water than we have now, so it is essential that there is an understanding that, in some way, densifies the flow regime and offers some guarantees of the inflows that Portugal needs, particularly in the section between Cedillo and the confluence of the Zêzere with the Tagus in Constância (the section of the river that is most dependent on flows from Spain)”, he says. He states that Agriculture is one of the areas that could be most affected and that, if there is less water, “there is always the risk that some species that inhabit that stretch of river may suffer”, considering it necessary to take care of the needs of ecosystems.
Rodrigo Proença de Oliveira, professor at Instituto Superior Técnico (IST), in the scientific area of Hydrology and Water Resources, also admits that the two Spanish hydroelectric projects could have impacts, especially “due to the fact that there is greater water consumption” . And he explains why: “at the moment, conflicts between uses in Spain mean that, for example, Agriculture cannot increase its consumption because it has impacts on water and hydroelectric production. By having this pumping capacity, Spain will be able to increase water use, without this having such a large impact on energy production.” Therefore, the concerns in relation to Portugal, he emphasizes, are not so much the projects themselves, but the fact that they allow for an increase in water consumption in Spain for water consumption and, at a certain point, less water reaches these hydroelectric plants, and if there is pumping capacity, less comes downstream (Portugal)”.
“It is essential that we defend, once and for all, ecological flows”
The academic assures that the solution involves implementing what is in the Albufeira Convention and defining the ecological flows for Portugal. It should be remembered that the document has provided for the definition of ecological flows since its signature in 1998, but since then a minimum flow regime has remained in force, which should be transitional. In the case of the Tagus River, the annual value is 2700 hm3. And, for this reason, Rodrigo Oliveira guarantees that the two countries must agree on a regime “satisfactory for both”. “It is essential that we defend with Spain, once and for all, the ecological flows provided for in the Convention. And, to do so, we can apply the same methodology that Spain uses in the upstream sections of the various basins”, he points out, referring to several technical decisions by the Spanish authorities, in several sections, which have approved ecological flows, some of which are subject to debate at the level of the justice system and authorized by the courts. “This methodology that is already applied in Spain can be replicated”, he says.
“We must reach an agreement with Spain on ecological flows. Therefore, these new ventures must comply with them. I recognize that it is not simple, but it is possible”, insists Rodrigo Oliveira, who agrees with Jaime Serra regarding the most direct impacts on Agriculture (with difficulties in capturing irrigation perimeters) and ecosystems.
It is recalled that on November 30, 1998, the Luso-Spanish Convention was signed in Albufeira (Algarve)., who inherited the same name. This bilateral cooperation instrument regulates the protection of the waters of the river basins shared between Spain and Portugal, of the Minho, Lima, Douro, Tagus and Guadiana rivers, also promoting the sustainable and coordinated use of their waters, taking into account the interests and peculiarities of both countries. The Convention has been an instrument in coordinating and adapting planning instruments for shared basins, especially in matters such as hydrological planning or flood risk management. It was improved in 2008, through the introduction of some improvements to the flow regime.
