Tagus: Iberdola’s operation in Spanish dams threatens flows in Portugal | Water

The ecological flow regime on the Tagus River once again raises the concerns of environmentalists, social and cultural organizations and local authorities “in the face of the risk” that could come to fruition with the installation of a reversible hydroelectric pumping system in the Spanish dams of Alcântara and Valdecañas”, concessioned to Iberdrola. In response to PÚBLICO, the Ministry of the Environment highlights that regularization in the Tagus basin, both in Spain and Portugal, implies the definition of ecological flow regimes that guarantee the maintenance of the various functions added to the river, namely the good condition of the masses of water.

A group of 25 Portuguese and Spanish organizations signed the complaint by proTEJO – Movimento pelo Tagus, which was sent to the European Commission on March 18. The document expresses the fear that the project will “limit water inflows” into the river Iberian, in Portuguese territory.

Subsequently, on April 18, the proTEJO movement “alerted”, through an open letter sent to the Minister of Environment and Energy (MAE), Maria da Graça Carvalho, of the “urgency to demand” from the Spanish authorities the implementation of ecological flows in the Cedillo dam on the Tagus River.

In that letter, the proTEJO movement admitted that the completion of the Iberdrola project could “significantly worsen the availability and variability of flows in the Tagus River” as a result of the restriction of water flowing to Portugal from Spain. And he adds “no more than the minimum flow volume limit of 2700hm3, and perhaps a drop more, should be expected to formally comply with the Albufeira Convention, similar to what happened in the few years of drought that devastated the Tagus River” .

Therefore, and taking into account that, on average, more than double the minimum annual flow rate foreseen in the Albufeira Convention (around 5500hm3) has arrived from Spain, the open letter sent to the MAE says that “there is a risk that every year hydrological periods become years of artificial drought”, sending only 2700hm3 of minimum annual flow.

The proTEJO has already warned and appealed to the municipalities of the Tagus basin, its inter-municipal communities (Lezíria do Tejo, Médio Tejo, Beira Baixa and Alto Alentejo) and the Lisbon Metropolitan Area (AML), to take a responsible position demanding that governments of Portugal and Spain to implement an ecological flow regime in the Cedillo dam on the Tagus River.

Ensuring the functions of the river

PÚBLICO asked MAE to comment on the content of the PROTEJO letter on the ecological flow regime on the Tagus River.

MAE source recalled that the Albufeira Convention agreed for the Cooperation, Protection and Sustainable Use of Waters in the Luso-Spanish Hydrographic Basins “requires a flow regime, which requires compliance with a minimum annual volume, in line with community provisions and national in this matter”. And, in the case of the Tagus basin, “it also establishes a minimum quarterly and weekly volume”.

The MAE’s position makes it clear that the regularization currently taking place in the Tagus basin, both in Spain and Portugal, “implies the need to define ecological flow regimes (ECR) that ensure the maintenance of the various functions added to the river, namely the good condition of water bodies”. And he explains that the border area is characterized by a set of three dams in a cascade – Cedillo, Fratel and Belver – and, in this sense, “the release of ecological flows must be reflected in the last dam of the cascade, through the upstream inflows” .

Comparatively and referring to the current state of the basin in Portuguese territory, the guardianship uses data from the Portuguese Environment Agency (APA): “ecological flows are being released in the Castelo do Bode and Pracana dams”, and concludes that , within the framework of the current convention, “continuous coordination work is carried out (in terms of planning, management, surveillance, alerts and improvement of mechanisms for complying with the current flow regime) and adaptation of the ecological flows to the requirements of the Water Framework Directive”.

The APA also warned that the implementation of the Spanish project “could be likely to cause significant environmental effects in Portugal”. To gather more information, APA notified Spain of its interest in participating in the Assessment of Environmental impact (AIA). In their response, the Spanish entities guarantee that the new project “will produce a moderate environmental impact”, and that the effects on the Natura 2000 Network “can be minimized”.

The proposal for the Tagus basin

The proposal that the movement defends for the hydrographic basin of the Tagus is based on the establishment of regular, continuous and instantaneous ecological flows, measured in cubic meters per second (m3/s) for dry, medium and wet years, respecting the seasonality of the seasons, that is, higher in winter and in autumn and smaller in summer and spring. This claim intends to contradict the criterion followed, which is based on “minimum flows negotiated politically and administratively 25 years ago in the Albufeira Convention without the transition process to the ecological flow regime that that same convention envisages having ever materialized”.

The non-establishment of ecological flows, adds the proTEJO position, “has allowed for extreme volatility in flows received from Spain, which harms ecosystems and water uses”, namely agricultural uses and “non-compliance with the Water Framework Directive ”.

The problem results from the “great volatility of flows from hour to hour and day to day allowed by quarterly flows”, which represent 37% of the annual flow, and weekly flows, which are 12% of the annual rate, an anomaly that “harms ecosystems and agricultural uses and already caused water salinity problems for irrigators in Vila Franca de Xira”, adds the movement.

On April 25th, the implementation of an ecological flow regime on the Tagus River through negotiation with Spain was defended by professor Rodrigo Proença de Oliveira, from the Instituto Superior Técnico (IST), responsible for studying water availability in Portugal, in which based the 2022-2027 watershed plans.

To PÚBLICO, the professor highlighted: the reversible system planned for the Alcântara and Valdecañas dams is already installed in the Portuguese dams of Alqueva, Tâmega, Aguieira and Raiva, and will appear “in a few years” in the structuring of Spanish hydroelectric systems – “they will resort to photovoltaic energy that is produced in excess” and return to the dams the water that was turbocharged to function as a species of water stock depending on “market needs”, as highlighted in the “Assessment of Current and Future Water Availability”, prepared for the Iberdrola project.

It works “partially” in a closed circuit, releasing a greater volume of water upstream than is sent at present, “alleviating consumptive uses [com vários usos, além da produção de energia eléctrica]”, says Proença de Oliveira, stressing that the change will certainly “please” Spanish farmers. They now have access to more water for irrigation and livestock farming, alleviating the tension that exists between farmers and Iberdrola.

The consequences of installing this process in the Cedillo dam, located on the border, could result in a smaller volume of water for Portugal and the degradation of riverside ecosystems.

Worried mayors

Concerned about the functioning of the reversible system in the two Spanish dams, the mayors of the municipalities of Castelo Branco, Idanha-a-Nova, Oleiros, Penamacor, Proença-a-Nova, Sertã, Vila de Rei and Vila Velha de Ródão defended and deliberated in the Last Thursday, May 2nd, it is “necessary and urgent to scientifically clarify the ecological flow regime, in both countries, applicable to the Tagus River”.

His attention focuses on the “more than likely reduction in the flow of the Tagus River, from the Cedillo dam”, explaining that the use of the reversible system “imposes a level quota of the water plane in this reservoir that makes it viable elevation and reuse”. This operation, stress the mayors, will allow the use of water in a closed cycle, “without the production of energy in Alcântara meaning a transfer of flow without return, to Portuguese territory, with damage, in this case, to Portuguese reservoirs and to the environmental structure associated with the river, downstream”.

Regarding transboundary impacts, the document that makes the “Assessment of Current and Future Water Availability” notes that “a potential impact on riverine habitats of community interest (HIC) present on the banks of the Cedillo reservoir was detected”. This scenario will be a “consequence of the drop in the level of the reservoir to level 100 during the execution of the works (five months during the external excavation and construction of cofferdams for the installation of the lower water intakes, and another five months during the removal of the cofferdams and bed cleaning, in non-consecutive years).