With this judgement, the Spanish Supreme Court has partially upheld the appeal brought by the environmental groups Plataforma en Defensa de los Ríos Tajo y Alberche and GRAMA, challenging provisions of the Hydrological Plan for the Tagus River. This plan which envisaged a staggered implementation of the ecological flow targets in 19 water bodies along the central axis of the Tagus between the Bolarque and Valdecañas reservoirs. The court emphasised that the EU requirements have been binding since 2009 and that a delay until 2027 is not permissible.

Transfer reactivated due to record rainfalls

Following an exceptionally rainy spring, operations of the Tagus–Segura water transfer resumed in full in April. The transfer delivers surplus water from the Tagus river to the Segura river basin, where it is distributed for municipal use. The fact that record rainfall fell in the area in question this spring should not distract from the fact that usually more than 50 % of the irrigated land in the Segura basin depends on water from the transfer, according to the Sindicato Central de Regantes del Acueducto Tajo-Segura (SCRATS). In general, the basin suffers from structural water scarcity and experienced several severe drought periods during the last 30 years.

More details about the effects of climate change to the Tagus-Segura Transfer are published in the study carried out by a research team of university of Alicante, Spain.

Transformation of legal and political framework

The ruling, delivered on May 6 and published in Spain’s official state bulletin on June 6, is transforming the legal and political framework surrounding the Tajo–Segura water transfer. Ecological flows refer to the minimum water levels that must be maintained in a river to preserve its ecological integrity. These flows are essential for safeguarding habitats, protecting species, and ensuring the proper functioning of aquatic ecosystems. In the case of the Tagus River, the court’s decision specifically addresses water bodies within legally protected zones, including those under the EU’s Natura 2000 network. The court determined that delaying the enforcement of these ecological flow requirements was a breach of environmental law and ruled that their implementation must not be postponed.

On June 11, Spain’s Secretary of State for the Environment, Hugo Morán, affirmed that the government will strictly implement the Supreme Court’s ruling. He indicated that the Ministry for Ecological Transition (MITECO) is actively developing measures to guarantee compliance, which may include revising water management plans and possibly updating the regulations governing the Tajo–Segura transfer system.

Leaders of southern province Murcia concerned about security of supply

Murcia’s regional authorities and irrigation unions support the continuation of the Tajo–Segura water transfer, arguing that the recent court ruling does not prohibit phased ecological flow implementation in non-protected areas and that the infrastructure remains legal. Southeastern regions, including Murcia, have protested against cuts to the transfer, while leaders in Murcia, Valencia, and parts of Andalusia warn of negative consequences from the ruling. Murcia’s water minister and other officials are considering legal appeals and criticize the ruling’s political aspects. Irrigation unions maintain that the decision only affects protected river stretches but are concerned that new ecological flow requirements may reduce future water availability.