With scientific field coordination provided by CESAM/DBIO researchers Nelson Abrantes and João Pestana, CESAM is leading the Study to Assess Environmental Impacts resulting from the accidental discharge into the River Lis. The investigation has been under way since early September and aims to characterise, with scientific rigour, the effects of the incident that occurred on 12 August at the B7 Pumping Station (EEB7).
Since the start of the campaign, the CESAM team has been in the field collecting samples at 10 strategically defined sampling points upstream and downstream of EEB7, including agricultural drainage channels (valas hidroagrícolas). This sampling design will enable assessment of the condition of the water bodies and the analysis of multiple ecological descriptors: ichthyofauna (abundance, biomass, indices; and assessment of mortality and population structure), benthic macroinvertebrates and diatoms (with substrate collection and taxonomic analysis).
The sampling process has been accompanied by the operational team and specialists from the Águas do Centro Litoral (AdCL) laboratory, whose scientific support benefits from in-depth knowledge of the study area. Preliminary results indicate that the water quality of the River Lis shows no signs of degradation.
The study objectives include: assessing the condition of potentially affected water bodies (the River Lis and hydro-agricultural channels); identifying and quantifying impacts on aquatic communities (ichthyofauna, benthic macroinvertebrates and diatoms), water quality and sediments; delineating the affected area and the temporal extent of impacts; and supporting the definition of follow-up monitoring, ecological recovery and environmental damage compensation measures. These results will underpin the Impact Assessment and Minimisation Plan that AdCL intends to implement to strengthen the resilience of the wastewater system and prevent future occurrences.
The mission is being carried out by a multidisciplinary CESAM team, which will present the actions undertaken and preliminary conclusions at the meeting of the Monitoring Committee for the EEB7 Emergency Discharge, to be held on 21 October. This Committee includes the Secretary of State for the Environment, the Portuguese Environment Agency (APA), the Municipal Councils of Leiria and Marinha Grande, CIMRL, the Association of Irrigators and Beneficiaries of the Lis, the Parish Councils of Vieira and Monte Real/Carvide, and AdCL. The initial conclusions will be consolidated in a preliminary report to be shared with the Committee, in line with the commitment to transparency and coordination made from the outset.
The final study report will be delivered at the end of the year. Once the affected area has been delineated and the integrated assessment (biological, chemical and ecological) completed, as well as the identification of direct impacts and affected parties, a follow-up monitoring plan will be proposed and remediation and ecological recovery measures implemented.
Original news: Águas de Portugal website, 25 September 2025.