Mértola Braces for Rising Guadiana Flows After Storm-Driven Dam Releases

Controlled Dam Releases Trigger Rising Guadiana Near Mértola

Heavy rainfall over the past 72 hours prompted the Agência Portuguesa do Ambiente (APA) to open the spillways at the Alqueva, Pedrógão and Chança dams, leading to a notable rise in the Guadiana River downstream of Mértola. Authorities warn residents to steer clear of riverbanks and remain alert for potential road closures as water levels continue to climb.

Storm Rainfall and Spillway Activation

According to data from the Instituto Português do Mar e da Atmosfera (IPMA), many parts of the Alentejo recorded between 80 mm and 140 mm of rain between last Wednesday and Friday. The Pedrógão dam’s level approached 85% capacity by Saturday morning, while Alqueva and Chança reached 90%.

Under legally mandated protocols for flood control, the APA authorised controlled releases to protect dam integrity and downstream communities. Spillway gates at Pedrógão opened at 10 m³/s on Saturday evening, followed by Alqueva at 15 m³/s and Chança at 8 m³/s. Cumulative outflow now exceeds 33 m³/s, accelerating the Guadiana’s rise below Mértola.

Official Statements and Projections

“We anticipate water levels at Mértola to increase by up to 1.5 metres over the next 24 to 36 hours,” said Ana Santos, regional director of APA. “These measures, though disruptive, are essential to avoid uncontrolled flooding and safeguard the structural stability of the dams.”

Proteção Civil Nacional has issued an orange alert for the Guadiana basin. “Our teams are monitoring river gauges around the clock,” explained Luís Ferreira, district commander for Proteção Civil in Beja. “We urge residents to follow safety guidelines and be prepared for possible road closures, especially along EN123 and local access roads near the river.”

Impact and Safety Measures

Avoid Riverbanks and Flood-Prone Areas

• Do not approach the Guadiana’s banks: currents are unpredictable and debris may be carried downstream.

• Keep children and pets away from all waterways until levels return to normal.

Road Closures and Traffic Advice

• EN123 between Mértola and Pomarão could see intermittent closures; digital panels and local police will direct motorists.

• Agricultural tracks near Herdade da Amareleja are likely to flood—alternative inland routes are advised.

Emergency Contacts

• Call 112 for urgent rescue or medical assistance.

• Proteção Civil Beja: +351 284 300 700 for flooding information and local coordination.

• APA hotline: +351 217 711 600 for dam status updates.

Background on the Guadiana Dam System

The Alqueva, Pedrógão and Chança dams form part of the Guadiana water-management network designed in the 1990s to support irrigation, hydropower and flood mitigation. Alqueva, the largest reservoir in Western Europe, holds up to 4.15 billion cubic metres (m³) of water. Pedrógão and Chança, though smaller, play a critical role in moderating peak flows during intense rainfall.

In November 2002, unprecedented storm events overwhelmed spillway capacities, flooding low-lying farmlands and prompting a nationwide review of operating protocols. Since then, APA has upgraded monitoring systems and staggered releases to minimise downstream impact.

Next Steps and Timeline

Authorities expect the spillway releases to continue at current rates until river gauges downstream stabilise—likely by late Wednesday. APA will adjust outflows daily based on inflow measurements and weather forecasts. Proteção Civil will downgrade alerts once the Guadiana recedes below the 3.5-metre mark at Mértola gauge.

Residents are encouraged to stay informed via official channels: SIRENE (Sistema de Informação de Recursos Hídricos), local municipality websites, and social-media updates from APA and Proteção Civil. By following guidance and exercising caution, communities along the Guadiana can weather the current event with minimal disruption.