On 28 April 2025, a sudden, large-scale power disturbance originating in Spain’s transmission grid triggered a cascading blackout across mainland Spain and Portugal, with limited impact on southwestern France. The event caused an abrupt 10 GW drop in grid load, disrupting electricity service for several hours and significantly affecting critical infrastructure, including water supply and wastewater systems.
Water utilities across urban and rural areas reported supply interruptions, pressure losses, and degraded service. Recovery times varied depending on the availability and performance of backup systems. Although grid power was restored within 24 hours, the incident exposed the fragility of water infrastructure under energy stress, raising critical questions about system resilience amid growing electrification and climate risks.
The timing of the event helped to mitigate its worst effects. Taking place during a period of moderate electricity demand and healthy hydrological reserves, hydroelectric power plants played a key role in stabilizing the grid during recovery. Reservoir levels at 76.4%, an exception from recent drought conditions, enabled the rapid dispatch of hydropower, which surged from 2.0% to 35.0% of the mix over 24.0 hours.
