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18 March 2025
How are reservoirs in Spain managed during heavy rainfall?
Managing reservoirs during periods of heavy rain helps regulate water flow, prevent flooding, and optimise hydroelectric power generation. Monitoring systems, regulations, and coordination between agencies ensure efficient and sustainable water use.
Mequinenza hydroelectric power plant (Zaragoza).
1. How are reservoirs managed during heavy rainfall?
2. How do we know when a reservoir has reached its limit?
3. Who manages reservoirs in Spain?
4. What risks can heavy rains pose to reservoirs?
5. What are the benefits of increased water flow in reservoirs?
6. The importance of reservoirs in water management in Spain
Effective reservoir management ensures the safety of nearby communities, the supply of drinking water to key facilities, and the proper functioning of the hydroelectric power system. But how are they managed when it rains heavily?
How are reservoirs managed during heavy rainfall?
When rainfall causes river flows to rise, safety and system balance become the top priorities: water releases are regulated to prevent flooding while keeping water levels within established safety thresholds.
How is this done? If water needs to be released, it is done gradually by adjusting the opening of spillway gates and hydroelectric power plant turbines to avoid sudden impacts on river flow.
Water storage in reservoirs is also carefully adjusted to avoid potential overflows. To that end, real-time monitoring systems are used to track water levels and forecast flow behaviour based on weather predictions.
Coordination among the responsible authorities is key to ensuring that water releases are safe and do not pose risks to nearby communities or river ecosystems.
Water is released gradually by adjusting the spillway gates and turbines of hydroelectric power plants.
How do we know when a reservoir has reached its limit?
A reservoir’s capacity limit refers to the maximum volume of water it is designed to hold, usually measured in cubic hectometres (Hm³). This figure depends on the specific infrastructure and is defined in the dam’s technical design and operational guidelines.
We know when it’s full thanks to sensors and automated measurement systems that continuously monitor water levels in real time.
Control centres monitor river flows, reservoir levels, and electricity generation. If necessary, they adjust generation based on the needs of the electricity system and official directives—ensuring safety, sustainability, and efficiency.
Talarn hydroelectric power plant (Lleida).
Who manages reservoirs in Spain?
Reservoir management in Spain is handled by different entities that operate in coordination: the Ministry for the Ecological Transition and the Demographic Challenge (MITECO) sets national water policies, oversees planning, and regulates water use based on availability and the country’s needs.
River basin authorities are autonomous agencies under MITECO that manage water resources within each hydrological region. They regulate reservoir levels, oversee infrastructure maintenance, and control water use for consumption, irrigation, and hydroelectric power production.
At Endesa, we manage the water in our reservoirs in close coordination with these river basin authorities.
What risks can heavy rains pose to reservoirs?
A sudden increase in river flow due to heavy rain can lead to flooding in low-lying areas if not properly managed.
Effective collaboration between basin authorities and companies managing the reservoirs is essential to regulate water releases. What do we achieve with these actions? Minimise impacts on the environment and nearby communities.
Prioritise people’s safety and the protection of ecosystems.
What are the benefits of increased water flow in reservoirs?
One key benefit is greater water availability for human consumption, agricultural irrigation, and industrial use. Storing reserves during periods of abundance helps secure water supply during droughts and supports more efficient use of this essential resource.
Reservoirs equipped with hydroelectric power plants can optimise electricity generation when water volume increases. This allows them to leverage the available flow for renewable energy production.
From an environmental perspective, higher water flow can help restore wetlands and stabilise rivers—enabling aquatic flora and fauna to thrive under more favourable conditions.
The increased water volume stored in reservoirs makes hydroelectric power generation more efficient.
Susqueda dam (Girona).
The importance of reservoirs in water management in Spain
Reservoirs ensure a reliable water supply for the population and mitigate the impact of extreme weather events, such as torrential rains or prolonged droughts.
Thanks to the combination of advanced technology, hydrological planning, and efficient inter-agency coordination, we’re able to optimise the use of this vital resource.
