A prolonged blackout in Spain would not immediately affect the drinking water supply. During the first hours, the operating entities would activate backup mechanisms - emergency generators, water reserves in tanks, residual pressure in pipes - to sustain the service. However, these systems have limited autonomy. When the fuel runs out, the electric pumps stop, and the water reserves empty, the real collapse could begin: water would stop reaching the citizens.
From backup to total interruption
The first link to give in would be the water capture systems. Wells, powered by electric pumps, would stop extracting groundwater once the generator's capacity is exhausted. Similarly, surface capture stations, which pump water from rivers and reservoirs to treatment plants, would come to a standstill. Although some facilities could temporarily operate with generators, the constant diesel consumption would make their operation unsustainable within a few days.
Without active capture, the water purification plants would be left without raw material to treat. And even if there were stored water reserves, the halt in filtering, sedimentation, and chlorination processes would prevent ensuring its sanitary quality. The available water could become dangerous for consumption, invisible to the naked eye but potentially loaded with bacteria and contaminants.
The next major link would be distribution. Without intermediate pumping, the primary and secondary water networks would quickly lose pressure. Elevated and peripheral areas would be the first to run out of water. Additionally, the low pressure would allow the infiltration of contaminants from the outside, further worsening the sanitary situation.
The collapse of sanitation and the health emergency
As access to drinking water fades, the sanitation system would also enter a crisis. Wastewater treatment plants and sewage pumping stations, deprived of energy, would cease to function. This would lead to the overflow of contaminated water in streets, homes, and public areas, creating infection hotspots that would spread rapidly.
The failure of automatic chlorination systems would add another risk: the water that could still be in networks or tanks would be without disinfection, increasing the population's exposure to gastrointestinal diseases and other serious health problems. Simultaneously, the control systems that allow for remote monitoring of the network's status would be out of service, leaving operators blind just when a quick and precise response would be most needed.
Although water tanker trucks are a common strategy for delivering drinking water in emergencies, their operation also depends on loading points equipped with electric pumps. Without power, the response capacity with tankers would be very limited, leaving large urban and rural areas unattended.
Which elements of the water supply network are affected in a prolonged blackout?
What they do: Extract groundwater using submerged electric pumps.
What happens if they fail: Without power, the pumps shut down, completely stopping the groundwater extraction. Without active wells, rural communities and some urban areas depending on aquifers would quickly run out of supply.
2. Surface capture stations (rivers, reservoirs, dams)
What they do: Capture water from surface sources for purification.
What happens if they fail: Without electric pumping, water cannot be transported from the river or reservoir to the treatment plants, interrupting the purification process from the source.
What they do: Clean and disinfect raw water through filtration, sedimentation, chlorination, and other physical and chemical processes.
What happens if they fail: Pumps, valves, filtering systems, and chemical dosers require energy. A failure halts the plant, compromising the sanitary quality of the available water.
4. Intermediate pumping stations
What they do: Maintain the proper pressure in the system to transport water over long distances or to high areas.
What happens if they fail: Areas on slopes, mountains, or tall buildings lose service first, creating inequality in water access among different city sectors.
5. Potable water storage tanks
What they do: Store treated water reserves for distribution in case of high demand or contingency.
What happens if they fail: Although the tanks continue to store water, without daily replenishment, they empty in a matter of hours or days. Without power, new water cannot be pumped to replenish them.
6. Primary distribution network (main pipes)
What they do: Transport large volumes of water from purification plants to cities.
What happens if they fail: The loss of pressure in these pipes allows possible infiltration of bacteria and contaminants from the soil, compromising the entire connected secondary network.
7. Secondary distribution network (smaller pipes and branches)
What they do: Distribute water from the primary network to homes, businesses, and hospitals.
What happens if they fail: Low pressures cause supply interruptions in homes, hidden leaks, and the entry of contaminating agents, making the water that could come out of the taps unsafe.
8. Pressure control valves and stations
What they do: Regulate water pressure in different areas to prevent damage to the network.
What happens if they fail: Without power to operate automatic valves, overpressures increase when pumping resumes, causing breaks, leaks, and new service interruptions.
9. Wastewater treatment plants (EDAR)
What they do: Treat sewage before returning it to the environment.
What happens if they fail: Without treatment, liquid waste is released uncontrollably, contaminating rivers, lakes, and coasts, creating environmental crises and serious health risks.
10. Sewage pumping stations
What they do: Lift sewage in areas where gravity drainage is not possible.
What happens if they fail: Sewage stagnates or overflows in the streets, causing foul odors, disease risks, and urban infrastructure collapse.
11. SCADA control systems (telemetry and automation)
What they do: Monitor and control the entire water system in real-time through sensors, software, and telecommunications.
What happens if they fail: Operators cannot see the status of each pump, valve, or tank, becoming blind to incidents and hindering system control and recovery.
What they do: Provide backup electricity in case of a general network failure.
What happens if they fail: They operate on limited fuel (diesel). In a prolonged blackout without refueling, the generators shut down, and all critical facilities become completely inoperative.
13. Automatic chlorination systems
What they do: Dose chlorine or other disinfectants to ensure water is potable.
What happens if they fail: Lack of disinfection causes stored or in-transit water to lose its microbiological quality, increasing the risk of diseases like cholera, gastroenteritis, and hepatitis.
14. Water tanker refill points
What they do: Allow filling water tanker trucks for distribution in affected areas.
What happens if they fail: Without power to pump water at refill points, tankers cannot be supplied, severely limiting emergency supply alternatives to the population.
Recovering water: a slow and risky process
Even when the power supply is restored, and in a scenario like the one presented, the normalization of the drinking water service would not be immediate. The lack of pressure control in the network could cause water hammer effects, pipe breaks, and new leaks.