The water that moves the sun

Central reservoir of the Drinking Water Treatment Plant (DWTP) of l’Ampolla, where the water is regulated and stored before beginning its treatment.

With a simple gesture we turn on the tap — even the most tech-savvy now do it with their voice. And out comes water, the source of life. Just like when we flip a switch and the light turns on, seemingly without any effort for those of us fortunate enough to live in developed countries. We make the gesture, and the water appears, but this invisible current that gives life to everything requires a complex network that transforms it and carries it all the way to our homes.

This silent infrastructure needs energy to drive the journey of water, from its collection to the final consumer, powering water pumping stations, control centers, and the digitalization of data. A process that works like a gear system, fitting together as water purification advances. What makes it complete — and fascinating — is that another vital and clean source comes into play: the sun, providing the energy needed for everything to function.

From surface treatment to underground transport, this is how water flows through the technical heart of the Tarragona Water Consortium.

En el laboratorio de control de calidad, se analizan diariamente más de 275 parámetros. Un trabajo riguroso para garantizar que el agua cumpla todos los estándares sanitarios.

An example of this is the Tarragona Water Consortium (CAT), which captures, treats, and distributes drinking water to 70 municipalities and 27 industries across the entire province of Tarragona. Endesa built two photovoltaic solar plants for the consortium, totalling more than 8,500 panels. Through them, solar energy is harnessed to cover 10% of the energy the CAT needs to carry out its work. That is what drives the journey of water.

Every drop that supplies the regions known as Camp de Tarragona and Terres de l’Ebre is captured through the channels along the left and right margins of the Ebro River in Campredó, a small settlement located 7 km south of Tortosa. From there, it is pumped upstream and travels through large pipelines until it reaches the Drinking Water Treatment Plant (DWTP) of l’Ampolla, where an immense infrastructure awaits—one that almost resembles a lake. Only the concrete holding the water, 6 metres deep, reveals that it is not. Even birds are drawn to its stillness or stop by to drink.

This is the lungs of the system: a vast reservoir containing 175,000 tonnes of water, serving a dual purpose—regulating the purification process and acting as a strategic reserve in case of an incident, allowing the supply to be maintained for hours. In summer, 12; in winter, 24 — in other words, a full day.

Vista de los paneles solares instalados en la cubierta de laEstación de Tratamiento de Agua Potable de l’Ampolla. La energía solar cubre el 26 % de sus necesidades energéticas.

It is within this facility that water is transformed to make it suitable for consumption. From pre-ozonization to post-ozonization, passing through the various chambers, flocculators, clarifiers, sludge treatment systems, and sand or carbon filters until reaching the treated-water reservoir—an enormous building whose roof hosts more than 6,600 solar panels covering 30,800 m², equivalent to about three and a half football fields. It is the largest photovoltaic installation in operation within the water treatment sector in all of Spain. From here, the stunning Ebro Delta unfolds in the distance, where water also comes to life at the river’s mouth and its fusion with the Mediterranean.

At CAT, every drop is controlled, every second is monitored. From the control room in l’Ampolla, the brain of the facility, 50,000 signals are received, allowing operators to know what is happening at every point, every ten seconds. Pressures, circulating flows, reservoir levels, the status of motor pumps, engine temperatures… Surveillance is constant, 24 hours a day, 365 days a year.

Teams examine every detail, including in the laboratory, where more than 275 parameters are analysed each day—60,000 per year. This is where science fine-tunes purification and ensures purity, verifying that everything is in balance: removing what is unnecessary, reinforcing what matters, until the process reaches the treated-water reservoir.

Pipes through which water is transported across the more than 400 km of network that supply much of Tarragona.

The water leaves the Drinking Water Treatment Plant ready, transformed into potable water, and flows through a network of more than 400 kilometres of pipelines thanks to another pumping station, some running through natural landscapes, others through tunnels. Some pipes are so large that a person up to 1.6 metres tall could stand inside them. These hundreds of kilometres of pipelines run across much of the Tarragona coastline, from Alcanar to Cunit, and inland to Blancafort and Solivella, covering the northern part of the region.

All of this would not be possible without the 23 pumping stations that form part of the consortium and are major energy consumers. One of them, where the CAT’s central facilities are located, in Constantí, houses the second solar plant that Endesa built for the consortium, with more than 1,900 photovoltaic panels. From there, and with the ever-growing support of solar energy, water is lifted from the reservoirs to the secondary and coastal distribution lines, which eventually deliver it to reservoirs managed by municipal entities. From that point on, the local distribution network takes over and continues the journey to households.

A long and vital path, where innovation and sustainability intertwine just as water and sunlight do, in harmony. It is beautiful to see how sunlight becomes energy to move something so essential for life: water. Both silent, yet utterly indispensable.