MARÍA GÓMEZ BRAVO | Tungsteno

In the Nile Delta, many ancient Egyptian cities disappeared centuries ago beneath layers of sediment, farmland and modern development. From ground level, they are almost impossible to identify. Seen from space, however, some leave faint traces in the form of geometric lines, tonal variations or slight differences in soil moisture. Sarah Parcak, an Egyptologist and professor at the University of Alabama at Birmingham, has turned these subtle signals into a tool for locating potential archaeological sites without the need for prior excavation.

In the early 2010s, she participated in a number of projects focusing on ancient Egyptian settlements. In the Nile Delta, the contrast between cultivated land and desert areas makes it easier to detect small changes in the terrain that are invisible to the naked eye. Satellite imagery revealed geometric lines and subtle surface variations that corresponded to buried ancient structures. These were not visible ruins or cities emerging from the sand, but rather physical traces that the landscape had preserved for centuries.

Parcak began working with this type of imagery during her doctoral research at the University of Cambridge. Unlike conventional photographs, multispectral images capture information that the human eye cannot perceive. Her aim was to locate tells—mounds formed by successive layers of human occupation—and possible buried structures across the Middle East based on these minute alterations detected through infrared sensors. “To try to map the past, I have to look at it in a different way,” Parcak has said, summarising a central idea that runs through her research: landscapes preserve physical evidence of the people who inhabited them centuries ago.

Sarah Parcak explains how space archaeology uses satellite imagery to locate traces of ancient civilisations hidden beneath the ground. Credit: TED.

A new way of interpreting the landscape

The use of aerial imagery to study the terrain was not entirely new. After the First World War, photographs taken from military aircraft began to reveal ancient shapes and structures that were difficult to identify from the ground. Decades later, satellites from NASA’s Landsat programme made it possible to extend this observation to vast swathes of the planet and analyse how landscapes changed over time. But the real breakthrough lies not in conventional photography, but in understanding how buried structures affect soil, vegetation and temperature.

For example, a buried wall can alter the moisture content of the soil above it. Similarly, an adobe structure can change soil compaction and affect vegetation growth. Some constructions also generate temperature differences that become detectable at specific times of day. By analysing these subtle variations, researchers can identify areas with archaeological potential, which must then be investigated on the ground. Parcak herself insists that these tools do not replace excavation, but rather help to guide and focus archaeological fieldwork.

From isolated sites to landscape-scale analysis

The ability to analyse entire regions rather than just specific sites is one of the main contributions of this methodology. One of the best-known examples is the work carried out at Tanis, an ancient Egyptian city located in the northeastern Nile Delta. Although the site had been known for decades, satellite imagery helped researchers reconstruct parts of its buried urban layout, revealing streets, structures and occupation zones hidden beneath sediment and modern agricultural land.

The value of this type of research lies in understanding how ancient urban and agricultural landscapes were organised on a large scale. Parcak applied this same approach to the study of the funerary complexes and tombs of El-Lisht, one of the principal centres of Egypt’s Middle Kingdom, as well as to Petra in Jordan. There, she identified a monumental structure that had gone unnoticed despite Petra being one of the most intensively studied archaeological sites in the world.

This shift in perspective has influenced other projects around the world. In Guatemala, the Pacunam LiDAR Initiative, involving the Polytechnic University of Valencia in Spain and Tulane University in the US, identified thousands of Maya structures concealed beneath the dense jungle canopy, including elevated roadways and agricultural terraces.

In Cambodia, a combination of satellite imagery, radar, and large-scale LiDAR surveys confirmed the existence of an extensive urban network beneath the forests surrounding Angkor Wat. In the United Kingdom, the Stonehenge Hidden Landscapes project used ground-penetrating radar and remote sensing to detect prehistoric monuments buried around the megalithic complex.

In each of these cases, archaeology has moved beyond the study of isolated monuments to examine entire landscapes and the relationships between settlements, infrastructure, and the natural environment.

Six Sacyr professionals participated in an international volunteer program organized by the Sacyr Foundation in collaboration with the NGO UPlanet.

Paco Molina, Iván Roselló, Camila Quintín, Eva Abad, Lucía Cecilia, and Ana Grande spent a week in Bir Moghrein, an isolated village in northern Mauritania. The expedition also included Rubén Fernández, Ana Grande's son, along with a group of 30 healthcare professionals from HumanCoop, four members of UPlanet, and a professional from Viamed, Rodrigo Morilla, a former Sacyr colleague.

This marks the second edition of the volunteer program in Mauritania, which aims for Sacyr professionals to help repair and develop infrastructure that impacts the lives of the local population.

Among the projects they collaborated on, a highlight was the repair of deficiencies in the village's desalination plant to improve water production and quality. Additionally, the necessary technical documentation was created for the installation of a new containerized desalination plant, which is scheduled to arrive in the summer.

The electrical system of the health center was also renovated, a project to install new latrines in the primary school was developed, and progress was made on a one-hectare garden project to provide food for the population and create employment for women.

Finally, an entrepreneurship workshop was organized to boost the local economy among women.

A tough but rewarding experience

"On a personal level, it has been an incredible experience; it grounds you and gives you a lot of perspective on life. Professionally, it has been rewarding to be able to make my small contribution through this wonderful profession," explains Camila Quintín (Sacyr Engineering and Infrastructure).

Paco Molina and Iván Roselló, both from Sacyr Water, collaborated on improving the desalination plant's facilities. They adjusted water quality by implementing a mixing system with filtered water to extend the life of the membranes. They also created a bypass for the filter backwash water.

Paco Molina states that it is a trip "worth repeating." "It has been a tough yet kind, disheartening yet enriching, selfish yet selfless experience – a mix of contrasting feelings, but always with a positive balance," he adds.

"We have bridged gaps through effort and collaboration," affirms Iván Roselló.

"Our group created a balanced ecosystem in a remote and inhospitable place. A reality check that puts my concept of 'life' into perspective," says Eva Abad (Sacyr Proyecta).

Ana Grande (Sacyr Holding) emphasizes that this volunteering experience is a "challenge overcome." "I applied engineering outside of my comfort zone, engaged in teamwork, and gained real learning. It has been an experience that adds value professionally and personally, thanks to the people with whom I shared this adventure," remarks Ana.

"It has been a tough but very rewarding experience at the same time. Helping these people who have so little gives you another perspective on life and what is truly important, which is helping each other. I value the human warmth of my colleagues," explains Lucía Cecilia (Sacyr Holding).

Rubén Fernández, in charge of the electrical tasks, stated that "the lack of technical materials made work difficult at the clinic, but with effort and improvisation, we managed to get our job done." He adds, "It has been a different and tough experience, but I have learned so much about how fortunate we are to live in a country like ours and the ease we have in Europe of drinking tap water and finding whatever you need in any store."

Collaboration with UPlanet

The collaboration between the Sacyr Foundation and UPlanet is fundamental for integrating infrastructure in this underdeveloped region, isolated by a vast desert expanse. UPlanet, in turn, collaborates with HumanCoop, which organizes medical-surgical missions to the country, thereby creating synergies in organizing all logistics.

The next initiative we will collaborate on will be the installation of a new portable containerized desalination plant, which will arrive in Bir Moghrein in the summer.

"Our collaboration with UPlanet helps us reach these remote areas, where, thanks to our help, they can count on experts in infrastructure and water who collaborate to improve the facilities of these communities," explains Pedro Alonso, Director of the Sacyr Foundation.

"International volunteer programs help our professionals step outside their usual scope of work and grow as individuals," he explains.

"At UPlanet, we believe that community development hinges on improving basic infrastructure, which allows for laying the foundations of sustainable development. Thanks to the collaboration and contribution of the Sacyr Foundation, the actions carried out in agriculture, water, and sanitation have been a success. They have immeasurable value," explains Matías Fernández, Presidente of UPlanet, a former colleague from Sacyr Water, and coordinator of the field mission conducted in Bir Moghrein.

This project demonstrates how cross-sector innovation and collaboration can reduce emissions, optimize costs, and accelerate sustainability.

While steel production and water desalination might appear to be unrelated activities, the Sohar industrial hub has demonstrated their potential for synergy.

The Sohar 4 IWP plant, managed by Sacyr Water, requires CO₂ to stabilize the pH of the treated water, prevent scaling in distribution networks, and ensure safe water suitable for human, agricultural, and industrial applications.

Traditionally, CO₂ is sourced from external suppliers, incurring high economic and energy costs. The presence of large industrial emitters within the hub itself presented an opportunity for a more efficient solution: capturing CO₂ at its source and reusing it locally.

Industrial Symbiosis: Environmental and Economic Impact

This initiative, spearheaded by Abdullah Al Sadi, Operations Service Director at the Sohar plant, transforms an industrial emission into a key resource for water treatment. This model of industrial symbiosis reduces emissions at their source, enhances the quality of the treated water, and optimizes operating costs. 

"The use of captured CO₂ allows us to improve water quality while reducing emissions directly at their source," explains Al Sadi.

The project received Sacyr's 2025 Natural Innovators Award, in the 'We Are Excellence' category.

Operational Efficiency

The Sohar 4 IWP plant produces approximately 250,000 m³ of water daily. It currently consumes around seven tons of CO₂ per day, with projections to reach 12 tons in the coming years.

Local CO₂ capture virtually eliminates logistics costs and reduces CO₂ costs by approximately 40%.

Reduced Carbon Footprint and Chemical Usage

While the process does not reduce the energy required for desalination, it significantly lowers the carbon footprint of the treated water by substituting externally sourced fossil-based CO₂ with CO₂ captured from local industry.

Furthermore, the use of captured CO₂ reduces the need for other chemicals like hydrated lime, carbonate, or sodium bicarbonate, and optimizes chlorine usage. These benefits collectively lead to a lower environmental impact, reduced operating costs, and more efficient water chemistry.

This approach also provides access to regulatory advantages, fosters greater social acceptance, and strengthens our competitive position in markets with increasing demands for sustainability.

Looking to the Future

After two years of development, the project is now entering a new stage focused on consolidating pilots, obtaining permits, and scaling up to commercial solutions that can be replicated in other industrial environments.

This is another example of how innovation and cross-sector collaboration can transform significant environmental challenges into shared opportunities.

The 2021 eruption of the Tajogaite volcano in La Palma (Canary Islands) buried the LP-2 road while it was undergoing construction. We are currently rebuilding the section between kilometers 40 and 43, contending with the high temperatures that still persist within the lava field.

“Constructing this new road across the lava field necessitates a thorough assessment of the ground's thermal conditions, as volcanic lava flows can retain high temperatures for many years,” explains Juan Antonio Romero, Head of Topography at Sacyr Engineering in La Palma.

We have addressed this challenge by deploying drones equipped with infrared thermographic cameras for the capture, analysis, and thermal modeling of the affected terrain.

 

This technology enables us to identify areas with significant thermal activity, evaluate the technical feasibility of the proposed route, and provide recommendations to ensure safe operations for our professionals and partners.

Furthermore, this detailed analysis helps anticipate potential impacts on the road pavement structure and bituminous mixtures, as thermal variations can alter their cohesion, stiffness, and durability. This, in turn, informs the design and construction decisions for the future pavement.

This project is spearheaded by the Canary Islands Ministry of Public Works, which awarded the contract to the JV TAJUYA joint venture (comprising Sacyr Engineering and Infrastructure, Traysesa, Herquipalma, and Los Volcanes). The project is slated for completion in 2028.
 

Thermal Radiation Measurement

Infrared thermography is a remote sensing technique that detects thermal radiation emitted by objects based on their surface temperature. In the geotechnical field, this tool has proven to be an effective method for:

•    Identifying areas of residual volcanic activity.
•    Detecting active fractures and gas emissions.
•    Analyzing cooling processes in lava flows.
•    Evaluating the thermal stability of ground for civil engineering projects.

“Through the acquisition and processing of infrared images, we have generated georeferenced heat maps and graphs that illustrate the thermal evolution. The DJI MATRICE 350 RTK drone, equipped with a camera, can detect temperatures ranging from 0 to 550 degrees Celsius,” explains Juan Antonio Romero.

“This undertaking combines advanced technologies in remote sensing, thermal photogrammetry, and geospatial analysis. As a result, we enhance the road's quality and, crucially, improve site safety and occupational health,” he concludes.