Hadrian’s Aqueduct: A 1,863-year-old Roman solution to Athens’ water scarcity problem

The amount of 1,000,000 cubic meters per year is estimated to be the water saved for Athenians if Hadrian’s Aqueduct is utilized along its entire length. This means—although it may seem utterly inconceivable—that an ancient water project, 1,863 years old, crossing eight municipalities of Athens from Acharnes to Kolonaki and covering a distance of 24 kilometers, still has the capacity to transfer 1,000,000 cubic meters of water annually for any use other than drinking.

Thus, wherever there is a connection to Hadrian’s Aqueduct, water extraction for irrigation, cleaning, etc., will replace the consumption of drinking water from the EYDAP network. Moreover, aside from saving this precious resource—especially under drought conditions due to the climate crisis—the non-potable water of Hadrian’s Aqueduct contains nutrients beneficial for plant growth.

Conversely, potable water is wasted in irrigation as it undergoes cleaning and filtration processes that neutralize trace elements valuable to plants. Equally remarkable as the endurance of the ancient Roman aqueduct, its ingenious design, and its functionality is the fact that it participates in the natural water cycle in the environment: based on its operating principle, Hadrian’s Aqueduct “captures” water (a technical term meaning it gathers water from natural cavities, rivers, and streams encountered—or formerly encountered—along its route).

When users draw quantities for their needs, part of the water returns to the ground, ideally replenishing the underground aquifer and thus, in a way, making its way back to the aqueduct. In modern terms, this type of water cycle is referred to as “circular/green economy practices,” etc.

Pilot Supply

At present, all of this seems too good to be true. However, it is already—albeit partially—a reality, as demonstrated by the pilot reactivation of a section of the aqueduct approximately 4.5 kilometers long, passing through the lower side of Chalandri, near Kifisias Avenue.

Regarding the potential full utilization of the aqueduct’s 24-kilometer length, EYDAP has conducted the relevant study. According to this study and corresponding calculations, the benefit for the water reserves of the capital across a chain of eight neighborhoods (Acharnes, Kifisia, Metamorfosi, Iraklio, Nea Ionia, Chalandri, Neo Psychiko, Ampelokipi) would amount to about 1,000,000 cubic meters annually.

From this perspective, it will be fascinating to see how the Hadrian’s Aqueduct revitalization project will function in practice. Starting in March 2025, EYDAP will begin a trial supply of non-potable water to Chalandri residents who expressed interest and connected to the network constructed over the past few months, supplementary and parallel to the aqueduct pipeline.

Initially, the plan aimed to serve about 70 consumers. However, the overwhelming response from interested parties tripled the demand, compelling EYDAP to further enhance the supplementary infrastructure to ensure the technical smoothness of the non-potable water distribution network in Chalandri.

The Chalandri Example

Leading the revival of Hadrian’s Aqueduct, Chalandri is pioneering by utilizing an ancient monument not as a tourist attraction, as is common, but as part of a holistic, green urban development project emphasizing sustainability and community participation in every aspect—from design to promotion and historical documentation.

Centered around the reactivation of the aqueduct, various cultural activities were developed in a broad sense, ranging from water management by the local community to redevelopments around EYDAP and aqueduct works, and even organizing events, festivals, etc.

Through the Cultural HIDRANT Project and funding from the European Union, the Municipality of Chalandri has elevated the revival of Hadrian’s Aqueduct to a global model, an international case study of innovation. According to Mr. Christos Giovanopoulos, director of the Cultural HIDRANT Project, “Reintegrating Hadrian’s Aqueduct into the daily lives of Chalandri residents for their non-potable water needs is immensely significant.

Firstly, the water cycle, which previously ended in the sea without being utilized—from Parnitha to the Dexameni reservoir in Kolonaki (although in practice, Hadrian’s Aqueduct is not continuous due to damage in at least three locations)—is now restored.” Now, at least Chalandri residents and potentially future residents of the other seven aqueduct municipalities understand that they can contribute to water conservation by using non-potable water for watering trees in their gardens, cleaning spaces, etc.

Mr. Giovanopoulos also notes, “It is noteworthy that non-potable water networks exist in many cities in Europe—and beyond. In Paris, for example, non-potable water is used by the local municipality for irrigation and cleaning purposes. However, in Chalandri, for the first time worldwide, citizens themselves are given the opportunity to use it.

Indeed, Chalandri’s example has attracted interest from at least 15 cities across Europe to transfer our expertise and methodology applied to Hadrian’s Aqueduct to locations with existing older non-potable water supply infrastructure. Representatives from cities in Spain, Portugal, Serbia, Belgium, and even Italy’s capital, Rome, will visit Chalandri as part of the first Policy Workshop on managing cultural and natural resources under the European Urban Initiatives program, co-funded by the EU.”

Water distribution to Chalandri residents from Hadrian’s Aqueduct will occur in two ways: directly and indirectly. Properties close to the pipelines will connect directly to the designated waterlines. Consumers farther away will receive non-potable water from two water tankers acquired by the Municipality of Chalandri for this purpose.

The distribution will be managed by the Hadrian Chalandri Community, essentially a committee comprised of residents, in collaboration with a special-purpose cooperative, also formed by local residents, likely Roma, who will deliver water to consumers’ tanks. The unexpectedly high demand increased the network’s projected supply from 25,000 to 80,000–90,000 cubic meters annually.

Project Completion

The Hadrian’s Aqueduct revival project, specifically within Chalandri’s boundaries, has been completed by EYDAP. Technical works cost €1.2 million, while redevelopments around the aqueduct route amounted to €5.5 million.

The Vision

However, integrating the project into the appropriate EU program has its own unique history. The initial idea for the aqueduct’s reuse had been discussed for years, but credit for initiating the necessary steps is owed mainly to a Chalandri municipality official, former Deputy Mayor Kostas Gerolymatos.

In 2019, the municipality drafted a proposal to include the aqueduct reactivation project in the Cultural HIDRANT program. The Greek proposal was one of 11—out of 222—selected by the EU authority for Urban Innovative Actions, which manages resources from the European Regional Development Fund.

Although Chalandri Municipality assumed overall supervision and responsibility for the program, its proposal was co-developed with seven other partners: EYDAP, the Commonspace Workers’ Cooperative, the architectural firm Th. Papagiannis & Associates, the Mediterranean Institute for Nature and Anthropos (MedINA), the NGO “Ohi Paizoume – Urban Dig,” the Antiquities Authority of East Attica, and the Institute of Regional Development of Panteion University, with the involvement of two local associations. Collaboration also extended to 12 schools across all educational levels in the area, parent associations, etc.

The vision of the residents of Chalandri extended beyond the reuse of the Hadrianic Aqueduct, aiming to integrate it into as many aspects of daily life as possible, as well as into the contemporary urban fabric of the city. Mr. Giovanopoulos highlights: “This approach differs from the simple showcasing of the Hadrianic Aqueduct as a monument or tourist attraction meant to draw visitors to the city.

Instead, the urban renovations planned and mostly implemented—the largest ever undertaken in Chalandri, covering a total area of 21,500 square meters—aim to improve residents’ quality of life through: 1) the creation of new public green spaces, 2) the expansion of the green zone and walking paths along the Rematia stream, 3) the connection of the Syneikisimos area with the city center through a continuous pedestrian zone, and 4) the use of water and green elements to create a microclimate as a contribution to combating the greenhouse effect. Additionally, the historical highlighting of the largely hidden Hadrianic Aqueduct extends beyond its identity as an ancient monument. It is approached as a collective heritage asset through documenting its presence in the recent and older life of Chalandri and the relationship of the city’s residents with it.”

A 19-Century History

The Roman emperor Hadrian (117–138 AD) aspired to ensure the luxury of baths for the aristocrats of Athens. To this end, he commissioned the construction of an aqueduct, initiated during his reign but completed by his successor, Antoninus Pius (138–161 AD).

In terms of construction, the main artery of the Hadrianic Aqueduct is an underground tunnel carved into natural rock, with a height of approximately 1.20–1.60 meters and a width of 50 centimeters. The project was executed by digging 465 shafts along the aqueduct’s route, each with a maximum diameter of 1.40 meters and depths ranging from 10 to 42 meters. The aqueduct’s main axis began at the so-called “inclined gallery” in the area of today’s Olympic Village in the Municipality of Acharnes and ended at the Reservoir, located at the eponymous square in Kolonaki.

The aqueduct’s route was designed to follow the gentlest path in terms of elevation changes. It operated primarily by naturally tapping into the groundwater layers of the earth and secondarily by transporting water from specific springs located at the foothills of Mount Parnitha. The aqueduct was further supplemented by several adjacent streams along its course.

After its construction, it remained functional for several centuries before being abandoned. It was reactivated in 1847 following the establishment of the independent Greek state and the relocation of the capital to Athens, to address the city’s acute water supply problem. Subsequently, between 1870 and 1931, successive cleaning and repair works were carried out, mainly on its final section, including the installation of metal pipes.

The Hadrianic Aqueduct served as Athens’ main water supply source until 1931, when the Marathon Dam was completed. However, it remained in auxiliary use until the mid-1970s. After falling into disuse once more, major infrastructure projects for the Athens Olympic Stadium, the metro, and other developments caused significant damage to the aqueduct. Nevertheless, as recent efforts show, the damage was not irreparable.

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