SIEM REAP - Angkor Archaeological Park, often called a "hydraulic city," mastered the art of water management by engineering an intricate system of reservoirs and canals between Kulen Mountain and Tonle Sap Lake. This network not only sustained agriculture but also fulfilled religious needs for the sprawling ancient city of temples and villages.

The reservoirs, or baray in Khmer, were royal commissions, often featuring a temple at their center dedicated to the reigning king. Among them, the West Baray (Baray Khang Lech) stands out. Spanning roughly 8 by 2 kilometres, it is the largest man-made reservoir at Angkor, capable of holding 56 million cubic meters of water—still crucial today for Siem Reap’s agriculture and urban water supply.

At its heart lies West Mebon, one of Cambodia’s most distinctive temples, once home to the bronze Reclining Vishnu—the largest ancient bronze statue found in the country, measuring over five meters in length.

On April 18, senior journalist Ky Soklim of ThmeyThmey Digital Media interviewed Dr. Hang Peou, a Belgian-trained hydrologist and current director-general of the APSARA National Authority, which oversees Angkor’s preservation. Seated near West Mebon's eastern facade, Dr. Hang discussed the exceptional historical and cultural value of the temple and its artifacts, ahead of their upcoming exhibition at the Guimet Museum in Paris.

Ky Soklim: How did the restoration look like many years ago here at West Mebon temple?

Hang Peou: The story goes back more than a hundred years ago. In 1898, French School of Asian Studies, known in French as École Française D'extrême-Orient, was created to study Indochina as a whole [Cambodia, Laos, and Vietnam], and to study the Angkor site in particular. In 1908, Conservation D’Angkor was also created to protect and preserve the heritage of Angkor. This included major temples like Angkor Wat, Bayon, Preah Khan, and so on.

Around the 1950s and 1960s, Angkor site had become one of the largest restoration sites in the world, employing around 1,000 restorers both French and Cambodians. Back then, French researchers led the projects, while Cambodian restorers implemented the actual work on stones, an intangible heritage which had been passed down through generations. As you can see here, the eastern facade of the West Mebon temple was once restored by French researchers during the early to mid-20th century.

Although the immense size of the reservoir overshadows the temple, the temple itself, at 100 meters on all four sides, is a relatively large temple. West Mebon takes on a very unique architectural style. Although surrounded by the vast reservoir, the temple also contains within itself another reservoir inside, with a central island, and finally a well in the very middle containing water. The central island is connected to the eastern facade by a stone-earth causeway. Each facade was adorned with three highly decorated towers. Each corner also had its own tower. In total, there are 16 towers.

The key is to have a temple that acts as a religious monument, and a station where water level can be measured scientifically. With this large quantity of water, a small amount of disturbance can exponentially offset the measuring result. Therefore, to stay away from turbulence especially outside the temple, people of the past would take measurements inside the central well where water was calm and more accurate.

At the central island, the revered bronze statue of Reclining Vishnu, was held on a pedestal next to a statue of a Shiva Lingam. The lingam, instead of being a solid stone all the way across, was actually hollow on the inside. This allowed water to be channelled in and out.

Upon observations on the different elevations of the temple structure, we believe that when the water rises, the surface would touch the Reclining Vishnu statue, making this revered deity seemingly float on a mythical ocean. Zhou Daguan, a Chinese diplomat who visited the Angkor site in the 13th century, also mentioned the West Mebon temple, and the Reclining Vishnu.

Ky Soklim: How badly had the West Mebon temple deteriorated?

Hang Peou: The West Mebon temple was one of the most deteriorated temples in Angkor Park due to a number of factors such as the lack of proper maintenance, strong wind, rains, reservoir waves, and more. Again, it is literally in the middle of a very large reservoir. With photographic evidence taken by French researchers in the early days, most of the temple’s upper section including its towers had fallen. Yet, the foundation underneath remained strong.

Some stone blocks from West Mebon were found as far away as the reservoir's embankment. It is believed that people in the past, considering the stones sacred, might have dragged them there as an act of devotion.

The temple has been revered across generations. Before restoration efforts began, religious offerings were often seen on the central island. Even today, many visitors come to West Mebon to carry out religious activities.

Between the initial restoration efforts of the 1940s and 2012, no major restoration took place—only routine maintenance by the APSARA National Authority.

After completing the restoration of Baphuon temple, the French School of Asian Studies (EFEO) took on the challenge of restoring West Mebon. Work officially began in 2012 and was originally expected to finish by 2016. However, the restoration proved more complicated than anticipated, largely due to the difficulty of locating scattered stones and understanding how they fit together. Since then, Cambodian and French teams have worked side by side, overcoming technical hurdles. Cambodian conservationists, sculptors, engineers, and architects have all contributed to the effort.

To ensure restoration could continue year-round despite monsoon rains, a cofferdam was built around the temple, keeping the inner area dry. Stone materials and heavy equipment had to be transported by boat, as the soft soil made trucks unusable. Detailed 3D models were extensively tested before actual restoration work began.

The project is now slated for completion by October 2026, in time for the Francophonie Summit—the first to be held in Cambodia, welcoming French-speaking countries from around the world. Once finished, the site will reopen to the public, with special displays showcasing artefacts that could not be fully restored, offering visitors a chance to learn more about the temple’s history.

Ky Soklim: How about the bronze statue of Reclining Vishnu?

Hang Peou: In 1936, French researchers (Henri Marchal and Maurice Glaize) discovered the statue at West Mebon, buried underground and broken into many pieces. It was first restored in Cambodia and later housed at the National Museum of Cambodia in Phnom Penh. In 2024, the statue was sent to France for further study, restoration, and exhibition at the Guimet Museum, alongside other ancient Asian artworks. It is also scheduled to be displayed in the United States afterward.

Normally, the Cambodian government is reluctant to lend this statue abroad, as it is the only one of its kind. However, sending it to France offers a valuable opportunity, as French experts are contributing to its restoration.

Ky Soklim: Can the statue be returned to its original location at West Mebon temple?

Hang Peou: It is very hard to say for now. We have to understand that the statue is very old, and fragile. Putting it back in the middle of a reservoir makes the statue hard to protect. How about a replica? Or glass panels which have illustrations that project virtual images of the statue? With all these possibilities, we have to stick to the rulebook, the Angkor Charter. We have to deeply consider the matter before creating something new out of the original.

Ky Soklim: Which one came first? The reservoir or the temple?

Hang Peou: Perhaps, they were both being constructed at the same time. For example:

Indratataka, a dried reservoir to the southeast, was constructed before the Lolei temple in the middle of the reservoir during the reign of King Indravarman I.

Yasodharatataka, a dried reservoir to the east, was created at the same time with the East Mebon temple in the middle by King Yasovarman I.

Jayatataka, a wetted reservoir to the north, was also created at the same time with the Neak Poan temple in the middle by King Jayavarman VII.

Yet, the west reservoir has no official name like the three reservoirs mentioned above. Since it is so large, it may have been constructed by two reigns of kings. It is believed that the reservoir was commissioned first by King Suryavarman I and completed by King Udayatiyavarman II. Conflicting inscriptions also make things harder to be sure.

Upon excavation at one of the embankments in 2010, studies revealed that the west reservoir took somewhere around 50 years to complete. In addition, why does “embankment” seem to be the key word here? This is because the west reservoir was not dug up. Instead, embankments of earth were raised to contain the water flowing from the mountains and other tributaries.

Why do we know this? In 2005, just 500 meters from the West Mebon temple, a prehistoric burial site called Koh Ta Meas was discovered when the water was low. Considered to be around 3,000 years old, the site was only 25 centimetres below the bottom of the reservoir. (Replicas and information on this burial site are highlighted permanently at the Preah Norodom Sihanouk-Angkor Museum in Siem Reap city).

Plus, right at the southern embankment of the reservoir, Ak Yum temple, a pre-Angkorian monument, was buried inside the embankment itself. The temple was a landmark of a former city during the 7th century. So, you see, the reservoir did not just pop out from nowhere. The site has been settled by humans for many thousands of years.

Conducted in Khmer for ThmeyThmey Digital Media, the interview was translated by Ky Chamna for Cambodianess.