Fluid fidelity
The White Crane Ridge in the Yangtze River, believed to be the world’s most ancient hydrographic survey station, is now a unique subaquatic museum, Tan Yingzi reports.
In Fuling, in Southwest China’s Chongqing, Baiheliang Underwater Museum, the first of its kind in the world, shows how the Chinese made use of water resources.
About 1,300 years ago, the ancient Chinese would gather at Baiheliang, or the White Crane Ridge, in the upper reaches of the Yangtze River when it protruded from the water during the dry season, usually from December until March.
Then they picnicked, flew kites and played games on this 1,600-meter-long natural ridge which averages 15 meters in width.
This place got its name because white cranes would flock to the place. But local people also believed that a Taoist, who meditated on the ridge and finally became immortal, transformed into a crane and flew away.
The regular exposure of the stone ridge also provided the ancient people with the chance to observe and record water levels.
So, on the huge rock there are 18 sculptures of fish that serve as water-level markers and record 1,200 years of changes in the Yangtze’s water levels.
There are also more than 30,000 Chinese characters carved into the rock there, and the area is listed as one of four State-level national treasures in the Yangtze River’s Three Gorges area.
The ridge is believed to be the world’s most ancient hydrographic survey station.
Due to the Three Gorges Dam project, the huge rock was submerged in 2001. So, a special museum was built to preserve its history.
Valuable relics
There is a long history of human hydrographic observation dating back to ancient times. And the records are found in the Nile River basin, the Euphrates River valley and China’s Yellow River basin.
Yet the stone fish water gauge on White Crane Ridge is a key development in the world’s ancient hydrographic observation. It shows the lowwater mark as a fish’s eye, and equates to a zero-water level in the river’s upper reaches.
There is a local saying that if the stone fish can be seen in winter, the coming year will provide an abundant harvest.
The fish carving is more than 1,100 years older than the Jianghanguang gauge created in 1856 in Wuhan, the capital of Hubei province, in the middle reaches of the Yangtze River.
There are a total of 165 inscriptions, 108 of which record the water levels in 72 low-water years from 763 AD in the Tang Dynasty (618-907) up to 1963.
The inscriptions show the hydrographic variations in the upper and middle reaches of the Yangtze River during the years of drought.
“These records are the most authentic and reliable ancient hydrographic data,” says Huang Dejian, the deputy director of the White Crane Ridge Underwater Museum.
The data provides scientifically valuable information about water transportation in the Yangtze River and water conservancy projects, especially for the Gezhouba Dam, the first one on the river built in 1971 and the later Three Gorges Dam, he adds.
In addition to its scientific value, the ridge inscriptions showcase a collection of works by generations of exceptional calligraphers and authors.
When the ridge was exposed in the past, many would write or inscribe poems on the rocks.
About 700 visitors have left their names and more than 300 literati etched over 30,000 characters in eight calligraphic forms there. The most celebrated work was carved by Song Dynasty (9601279) scholar Huang Tingjian.
Innovative preservation
In August 1988, the White Crane Ridge Inscriptions were made a key national cultural relic. But soon its existence faced a critical challenge.
In 1992, the country decided to build the Three Gorges Dam on the Yangtze River, the world’s largest hydropower project. And according to the plan, normal water levels would be raised to 175 meters above sea level, which meant that the White Crane Ridge would be submerged under more than 30 meters of water.
China then immediately launched a massive operation to save the area’s cultural relics before they were lost due to the rising waters.
The measures for the protection of the White Crane Ridge were both unique and technically demanding.
“We spent 10 years finding out the best way to preserve this rock.” says Huang.
“And we are still working on new technology to protect the relics.”
Chinese experts proposed seven protection schemes before the “Pressure-free Container” plan devised by Ge Xiurun was adopted in February 2001.
Ge, an academician with the Chinese Academy of Engineering and a professor at the Shanghai Jiao Tong University, worked out a plan for a museum based on the pressure-free container principle.
Under his plan, the stone ridge is enclosed in an archshaped glass covering, filled with purified water.
This ensures that the pressure on both sides of the arch is the same.
Meanwhile, two underwater corridors with long escalators from the riverbank allow visitors to descend and view the stone carvings and inscriptions through glass windows.
“There is no precedent for this,” says Ge.
“We had to rely on ourselves to find the solutions.”
The arch is made of special kind of steel which offers protection from ships weighing up to 4,000 tons.
In order to protect the inscriptions from erosion, experts from the Institute of Archaeology of the Chinese Academy of Social Sciences used resilient ethyl silicate to reinforce the carved stone.
It took seven years — from 2003 to 2009 — to build the underwater museum at a total cost of 210 million yuan ($30.88 million).
There are a total of 3,800 tons of water in the container. And the museum has 23 viewing windows allowing around 40 visitors to view the ridge at the same time. It also has 28 underwater cameras, enabling visitors to zoom in and out using touch-screens.
Visitors are also allowed to dive into the container to explore the works up close.
Over the past decade, the museum has worked with Chinese universities and tech companies to develop new technologies to protect the cultural relics.
“Our water recycling system and deep-water lighting system have greatly improved the preservation of the relics,” Huang said.
In the early days, the museum had to shut down periodically due to the deteriorating water quality in the container and a massive growth of algae on the rock. But now the water recycling system can balance the pressure in the container and purify the water.
Also, the system collects data about the river water level and flow speed in order to reduce the impact of the water pressure on the ridge.
“We inject 20 tons of purified water into the container every hour,” says Huang. “It is a huge amount of work.”
In addition, divers go into the container to clean the rock every month.
The container is equipped with a deep-water lighting system which improves the presentation of the inscriptions and reduces the power consumption.
“Most importantly, it reduces the light intensity and prevents the growth of algae on the rock,” he adds.
Also, to offer visitors a clear view of the ridge, the museum recently changed the type of glass used in the windows, replacing them with materials developed for the aviation industry.
We need to ... ensure more people are aware of the significance of these inscriptions.”
Huang Dejian, deputy director of the Baiheliang Underwater Museum
Heritage list application
In 2006 and 2012, the White Crane Ridge inscriptions were added to the provisional list of World Cultural Heritage sites that China submitted to the UNESCO.
And in recent years, Chongqing has begun to enhance its efforts to get the site formally recognized by UNESCO.
To this end, the local government has invested nearly 80 million yuan to upgrade the museum’s exhibition hall, surrounding areas and its facilities.
If its UNESCO bid is successful, the museum will become Chongqing’s second World Cultural Heritage site, after the Dazu Grottoes that were listed in 1999.
“We need to do more research on the project and increase our communication with the international community to ensure more people are aware of the significance of these inscriptions,” Huang said.
Since its opening in 2009, the museum has received about 1.5 million visitors from home and abroad.
The museum has held two international symposiums since 2009 and collaborated with the School of Archaeology and Museology of Peking University to conduct the research on the White Crane Ridge inscriptions.
Speaking about the site, Yu Xintao, a visitor from Chongqing, says: “This museum is a hidden gem of Chongqing, or even for China.
“I spent hours there, amazed by the wisdom of our ancestors and the brilliant design of the museum.”