BEIJING, May 7 (Xinhua) -- The main part of the underwater museum for the Baiheliang, the world's oldest water survey device which will be submerged once the Three Gorges reservoir is filled, has been completed.

Baiheliang, the 1.6 km-long massive reef important for observing water level changes, has been covered by an elliptical transparent shield so visitors in the future can still see it.

The whole construction project of the underwater museum, the first of its kind in China, is expected to be finished by June, 2007, according to the Institute of Rock and Soil Mechanics under the Chinese Academy of Sciences (CAS), the organization in charge of the project.

Located at the upper reaches of the Yangtze River, Baiheliang only emerges from the water during the dry season. Therefore, it was a very important marker for ancestors to observe the changes of the water level and by it, they could predict if they could have a good harvest.

On the massive reef, there are more than 20 fish sculptures, serving as water-level markers. Meanwhile, about 30,000 characters of Chinese poems are also left on the stone, which were carved by Chinese poets of different dynasties.

The stone inscriptions on Baiheliang recorded about 1,200 consecutive years of the river's water levels during the dry seasons as well as its low water periods.

However, similar water survey devices in other rivers of the world only included the local water level information of less than 100 years. In comparison, the stone inscriptions on Baiheliang are much more detailed than those discovered at the Nile River.

Therefore, Baiheliang has gained fame as "a miracle in world water survey history". Engineers also consulted the water level information on Baiheliang when designing the world's largest water engineering project, the Three Gorges Project.

Since 1994, China's cultural relics protection departments have started to research how to protect Baiheliang. Experts once raised several solutions, such as building an underwater museum, or reproducing it and laying it on the bank but submerging the original one.

Finally, the solution raised by Ge Xiurun, an academician of CAS, was accepted. He suggested the covering of the Baiheliang reef by a water pressure-free container with an arch shape. Fresh water will be instilled into the container, making its inside and outside water pressure balanced. Enditem