The antique technology dating back to China?s Ming and Qing dynasties can be found in the Circular Wall (Tuancheng) of Beihai Park, a superbly well preserved imperial garden in Beijing, is to be widely used in the capital?s urban greenery construction, according to sources from the municipal park authority. Adoption of this antique technology is expected to promote efficient rainwater collection and the irrigation of grassland.

The 4,500-square-meter Circular Wall in the park is actually a round terrace with rich vegetation. Groundwater from the terrace for fostering vegetation is far from enough. However, gardening experts have found that all the antique trees and other plants in the Circular Wall are growing quite well.

To explain the situation, the Beihai and Jingshan parks under the administration of Beijing Municipal Bureau of Parks launched a two-year research project on the antique rainwater technology used in the Circular Wall. Experts discovered an underground circular drainage system in the terrace where at each turning point there was a pit to collect rainwater and create a backflow. Via this way, underground water was collected and reserved and used to irrigate the trees. History of these collecting pits dates back to the Ming and Qing dynasties almost 600 years ago.

The irrigation work of grassland around the Second-Ring Road of Beijing has been set to use this irrigation technology.

Seventy percent of the ground area of Beijing is occupied by construction, roads and waterproof areas, leaving less than 30 percent of soil for grassland. However, urban grassland plays an important role in conserving groundwater resources, reducing surface water runoff and supplementing the amount of urban underground water.

Beside Beihai and Jingshan parks, Longevity Hill (Wanshoushan) in the Summer Palace and Beijing Botanical Garden has also taken measures to collect rainwater for irrigation.

(China.org.cn by Zhang Tingting April 5, 2003)