Intensive Efforts Made in Jiaxing to Build a Model City for Sponge City Construction
Since the pilot construction of the first batch of national sponge cities in April 2015, Jiaxing
has adopted such measures as reducing pollution sources, controlling process and making end treatment to gradually improve water quality and ecological environment and reshape the landscapes of "green banks, beautiful scenes and clear water abundant in fish". After three years’ efforts, local ecological environment, water quality, urban quality and people's life have been further improved. Now Jiaxing is striving to build a model sponge city in plain regions rich in rivers but scarce in clear water resources.
Water quality was improved after the pilot construction of the sponge city.
“These water is drawn from Fanni Lake, then sinks into the wetland in a tiered way and at last is purified, reducing pollutants and purifying the water.” Zheng Tao, a manager of Jiaxing Project Team of Tsinghua Holding Human Settlements Environment Institute, said at a subsurface wetland near the entrance to Fanni Lake Campus of Jiaxing Experiment Junior School yesterday afternoon.
Water runs through this tiered wetland that is like a harvested rice land into an outfall in the east and finally into the Fanli Lake. A piece of equipment is fixed in this outfall to monitor the SS index of the water purified by the subsurface wetland and send the data to the detecting system, and the data analysis is then made to know this equipment’s roles in reducing pollutants.
“According to the data monitored, this sponge equipment plays an obvious role in reducing pollutants of pollution sources.” said Zheng Tao. The reporter learns that reduction ratios of SS and COD in the pilot area are both directly proportional to the control ratio of total runoff and a logarithmic growth is achieved with the annual growth of the total runoff. As requested, the target of the control ratio of the total runoff in the pilot area should be 78%. When this target reaches 80.71%, 82.41% and 83.5% of SS and COD are reduced respectively.
Compared with the past, Jiaxing has made greater progress in enhancing water environment through the pilot sponge city construction and its water quality monitored in the pilot construction area has been improved remarkably. Take local water function zones as examples, there are three ones in Jiaxing: Pinghu River, South Lake and Haiyan River. In accordance with the requirements of National Water Conservation Ministry, the water quality of the Pinghu River should be up to Grade IV and that of the South Lake and Haiyan River should be up to Grade III. The third-party monitoring company made twice-a-week collection and analysis of the sampled water from these function areas, which showed that their main assessment indexes were all up to standards and their surface water quality was identified as qualified.
Jiaxing will integrate the pilot construction of the sponge city into the construction of urban infrastructure, and fully put into practice the construction idea “sponge+” and “+sponge” to improve urban quality.
As a main entrance to urban areas of Jiaxing, Nanhu Avenue used to belong to vehicles but not to pedestrians for its two sides were poorly decorated and covered somewhere with puddles in rainy days. In the pilot construction of the sponge city, rainwater pipe networks have been constructed and its landscapes have come into being. Now it has become a model window for demonstrating urban scenery and the achievements in the pilot sponge city construction.
“We arranged well the space between sidewalks and green lands and optimized botanical ecology in green lands so that a harmonious relationship was established among roads, rivers, plants and cultures.” said an official from Jiaxing Sponge City Construction Office. Currently residents nearby like to stroll along this avenue when it is fine.
“Sponge elements” were integrated into the upgrading of 26 urban roads with a length of 50 kilometers, which improved the quality and charm of urban roads, eased traffic pressures and enhanced transport efficiency while getting rid of water logs. In addition, the room for residents’ entertainment has been further expanded and the whole city has become more livable through upgrading Jiaxing Botany, Central Park and Huancheng Road.
A series of sponge technologies were explored.
Measures were made to solve problems such as weak water seepage of mucky soil and high underground water levels by developing new products and technologies to issue locally adaptable sponge city construction measures. In this respect Jiaxing has applied for over 10 patents, made various designs and developed technological products, lots of which have been commercialized and widely applied in the pilot construction, shortening the construction period and ensuring good construction quality.
During three-year pilot construction of the sponge city, such locally adaptable technologies have been used as green roofs, rainwater gardens, seepage road surfaces, buffer zones, rainwater wetlands, filtering ditches or wells and planting grasses in shallow ditches.
For example, road surfaces made of pervious materials are expensive while local earth is sticky, which increases the maintenance cost for the construction of green lands for perivous road surfaces are easily blocked. In the pilot construction, the roads with strong water storing capability and pervious road surfaces were built.
According to an official from Jiaxing Sponge City Construction Office, Jiaxing has made outstanding achievements in the pilot sponge city construction, but short-term effect is not the target, so ecological improvement is always on the way and long-term mechanisms should be established. Based on three-year efforts in the pilot construction, this city has summarized abundant experiences, established a set of locally adaptable standards, technological systems and talent systems in terms of the sponge city construction and will be widely applied in building sponge cities.