源起：西咸城市化压力下的母亲河 | Background: the mother river under pressure
西汉文学家司马相如在著名的辞赋《上林赋》中写道：”荡荡乎八川分流，相背而异态”，描写了汉代长安上林苑的巨丽之美，自此有了”八水绕长安”的记叙。 八水之一的渭河是黄河的最大支流，也是西安和咸阳的母亲河。在西咸一体化城市扩展的背景下，渭河沿线的自然乡野河滩承受着被城市化的压力。城乡交错区的水环境不断恶化，乡野河滩迅速消失，河滩湿地被水泥护堤取代，人们对乡野大地的归属感越来越强烈。 渭柳湿地公园建设在渭河流经咸阳市渭城区河段存留不多的自然洪泛滩地之上，总长约3200m，宽约470m，占地面积约125hm2。本项目获得2018艾景国际园林景观规划设计奖唯一的卓越景观设计奖。
Wei River is not only one of the famous “Eight Rivers of Chang’an” described in Chinese historical literature and the biggest tributary of the Yellow River, but also the “mother river” of both Xi’an and Xianyang City. But as the urbanization progress of these two cities, the once natural riparian areas of Wei River have gradually been replaced by concrete dykes and decorative greenery planting. The constant degradation of the wild riverside landscape has also contributed to the loss of the sense of belonging, for the people who have lived in this rural area for generations.Weiliu Wetland Park was constructed on a section of Wei River’s riparian zone outside of Xianyang City, which was one of the few naturally flooded river sections that remained. It is approximately 3200m long and 470m wide, with a total area of 125ha.
▼项目地区位及上、下游现状，Images above: site location, existing conditions upstream and downstream
胁迫与问题：环境恶化、生态退化和消失的乡野生活 | Issues: water pollution, ecological degradation and the gradual loss of rural landscape
The project site had several major issues: The flood plain of the Wei river immediate upstream had been replaced by engineered concrete dykes, which put more flood pressure on the site. The adjacent area downstream had also been urbanized but with decorative planting, causing a major loss of local habitat and biodiversity. There were several roughly dug ditches across the site carrying stormwater run-off (and sometimes leaked sewage) from the city to the river, which has polluted not only the river itself but also the riparian aquatic environment (local sampling showed riparian water quality worse than Class V of the National Surface Water Standards). Finally, local residents had reclaimed a large area of the site for lotus ponds and vegetable farming, which showed a demand for the lost rural lifestyle.
site before – existing earthen dyke, deserted riparian area, stormwater ditch and reclaimed vegetable farms
总体思路：构建综合服务的绿色基础设施 | Overall Strategy: Creating integrated Green Infrastructure
To solve the issues described above, the comprehensive restoration and reconstruction of the local riparian ecosystem was the main goal for the project. A plan was developed to create urban Green Infrastructure through a series of strategies including adaptive flood control, stormwater management, water quality improvement, waste water reuse and biodiversity restoration, which would transform the site into an urban park that provides multiple values on environment and people.
▼总平面图，the master plan
▼鸟瞰效果图，bird-eye view impression
▼恢复后的自然河滩湿地，reconstructed natural riparian wetland
弹性景观设计，适应洪水过程 | Creating resilient, flood adaptive landscape
Frequent urban flooding due to climate change has become a global issue in recent years and Wei River has also suffered from increasing pressure from flooding, which is the project’s first priority. In order to restore the resilience of flood retention and utilize riparian spaces, an adaptive landscape was created based on the existing topography: the lowest areas were designed to be floodable natural wetlands, areas of lower flood risk were used for constructed wetlands and the highest areas on site were designated for recreational and leisure spaces. Bioengineering techniques were used on all flood control dykes inside the park except the outer dyke along the northern boundary (designed for one in a hundred year flood event). Techniques such as willow mattress revetment, riprap, gabions, and grassed slope were used for flood protection, biodiversity restoration and habitat protection.
▼5年一遇区域生态驳岸，grassed dykes for one in five-year flood protection
▼20年一遇生态护岸，riprap dykes for one in twenty-year flood protection
the outside dyke and associated level change was utilized to create tiered gathering and leisure spaces
利用原有土堤，构建渭柳绿廊 | Reusing the original dyke for green corridor
The main spine of the park was a green corridor that moved through the center of the park. It was built upon an existing earthen dyke flanked by willow trees. The trees were all retained and quickly became a unique scenic feature of the new park.
▼渭柳绿廊在现状土堤基础上改造而成，change existing earthen dyke into the central green corridor
▼树荫下的休闲廊道是贯穿公园东西的中轴线，retained existing trees flanking the central corridor make a unique scenic feature of the new park
污水净化，废水再生 | Purifying waste water for reusing
In order to remove water pollutants and reuse waste water at the same time, a buffer belt of constructed wetlands was created between the city and the river. All polluted water from the drainage channels that ran through the site was firstly collected into WWTP. The constructed wetlands were designed for treating outlet water from a WWTP, and producing recycle water that meet Class III-IV standards using for landscape irrigation, the aquatic playground and finally directed to replenish the natural riparian wetlands. The design of the constructed wetlands was based on the post-treatment water quality targets of Class IV standards and used subsurface wetlands primarily with supplementary surface wetlands. Oxidation lagoons were also added to the process for flood buffering, reoxygenation and water distribution.
▼水资源净化及综合利用总体方案，a comprehensive water management plan
▼湿地组合提供了环境教育和休闲体验的机会，constructed wetlands also provide opportunities for environmental education and experiences
协助自然恢复力量 | Assisting natural recovery process
The key for a successful habitat restoration is utilizing nature’s own regenerative power. After removing most of on-going human disturbances such as rubbish dumping and sand dredging, the project set its goal on recreating a diverse local habitat. Using existing trees and wild reed ponds as a foundation, the design applied minor earth shaping and careful replanting of local trees, shrubs and aquatic plants to restore shelters and habitats for aquatic life, amphibians and birds.
▼自然的力量——栖息地的恢复，the power of nature’s own ability to recover
▼通过微地形调整重塑河滩生态湿地，recreating natural riparian wetlands by minor earth shaping
▼栖息地的恢复带来了鸟类的回归，return of local birds after habitat reconstruction
回归乡野，体验自然 | Returning of rural life and natural experiences
In order to satisfy local demands for rural and natural activities, leisure areas such as civil squares, aquatic playgrounds, urban farms and rustic fitness zones were included in the park with a touch of local cultural elements. Using water as the main theme, the design gave nearby residents and park visitors plenty of opportunities to return and experience the restored natural riparian area.
▼孩子们在湿地亲水区玩耍，children were having fun in the aquatic playground
▼湿地是孩子们探索自然的最佳场所，wetlands were the best places for exploring nature
▼湿地亲水区每天吸引着众多市民前往休闲体验，many visitors were attracted by the wetlands everyday
▼跌水堰既能满足复氧功能又为湿地增加了许多体验乐趣，small dams re-oxygenates water for the wetland and at the same time became a play feature
▼秦腔文化广场为市民提供了理想的集散、休闲和活动场所， were larger spaces designed for gathering and resting within the park
艺术化的生态设计 | Creating artistic experience in nature
One of the artistic elements was expressed through two colorful bridges in the wetland area. The two intertwining structures raised and lowered through the landscape, forming boardwalks, bridges and viewing platforms, which symbolized the integration of water and the local culture.
▼夜间的景观桥为公园增添了一分色彩，colorful bridges at night
▼象征自然和文化的两色栈桥交相辉映，intertwining bridges symbolizes the integration of water and local culture
▼景观桥和栈道相映成趣，design details of the bridge and boardwalk
最低成本、最大效益的可持续设计 | Low cost sustainable Landscape with high benefits
Social and economic benefits were carefully considered at the very beginning of the project, which aimed at maximizing the project’s benefits while keeping the construction and maintenance costs down. After the completion of the project, a thorough evaluation process was carried out in conjunction of Beking University, in order to determine the environmental and social performances of the park and provide valuable experiences for similar projects in the future.
One year after the its completion, water quality monitoring spots across the park all reported results better than the Class III-IV standards. Comparing to water sample took from the original stormwater ditches on site before the construction of the park. The levels of COD, NH3-N, TP and TN in the water had shown a reduction of 89.6%, 98.4%, 96.6% and 79.5 respectively while the total quantity of water reused after treatment reached 2.4x106m3 per annum. Cost-benefit study showed the average construction cost for the park was RMB80 per m2, which was less than one third of similar local parks in Xianyang. As regarding the environmental benefits of the project, in addition to the improvements in water quality mentioned above, the average scores for different areas of the park on the Shannon-Widener Index (measuring local biodiversity) were improved to 1.57-1.91 for herbaceous plant community and 2.11-2.33 for trees community. The social benefits of the park were reflected in the results of a public survey: out of the 462 valid questionnaires received, the overall satisfaction rate for the new park was 94%, in which the satisfaction rates for comfort, experiences of nature, children’s recreation and leisure activities for the elderlies were 90%, 86%, 77% and 80% respectively. Lastly, nearby residents reported an increase in real-estate values of the adjacent areas after the park’s completion, though actual economic benefits of the park were less measurable at this stage.
▼项目建成后综合评估主要结果，summary of key findings from the evaluation
结语 | Conclusion
Green Infrastructure is a systematic approach for providing comprehensive eco-services with multiple benefits. The project integrated adaptive flood management, constructed wetland and habitat restoration techniques within the same space, making a floodable riparian zone, a stormwater management wetland and an urban park all into the one Weiliu Wetland Park, and in the process raised a good example for the building of ecological civilization on the background of sustainable rural-urban development process.
Weiliu Wetland Park – Restoration and revival of Wei River riparian zone
Design Firm: Yifang Ecoscape
Location: Xianyang, China
Tags: Green Infrastructure, River Restoration, Urban Park, Rural-Urban Development
Award: Best of the Best Idea-King 2018 Award