Across the globe, single-objective flood control infrastructure has turned rivers into concrete channels, stripping them of ecological resilience and aesthetic value. At the same time, 85% of wastewater is discharged untreated, polluting rivers and oceans. While primary treatment is relatively affordable—removing odour, heavy metals, and pathogens—deep treatment to eliminate nutrients such as nitrogen (TN) and phosphorus (TP) is both energy-intensive and costly, especially for developing countries. Ironically, these nutrients are valuable as fertilisers but are treated as pollutants in urban systems. Liyumen Park presents a nature-based, symbiotic solution that rethinks this paradigm—by turning a problem into a resource and combining ecological regeneration with infrastructure transformation.

Drawing from previous pilot studies, 10km² of constructed wetland can purify 0.8km³ of primary treated wastewater from Grade V (polluted) to Grade III (eco-friendly), without relying on energy-intensive tertiary treatment. This transition would otherwise require 250% more energy and double the cost. The Liyumen Waterway integrates 56km² of living walls and wetland zones—capable of treating 5.1km³ of effluent per day. When fully implemented across the 280km² Blue Circle masterplan, up to 25.5km³ of Grade V water could be restored annually—equivalent to 12% of the city’s total treated wastewater—saving 70% in energy consumption, or roughly 2% of the total energy use of Shenzhen’s urban district.

As Shenzhen’s new central business district, Qianhai spans 15km² and is planned to host more than 700,000 daily users. With urban density reaching its limit, the demand for accessible green space is critical. By converting grey infrastructure into a green-blue network, Liyumen Park offers a network of lush, shaded spaces adjacent to office towers. These ecological corridors not only improve thermal comfort but also enrich the daily lives of workers and residents—encouraging outdoor dining, walking, and recreation. The design reintroduces nature into a dense, tropical city of concrete and steel, mitigating microclimate extremes and transforming lifeless infrastructure into vibrant public space.

The combined strategies of vegetation, water treatment, and material reuse result in significant carbon savings:

• Cooling effect: The lush wetland and glen areas reduce energy demand for air-conditioning by an estimated 3,840 kWh per day—equivalent to 145 household units—saving 724 tonnes of CO₂ annually.
• Natural wastewater treatment: Replacing deep treatment plants with constructed wetlands saves approximately 5,000 kWh of electricity per day, reducing emissions by an additional 1,500 tonnes per year.
• Vegetation regeneration: Rehabilitated plant life absorbs an estimated 267 tonnes of CO₂ annually.
• Material reuse: Repurposing concrete for ecological planters prevents the extraction of 735 tonnes of stone and avoids 78 tonnes of CO₂ emissions.

Liyumen Park demonstrates a powerful and scalable alternative to conventional infrastructure—offering a replicable model that addresses flood control, wastewater management, public space, and carbon mitigation in a single integrated system.