Water Quality and Quantity Regulation Effect

• Based on 76 sponge cities in China, a meta-analysis method was used to evaluate the relationship between climate, topography, underlying surface conditions, and construction area with the increase in annual total runoff control rate and SS removal rate;
• Under the comprehensive conditions of an average annual rainfall of approximately 1000 mm, high vegetation coverage, sufficient soil fertility, a slope of ≤2%, and a soil permeability coefficient of 100–200 m/d, the runoff control benefits of sponge cities can be significantly improved, especially in northern China, where the weight calculation of comprehensive benefits is 25.5%;
• In central North China, the significant benefits of SS removal reached a weight of 21.4%.

Data Source:

Yuan Y, Zhang Q, Chen S, & Li,Y. Evaluation of comprehensive benefits of sponge cities using meta-analysis in different geographical environments in China. Science of The Total Environment, 2022, 836: 155755.

• Based on the geodesign framework, the effectiveness of sponge city projects in water pollution control and flood regulation was evaluated for Harbin Qunli Wetland Park, Sanya Mangrove Eco-Park, and Quzhou Luming Park. The results showed that sponge city projects significantly reduced pollutant outputs, with nitrogen and phosphorus reduction rates reaching 11%-18%. After further expansion of green infrastructure, the control capacity could be enhanced by an additional 9%-15%. For example, in Sanya Mangrove Eco-Park, nitrogen output decreased from 4421 kg/year to 3710 kg/year (a 14% reduction), while phosphorus output decreased from 348 kg/year to 240 kg/year (a 45% reduction).
• In terms of flood regulation, sponge city projects effectively reduced surface runoff by 0.4%-6.3%, with further reductions of 0.8%-2.9% observed after expansion. For instance, runoff volume in Harbin Qunli Wetland Park decreased by 1.7%, while Sanya Mangrove Eco-Park saw a reduction of approximately 2.93%.
• The results indicate that sponge city projects enhance water resource management and urban flood prevention capabilities by optimizing green infrastructure networks, providing sustainable solutions for climate change adaptation.

Data Source:

Li, Y.; Kim, Y. Analysis of Effects of Sponge City Projects Applying the Geodesign Framework. Land. 2022, 11, 455.

Assessment of Wastewater Toxicity Reduction

• Compared with traditional urban sewage treatment processes, the effluent from constructed wetlands exhibits lower toxicity than secondary and tertiary effluent, effectively mitigating the hazards caused by residual pollutants and controlling the formation of toxic byproducts.
• A study evaluating the toxicity reduction effects of six constructed wetlands in central and eastern China showed a reduction in wastewater cytotoxicity by 54%-86%. Among these, the combined wetlands outperformed single-mode surface flow wetlands in terms of toxicity removal efficiency.
• The evaluation results enhance the understanding of constructed wetlands’ role in achieving safe wastewater reuse, providing evidence for further improving their toxicity reduction performance.
• The constructed wetlands studied include:
  Haikou Meishe River Greenway and Fengxiang Park: https://www.turenscape.com/project/detail/4772.html
  Qian'an Sanli River Ecological Corridor: https://www.turenscape.com/project/detail/4558.html
  Yichang Canal Park: https://www.turenscape.com/project/detail/4638.html
  Jinhua Puyang River Ecological Corridor: https://www.turenscape.com/project/detail/4646.html
  Handan Garden Expo – Clear Channel:https://www.turenscape.com/project/detail/4825.html
  Jinhua Lanxi Yangtze River Ecological Park: https://www.turenscape.com/project/detail/ 4833.html

Data Source:

Gao X, Yang J, Song J, Wu S, Li M, Li J, Chen X, Qin H, Luan H, Chen Z, Yu K, Liu W. Toxicity removal from contaminated water by constructed wetlands assessed using multiple biomarkers in human stem cell assays. Sci Total Environ. 2024 Mar 15;925:171682. doi: 10.1016/j.scitotenv.2024.171682.