Comprehensive Benefit Valuation of Sponge City Development: A Case Study of Daguan Wetland Park, Guangzhou

Against the background of Sponge City development, the ecological performance of constructed wetlands has been widely demonstrated, yet their comprehensive benefits still lack an integrated accounting framework and empirical assessment. Taking Daguan Wetland Park in Guangzhou as a case study, this paper develops a monetary valuation framework for its comprehensive benefits. Based on real estate market transaction data from 2025, the 0–1500 m buffer zone is defined as the treatment group and the 1500–3000 m buffer zone as the control group. Sensitivity analyses are further incorporated to identify the net land value premium attributable to the wetland. At the same time, annual ecological flow benefits, including rainwater reuse, runoff control, and operation and maintenance cost savings, are quantified. These benefits are separately accounted for from the land value appreciation component, and a benefit–cost ratio (BCR) is calculated. The results show that over the 10-year operating period following the completion of Daguan Wetland Park, the project generated a total comprehensive benefit of CNY 581.8435 million, of which direct ecological benefits amounted to CNY 19.1644 million. Spatial spillover benefits amounted to CNY 562.6791 million, accounting for approximately 98% of the total benefits. Enterprises exhibited an implicit willingness-to-pay rate of 27.38% for the wetland-related ecological location premium, and the benefit–cost ratio reached 2.45. These findings confirm the significant economic viability of investing in urban sponge infrastructure. This study provides the first empirical valuation of a Sponge City wetland in a high-risk urban flooding area of the Greater Bay Area and offers strategic insights and practical references for the development and market-oriented investment of sponge infrastructure.