The mediating effect of urban water system climate resilience in the impact of sponge city pilot policy on ecological welfare

Water system safety is critically linked to socio-economic development and ecological welfare (EW). Under climate change, there is an urgent need to develop effective solutions that synergistically enhance urban water system climate resilience (UWSCR) and human welfare. The sponge city pilot policy (SCPP) implemented in China from 2015 to 2016 highlighted the importance of urban water systems for climate adaptation. Utilizing panel data from 280 prefecture-level and above cities in China from 2010 to 2020, this study adopts the multi-period difference-in-difference model to evaluate the effectiveness and heterogeneity of SCPP on improving EW, and examines the mediating role of UWSCR in the impact of SCPP on EW. The research conclusions are as follows: (1) SCPP has significantly improved EW. (2) SCPP is more effective in cities with medium heavy rain hazard, high or medium drought hazard, medium water resources endowment and high or low economic development level. (3) UWSCR, the direct objective of SCPP implementation, has played a mediating role in the effect of SCPP to enhance EW, indicating that SCPP is an effective policy instrument for synergizing climate adaptation and welfare improvement. Finally, suggestions were put forward to optimize SCPP. This study provides a scientific basis for promoting sustainable urban development under climate change.