Heterogeneous impacts and spillover effects of green innovation network and environmental regulation on water use efficiency: A spatiotemporal perspective from 269 cities in China.

• China's water use efficiency (WUE) has strong regional heterogeneity. • The green innovation network (GIN) has a U-shaped relationship with WUE. • This paper demonstrates the applicability of Porter hypothesis in WUE. • Environmental regulation has a strong positive spatial spillover effect on WUE. Water is a strategic resource for economic and social development, and exploring the evolutionary mechanism of water use efficiency (WUE) is key to realizing regional sustainable development. This study takes 269 cities in China from 2008 to 2019 as the research unit and uses the spatial econometric model to reveal the spatial effect of the green innovation network (GIN) and environmental regulation on WUE. The results show that WUE in China shows a fluctuating upward trend and has strong spatiotemporal heterogeneity and spatial correlation characteristics. The high-value areas of WUE are mainly concentrated in the Shandong Peninsula urban agglomeration, and the low-value areas are mainly distributed in the middle reaches of the Yangtze River. The GIN and WUE have a significant U-shaped relationship, indicating that only by breaking through " Valley of Death" and "Darwinian Sea" can the GIN exert "network effects" and "technological effects" to improve WUE. Environmental regulation has a significant positive spillover effect on WUE, which verifies the rationality of the Porter hypothesis in WUE. In addition, the impact of the GIN on WUE has strong spatiotemporal heterogeneity, so when strengthening the GIN connection, the rebound effect must be prevented from negatively affecting WUE. [ABSTRACT FROM AUTHOR]