Discerning changes and drivers of water yield ecosystem service: A case study of Chongqing-Chengdu District, Southwest China

Water yield (WY) ecosystem service is an important ecological indicator in assessing water availability and sustainability. Although it was widely acknowledged that WY was mainly driven by land use change and climate factor, the intrinsic driving mechanisms remained unclear. Here, we selected the Chengdu-Chongqing District in Southwest China as the study area, using the InVEST model, structural equation modeling, and scenario analysis to exhaustively reveal the past and future WY changes and contribution rate of driving factors. The results demonstrated that the study area experienced rapid forest expansion and urbanization at the expense of cropland and grassland in the last 30 years. In this region, WY increased by approximately ∼130 mm during 1990–2020, attributed mainly to the contribution of precipitation (>90 %), and secondary to potential evapotranspiration and land use change. It was projected that by the end of the 21st century, WY would increase by about 20 % under SSP585 scenario compared to the historical average. We found that every 100 mm increase of precipitation would produce an additional 62–65 mm of WY, with higher precipitation resulting larger WY coefficient due to energy constraint there. Further, we also found that the elevation factor played a direct and negative role (standardized path coefficient, b = −0.4, p < 0.05) in precipitation, and further indirectly, positively dominated (b = 1.0, p < 0.05) WY. This implied that higher WY was widely occurred in areas with lower elevation. These results highlighted topographic and climatic factors controlling WY in such a basin-featured region, which provided a deeper understanding into ecosystem service science.