Integrating water quantity- and quality-related ecosystem services into water scarcity assessment: A multi-scenario analysis in the Taihu Basin of China

Water scarcity is a growing global concern, resulting from drastic climate and societal changes witnessed over the past few decades. Previous attention has predominantly focused on inadequate water quantity as the main cause of water scarcity, but pollution-induced water scarcity has been largely overlooked. Furthermore, there is a lack of understanding about the effectiveness of policy interventions in mitigating water scarcity and its social impact. To address these knowledge gaps, we developed an ecosystem service-based approach to measure quantity-and quality-related water scarcity by comparing supply of and demand for water provision and water purification services. We also developed several water and land management scenarios to examine their potential in alle-viating water scarcity under different climate conditions and water quality requirements. Our case study in the Taihu Basin of southeastern China identified four types of water scarcity status across different sub-basins, including quantity-based, quality-based, quantity-and quality-based, and no water scarcity. The degradation of water quality in the Taihu Basin has exacerbated the scarcity of clean water supply. Water conservation measures effectively alleviated quantity-based water scarcity, while nitrogen reduction and grain for green (i.e., conversion of cropland into forest land) exhibited similar efficacy in alleviating quality-based water scarcity. Integrating these measures contributed to alleviating both quantity-and quality-based water scarcity. However, the effectiveness of these measures decreased under drier climate conditions and higher water quality re-quirements, highlighting the importance of climate and water quality in determining the magnitude, extent, and severity of water scarcity. The approaches and findings presented here provide new insights into the sustainable management of water resources in the Taihu Basin and other similar basins worldwide.