Governing Water Sustainability Through SDG Interlinkages: Novel Evidence on Climate Vulnerability, Health, Environmental Policy, and Clean Innovation in OECD Countries

ABSTRACT Water sustainability has become a critical challenge within the sustainable development agenda, particularly under increasing climate risks and resource pressures. Despite its central role in Sustainable Development Goal 6 (SDG 6), existing studies largely adopt fragmented and linear approaches, overlooking the interconnected and nonlinear nature of sustainability dynamics. This study addresses this gap by examining the multidimensional effects of climate vulnerability, health conditions, economic development, environmental policy, and clean innovation on water sustainability, proxied by public water supply, across OECD countries over the period 2015–2024. To capture heterogeneity and nonlinearities, panel quantile regression is employed as the main estimation technique, complemented by quantile‐based causality tests and Quantile‐on‐Quantile (QQR) analysis for robustness. The results reveal significant distributional heterogeneity. Economic growth shows a predominantly negative effect, particularly at higher quantiles, indicating persistent scale effects associated with economic expansion. In contrast, climate vulnerability and health conditions exhibit positive but regime‐dependent impacts. Environmental policy stringency becomes positively significant and more effective in higher sustainability regimes, whereas clean innovation displays negative effects across all quantiles. The causality results further confirm asymmetric and bidirectional relationships among the variables. Overall, the findings emphasize the importance of integrated governance, climate‐resilient infrastructure, health‐oriented water policies, and sustainability‐aligned innovation strategies to strengthen sustainable water management and support the integrated achievement of SDGs 3, 6, 8, 9, and 13.