The latest planetary boundaries assessment underscores that freshwater systems are facing escalating risks. At the same time, they remain a priority on the political agenda, as reflected in the Sustainable Development Goals. Water security offers a comprehensive framework for disentangling the complex relationships between freshwater resources and human development.WS encompasses economic, environmental, and hazard dimensions, yet existing measurement approaches suffer from heterogeneity, limited comparability, and poor temporal coverage. This paper advances WS research in three ways. First, we present an original, reproducible global WS assessment at 0.5°×0.5° resolution from 2003–2019, integrating Earth observations and statistical data to capture multidimensional risks and resources. Second, we apply both weak and strong sustainability frameworks to WS, revealing substantial discrepancies in estimated security levels and threat areas, with weak sustainability systematically overestimating WS. Third, we examine how economic development and governance interact with WS at the national scale, distinguishing size and intensity effects and identifying institutional conditions that shape outcomes. Our analysis reveals that the weak sustainability approach systematically overestimates both the quality and progression of WS when compared with the strong sustainability approach, a discrepancy primarily attributable to the underlying embeddedness assumption. The mechanisms analysis highlight the non-linearities linking economic and political development to WS levels.