Understanding the Earth’s water cycle and land-surface processes requires seamless access to high-quality, harmonised in situ observations. This joint presentation introduces three key international data centres: the Global Runoff Data Centre (GRDC), the International Soil Moisture Network (ISMN), and the GEMS/Water Data Centre (GWDC). -GRDC provides standardized long-term river discharge data essential for climate change assessments and water management. - ISMN acts as the primary global repository for in situ soil moisture measurements, critical for validating satellite products and refining Earth system models. - GWDC provides freshwater quality monitoring data from surface and groundwaters to support large-scale status assessments and supports the global reporting of Sustainable Development Goal (SDG) indicator 6.3.2. This presentation will demonstrate how these data services empower users, ranging from researchers to policymakers, by providing "Analysis-Ready Data." The centres enhance data interoperability, bridging the gap between local ground observations and global environmental monitoring. They ensure that authorities and the scientific community have the robust, harmonized data necessary to address global water challenges.