Blue water: Its distribution and relationship to the river network [version 2]

Blue water, which includes freshwater in reservoirs, lakes, rivers, and aquifers, plays a crucial role in sustaining life on Earth and serves as a direct water resource for human societies. The distribution of blue water resources shows spatiotemporal variations, making it important to comprehensively understand the distribution patterns and influencing factors of blue water resources in river basins. In this study, the normalized runoff was analyzed using methods including stationarity testing, correlation analysis, and variance analysis to explore its spatiotemporal patterns and the relationships with river structure. The results indicate that the normalized runoff time series show stationarity at a global scale and show correlations with river network density and the distance to the nearest downstream sink, but the strength of these correlations varies across different regions on different continents. The normalized runoff also shows variations among river order. Further research could examine predicting blue water availability given information on river network structure and climate.