Trevor Wilkerson (Montana State University, United States); Cascade Tuholske (Montana State University, United States)

Sound water management relies on consistent and reliable data on the timing and quantity of freshwater resources—information that is currently unevenly distributed, often with a paucity of streamflow measurements in developing economies. The Surface Water and Ocean Topography (SWOT) satellite mission represents a significant advancement in our ability to measure and understand the storage and movement of freshwater across the Earth and within the global water cycle. In addition to its scientific gains, SWOT offers essential socio-technical insights that can support better-informed water resource management for an individual country and across international borders. By enhancing observational capacity, SWOT has the potential to improve decision-making and reduce conflict over shared water resources. In this study, we integrate data from SWORD (SWOT River Database), the Global Stream Gage database, and global gridded population datasets to estimate the number of people living within 5 km and 20 km of SWORD river segments that lack a streamflow gage. Globally, SWOT can provide streamflow measurements to 1.65 billion people who live within 5km of a stream without a gage, and 3.64 billion who live within 20km of a stream without a gage. At the continental scale, Africa, Asia, and South America are projected to benefit most from increased streamflow observations enabled by SWOT. At the national level, countries such as Guatemala, Iran, and Sudan see up to a 100% increase in streamflow observation capacity. When these analyses are applied to transboundary (international) river basins, they reveal that SWOT could significantly enhance data availability in regions in the Glob(international) ersheds with high potential for hydropolitical tension (Nile, Amu Darya). Incorporating SWOT-derived products into water planning and policy offers a promising path forward—reducing uncertainty, increasing adaptability, and especially benefiting areas with limited existing monitoring systems.