SWOT-Driven Global River Discharge Reconstruction: A Novel Framework for Streamflow Analysis under Climate Change

River streamflow is fundamental to hydrological science, providing essential insights for freshwater resource management, flood and drought control, and riverine ecosystem preservation. However, conventional field measurements are predominantly limited to major rivers and downstream reaches, while hydrological models heavily depend on these observations for calibration and training. The declining availability of in-situ data significantly impedes global streamflow mapping, particularly for thousands of ungauged rivers, thereby constraining our understanding of hydrological processes.

The Surface Water and Ocean Topography (SWOT) satellite, launched in 2022, provides unprecedented observations of water surface elevation (WSE), river width, and slope for global rivers, enabling discharge estimation without traditional gauging data. It employs six well-established algorithms to optimize unobserved flow law parameters (FLPs), including friction coefficients and referenced cross-sectional areas. These FLPs effectively characterize hydraulic properties for individual river reaches, with accuracy continuously improving through prolonged SWOT monitoring periods. This critical information enables the reconstruction of river discharges using historical satellite observations and fundamental flow laws (e.g., Modified Manning’s equation) with SWOT-derived FLPs.

By applying the estimated FLPs to nadir altimeter virtual stations (e.g., Jason and Sentinel-3), our methodology enables global river discharge estimation using altimetric WSEs alone. This approach facilitates comprehensive river streamflow reconstruction dating back to early satellite operations, demonstrates gauge-independent generalization capability, and establishes a novel paradigm for tracking discharge dynamics by integrating historical observations with SWOT-based discharge. Validation by the SWOT science team indicates uncertainty levels below 30% for most river reaches. Our framework establishes a foundation for analyzing global river responses to climate change and hydrometeorological extremes, offering significant potential for enhancing resilience to hydrological variations in a changing climate.