Higher-density river discharge observation through integration of multiple satellite data: Midstream Yellow River, China

Abstract

Silty Midstream Yellow River (MYR), characterized by its turbid waters, is currently underserved by a sparse network of gauging stations, which is insufficient for comprehensive flow monitoring. Establishing an extensive gauging network in this region is almost impractical. This study addresses the challenge by estimating discharge at selected ungauged reaches of the MYR, leveraging multiple remote sensing datasets with high spatiotemporal resolutions, complemented by Manning’s Equation. Satellite observation reaches (SORs) were strategically positioned at each small river section between adjacent tributaries, chosen for their variable river width, stable channel terrain, and uniform flow, which are conducive to the application of Manning’s Equation. Hydraulic parameters for 16 SORs were calculated, integrating optical and Synthetic Aperture Radar data with a digital elevation model to derive river width, water surface level, and slope. River bathymetry and bed elevation, not directly observable by satellites, were simulated using an adapted altimetry-assimilated one-dimensional (1D) hydraulic model. The discharge time-series at the SOR locations was subsequently retrieved and validated against observed discharges at existing gauges, demonstrating high accuracy with Nash-Sutcliffe Efficiency values ranging from 0.704 to 0.779 and R² values from 0.773 to 0.925. This study effectively expanded discharge observations at ungauged river reaches, increasing the number of observation sites from three to sixteen and achieving an average monitoring interval of 2.7 days per site. The enhanced river discharge observations facilitated by remote sensing provides more granular water and sediment flux data, which is instrumental for future hydrological research and soil conservation planning within large river basins.