Estimating river discharge from data assimilation of swath altimetry into a regional hydrodynamic model

Abstract

Satellite remote sensing data has been used to complement river hydraulic data measured by existing in situ gage networks. The upcoming Surface Water and Ocean Topography (SWOT) is a swath mapping radar altimeter and will provide estimates of large (50-100 m width) river discharge globally by measuring water storage changes in terrestrial surface water bodies. The SWOT is scheduled to launch in November 2022. This study focuses on evaluating the possibility of estimating SWOT-based river discharge using a data assimilation algorithm coupled with a regional hydrodynamic model in the Nakdong river basin (24,000 km2), South Korea. Synthetic SWOT observations are generated by sampling the regional hydrodynamic model with the SWOT instrument design. The hydrodynamic model is forced by surface runoff and sub-surface runoff from Noah-MP version 3.6. land surface model, which is established within the NASA Land Information System framework. MERRA-2 metrological reanalysis from NASA/GMAO is utilized as a forcing for the open-loop simulation. In addition, added value of the local precipitation datasets from the Korean Meteorological Administration and Global Telecommunication System are forced for the control run and synthetic SWOT observation generation. This work supports an effective hydrological monitoring system to incorporate space-borne continuous regional river discharge and provide important information on water resources in South Korea.