How can SWOT derived water surface elevations help calibrating a distributed hydrological model?

Abstract

The launch of the Surface Water and Ocean Topography (SWOT) mission with the Ka-band Radar Interferometer (KaRIn) sensor has opened up new possibilities for river monitoring and hydrological/hydrodynamic model calibration with 2 to 4 observations per cycle (∼21 days) over the Indian region. The present study examines the potential of discharge derived from SWOT-type WSE for hydrological model calibration. Results are presented for Modelo de Grandes Bacias (MGB) hydrological/hydrodynamic model for calibration using in-situ, SWOT-like discharge and SWOT-like discharge with 30 % variance data. The results of proxy SWOT discharge indicate NSE ranging between 0.72 and 0.97 across 11 stations over the Mahanadi River basin in India, with enhanced NSE during high-flow (Monsoon) conditions compared to low-flow (non-monsoon) conditions. It is also inferred that MGB hydrological model, when calibrated against in-situ, SWOT-like discharge and SWOT-like discharge with 30 % variance, shows a close NSE value for discharge simulation with a 4.7 % and 7.9 % reduction in the NSE value at the outlet of the Mahanadi River basin. The simulated discharge after calibration for both scenarios closely matches during monsoon as well as during non-monsoon seasons, which strongly suggests that the SWOT discharge has significant potential in the river discharge monitoring and can help calibrating the hydrological model with fidelity over the large river basin like Mahanadi river basin, hence potentially improving the discharge monitoring after mission’s lifetime.