Comment on nhess-2022-101

Abstract

River discharge and water level data play a vital role for various hydrological applications worldwide. However, limited availability of in-situ data has drawn attention towards using remote sensing techniques to monitor river flow. Indeed, multi-mission satellite altimetry data has been used to generate stage-discharge rating curves through power-law relations and empirical methods. The validation of hydrodynamic model-based rating curves is missing. We investigate the potential of available altimetry series (Jason 2, Jason 3, Saral/AltiKa, Sentinel 3A and Sentinel 3B) over Mahanadi River to validate the estimated rating curves at virtual stations. The hydrodynamic model (HEC-RAS) was developed and 07 virtual stations were identified for Mahanadi River from Boudh to Mundali Barrage. During calibration (July–October, 2018) and validation (July–October, 2018), Root Mean Square Error (RMSE) and Nash-Sutcliffe Efficiency (NSE) between simulated and in-situ water level was found to be (0.46 m, 0.83) and (0.45 m, 0.76) respectively. The calibrated and validated model was used to generate rating curves at virtual stations. The RMSE ranging between 27 cm to 88 cm was observed between simulated and altimetry water levels, specifying the potential of all the altimeters with varying specifications to validate the rating curves. The rating curves estimated at virtual stations provide a cost-effective tool for monitoring river flows at additional locations, producing discharge time series for various hydrological applications and assessing of contribution of lateral tributaries.