CoAuthors

Ritesh Agrawal (ISRO, India); Amit Dubey (ISRO, India); Aditya Chaudhary (ISRO, India); Anup K Mandal (ISRO, India); Neeraj Agarwal (ISRO, India); Adarsh M. S. (IIT Delhi, India); Taha Aawar (IIT Delhi, India); Dhanya C. T. (IIT Delhi, India); Rashmi Sharma (ISRO, India); R. P. Singh (ISRO, India)

SWOT mission is expected to be the first satellite to provide high-resolution global surface water elevation maps. These radar interferograms over water surfaces would enable a wide range of research opportunities especially in the field of land hydrology. In this work, satellite observations (river level, width) along with an integrated hydrological modelling scheme is utilized to estimate the river discharge over the Narmada site that we are aiming to establish as a calibration site for the upcoming SWOT mission. In the first step, the Virtual stations (VS) were selected over the SWOT and Sentinel-3A/3B orbit along with the available CWC gauge stations, for the estimation of river discharges. Water level time series was generated using Sentinel-3 radar altimeter data after correcting geophysical range corrections like dry tropospheric correction, wet tropospheric correction, ionosphere correction for the period 2016-2020. Virtual Station near Hoshangabad was selected for calibration of the derived discharges based upon the availability of nearby CWC measured level/discharge information (nearly 5 km apart); the present gauge also falls within a km of proposed SWOT nadir track. The retrieved water levels over the VS were found to be fluctuating between 281.76 meter to 287.97 meter. The in-situ field trip was carried out in synchronous with altimeter overpass on 8 February 2020. Acoustic Doppler current profiler (ADCP) and DGPS profiles were taken during the experimentation. The estimated river width and discharge was found to be 510.29 m and 107.75 m3/s respectively. SWOT hydrology simulator along with RiverObs and prior reach database SWORD-v5 was used for testing the module for estimation of water surface elevation profiles. The input for the simulator like water level and river width shape files were generated using existing Sentinel-3 altimeter data and Landsat-8 optical dataset respectively. The inundated areas within a stretch of nearly 10 km was found to be fluctuating between 404 to 575 Ha during the period 2014-2020, where the maximum extent was taken from the wetbnd layer from national Wetland inventory and assessment (NWIA) dataset. The derived surface water elevation, river width and slope information were used for estimating the river discharge at the desired location using rating curve information. CWC in-situ dataset was also used for deriving the water stage-discharge relationship and calibrating the model. WRF Hydrological modelling was also set up over the basin for estimation of river discharge over targeted locations of altimeter tracks and CWC stations. The derived river discharge will provide a valuable dataset for numerical ocean models and a better understanding of the hydrological cycle over the Indian region.