Application of CryoSat-2 altimetry data for river analysis and modelling

Availability of in situ river monitoring data, especially of data shared across boundaries, is decreasing, despite growing challenges for water resource management across the entire globe. This is especially valid for the case study of this work, the Brahmaputra Basin in South Asia. Commonly, satellite altimeters are used in various ways to provide information about such river basins. Most missions provide virtual station time series of water levels at locations where their repeat orbits cross rivers. CryoSat-2 is equipped with a new type of altimeter, providing estimates of the actual ground location seen in the reflected signal. It also uses a drifting orbit, challenging conventional ways of processing altimetry data to river water levels and their incorporation in hydrologic–hydrodynamic models. However, CryoSat-2 altimetry data provides an unprecedentedly high spatial resolution. This paper suggests a procedure to (i) filter CryoSat-2 observations over rivers to extract water-level profiles along the river, and (ii) use this information in combination with a hydrologic–hydrodynamic model to fit the simulated water levels with an accuracy that cannot be reached using information from globally available digital elevation models (DEMs) such as from the Shuttle Radar Topography Mission (SRTM) only. The filtering was done based on dynamic river masks extracted from Landsat imagery, providing spatial and temporal resolutions high enough to map the braided river channels and their dynamic morphology. This allowed extraction of river water levels over previously unmonitored narrow stretches of the river. In the Assam Valley section of the Brahmaputra River, CryoSat-2 data and Envisat virtual station data were combined to calibrate cross sections in a 1-D hydrodynamic model of the river. The hydrologic–hydrodynamic model setup and calibration are almost exclusively based on openly available remote sensing data and other global data sources, ensuring transferability of the developed methods. They provide an opportunity to achieve forecasts of both discharge and water levels in a poorly gauged river system

Dataset (CryoSat-2 altimetry data over Brahmaputra River, river masks, model cross sections) used in Schneider et al., 2017. doi:10.5194/hess-2016-243

Dataset used in Schneider, R., Nygaard Godiksen, P., Villadsen, H., Madsen, H., Bauer-Gottwein, P., 2017. Application of CryoSat-2 altimetry data for river analysis and modelling. Hydrol. Earth Syst. Sci.rticle. doi:10.5194/hess-2016-243 The dataset contains CryoSat-2 satellite altimetry data over the Brahmaputra River from 2010 to 2013 River masks, derived from Landsat NDVI imagery, used to filter the CryoSat-2 data Results from the cross section calibration described in Schneider et al., 2017 All data is provided as a .zip file which includes a README.txt with more details on the data