CryoSat-2 altimetry for river level monitoring — Evaluation in the Ganges–Brahmaputra River basin

The performance of CryoSat-2/SIRAL altimetry for river level monitoring is investigated by using river levels retrieved from Ganges and Brahmaputra. A key concern for the CryoSat-2 orbit has been its long repeat period of 369 days, which is usually undesirable for river and lake monitoring. However, the results from the method developed in this study involving virtual stations show that the CryoSat-2 data can indeed be used for such monitoring by utilizing the high spatial coverage and the sub-cycle period of 30 days. The results show that it is possible to capture the peak flow occurring during late summer due to monsoonal precipitation and the melting of snow in the Himalayas. The evaluation of CryoSat-2 river levels is performed by comparing with Envisat data in terms of annual signals and amplitudes. The obtained annual amplitudes agree well with the Envisat data, although CryoSat-2 exhibit larger differences. For five virtual stations in the Brahmaputra River, the mean difference between the obtained amplitudes is ~ 10 cm, whereas the mean phase difference is less than 2.7 days. A virtual station in the Ganges River shows a phase difference of around 5 days and a difference in amplitude of 2 cm.