Satellite radar and lidar altimeters observed seasonal variation in water level of Ganga River

Monitoring of water level change for any river basin plays vital role to understand its water cycle and driving factors. The satellite observations using advanced sensors facilitate to monitor large continental water bodies at fixed spatial-temporal resolution. In the present work, satellite radar and laser altimeters (Jason-2/3, SARAL/AltiKa, Sentinel-3A/3B, Sentinel-6, ICESat-2, CryoSat-2) are utilized to examine the variation of long-term water level of Ganga River. The accuracy assessment of altimetry-based water levels is carried out using in-situ observations at selected river reaches. It is found that, the quality of the altimetry observations has been improved over period of time with no marginal impact of temporal resolution on their accuracy. Lidar-based altimeters having small footprint were able to examine the water level at relatively narrow river reaches. Further, we analyzed the intra-annual and inter-annual variation of the water level from upstream to downstream end virtual stations of the selected Ganga River reaches. The combined use of radar and lidar altimeters data enables detection of long-term water cycle at large to narrow river reaches with improved spatial-temporal resolution.