The monitoring of river water levels, river discharges, water bodies extent, storage in lakes and reservoirs, flooding and floodplain dynamics plays a key role in assessing water resources, understanding surface water dynamics, characterizing and mitigating water related risks and enabling integrated management of water resources and aquatic ecosystems.

While in situ measurement networks play a central role in the monitoring effort, remote sensing techniques are expected to contribute in an increasing way, as they can provide with homogeneous and near real time measurements over large areas, from local to basin wide, regional and global.

This session concerns measurement and/or estimation of water levels, water extent, flooding, water storage and water discharge of surface water bodies such as rivers, lakes, floodplains and wetlands, through combined use of remote sensing and in situ measurements. Contributions that cover aspects on assimilation of remote sensing together with in situ data within hydrodynamic models are welcome and encouraged.

During the last ten to twenty years a large number of satellites and sensors have been developed and launched that allow to quantify and monitor the extent of open water bodies and flooding (passive microwaves, active microwaves, optical), the water levels (radar and laser altimetry), the global water storage and its changes (GRACE). River discharge, a key variable of hydrological dynamics, although still out of reach with available space borne techniques, can be estimated by combining space/in situ observations and modelling.

Traditional instruments contribute to long-term water level monitoring and provide baseline databases. Scientific applications of more complex technologies like the SAR altimetry on CRYOSAT-2 and further Sentinel-3 missions will also emerge. At the end of the decade the evolution of the technology up to the future SWOT mission will open up many new hydrology-related opportunities.