This session concerns measurements and estimations of water levels, water extent, 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 also cover aspects on assimilation of remote sensing together with in situ data within hydrodynamic models are welcome and encouraged.

The monitoring of river water levels, river discharges, water bodies extent, storage in lakes and reservoirs, 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 is contributing in an increasing way, as they provide near real time measurements as well as long homogeneous time series to study the impact of climate change, over various scales from local to regional and global.

During the past twenty-nine years a large number of satellites and sensors has been developed and launched allowing to quantify and monitor the extent of open water bodies (passive and active microwave, optical), the water levels (radar and laser altimetry), the global water storage and its changes (variable gravity). River discharge, a key variable of hydrological dynamics, can be estimated by combining space/in situ observations and modelling, although still challenging with available space borne techniques.

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 Sentinel-3A/B missions are maturing. The future SWOT mission, to be launched in 2021, will open up many new hydrology-related opportunities.